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حرية الوصول المقاله
1 - Amplitude Symmetry Detection for Interfering Signals in CNC Satellite Communications
Habib Alizadeh Mohsen Rezaee Morteza BabaeiSatellite communications technology developed rapidly and plays important role in communication networks. In the meantime, CNC satellite communication has received much attention due to its high spectral efficiency. However, the analysis of this type of communication si أکثرSatellite communications technology developed rapidly and plays important role in communication networks. In the meantime, CNC satellite communication has received much attention due to its high spectral efficiency. However, the analysis of this type of communication signal in non-cooperative receivers is associated with many challenges due to the nature of time-frequency overlap. The proposed methods in this field have been developed assuming either symmetry or asymmetry in the amplitude of the two interfering signals. However, a reliable method to detect the amplitude symmetry in the non-cooperative receivers is missing in the literature. Thus, in this article, the symmetry or asymmetry of the amplitude of time-frequency overlapping signals of these type of communications has been analyzed using higher-order statistics. For this purpose, the mathematical relationships of higher-order statistics for the model of time-frequency interfering signals received in the non-cooperative receiver have been developed. Then, the appropriate decision function is defined based on different ratios of higher-order statistics of the received signal. This decision function is used to detect amplitude symmetry or asymmetry in time-frequency overlapping signals for CNC communication. The simulations show that the decision-making function based on the sixth and fourth ratio cumulants is a reliable metric, such that the probability of correct classification at signal-to-noise levels higher than 25dB for BPSK modulation is more than 80%, and for QPSK modulation is more than 90%. تفاصيل المقالة -
حرية الوصول المقاله
2 - Investigation of Strain Gradient Theory for the Analysis of Free Linear Vibration of Nano Truncated Conical Shell
A.R Sheykhi Sh Hosseini Hashemi A Maghsoudpour Sh Etemadi HaghighiIn this paper the nano conical shell model is developed based on modified strain gradient theory. The governing equations of the nano truncated conical shell are derived using the FSDT, and the size parameters through modified strain gradient theory have been taken into أکثرIn this paper the nano conical shell model is developed based on modified strain gradient theory. The governing equations of the nano truncated conical shell are derived using the FSDT, and the size parameters through modified strain gradient theory have been taken into account. Hamilton’s principle is used to obtain the governing equations, and the shell’s equations of motion are derived with partial differentials along with the classical and non-classical boundary conditions. Galerkin’s method and the Generalized Differential Quadrature (GDQ) approach are applied to obtain the linear free vibrations of the carbon nano cone (CNC). The CNC is studied with simply supported boundary condition. The results of the new model are compared with those of the classical and couple stress theories, which point to the conclusion that the classical and couple stress models are special cases of modified strain gradient theory. Results also reveal that rigidity of the nano truncated conical shell in the strain gradient theory is greater than that in the modified couple stress and classical theories respectively, which leads to an increase in dimensionless natural frequency ratio. Moreover, the study investigates the effect of the size parameters on nano shell vibration for different lengths and vertex angles. تفاصيل المقالة -
حرية الوصول المقاله
3 - تاثیر انبساط طولیBall Screw در محورهای خطی، بر حرکت محورهای چرخشی و درستی هندسی قطعه کار در ماشینهای فرز CNC پنج محور با کله گی چرخشی و آپشن RTCP فعال
امیر علی نقی زاده میثم خاکیدر هنگام ماشینکاری بخشی از حرارت ایجاد شده بر اثر عمل کنش لبه های برنده ابزار نسبت به قطعه کار که به ماشین منتقل می شود و علاوه بر آن، اصطکاک ایجاد شده در حرکت مداوم Ball Screwها در داخل Nut که بر اثر جابجا شدن محورهای ماشین بوجود می آید، باعث انبساط ابعادیBall Screw خو أکثردر هنگام ماشینکاری بخشی از حرارت ایجاد شده بر اثر عمل کنش لبه های برنده ابزار نسبت به قطعه کار که به ماشین منتقل می شود و علاوه بر آن، اصطکاک ایجاد شده در حرکت مداوم Ball Screwها در داخل Nut که بر اثر جابجا شدن محورهای ماشین بوجود می آید، باعث انبساط ابعادیBall Screw خواهد شد. به دلیل طویل بودن و نسبت طول به قطر زیاد، انبساط ایجاد شده در راستای طول Ball Screw حایز اهمیت خواهد بود. زیرا در پی هرحرکت اعمال شده در برنامهNC، با توجه به اختلاف اندازه میان خط قبلی برنامه تا خط کنونی، علاوه بر جابجایی اصلی یک جابجایی اضافی نیز به خاطر انبساط Ball Screw، انجام می پذیرد. در ماشینهای CNC پنج محور، علاوه بر تاثیر مستقیم انبساط طولیBall Screw محورهای خطی بر درستی هندسی قطعه کار، تاثیر غیر مستقیمی نیز وجود دارد که با توجه به آپشن RTCP(چرخش ابزار حول نقطه مرکزی اش)، برای جابجایی محورهای چرخشی نمایان می گردد. در RTCP فعال، مرکز ابزار در فضا ثابت وبجای آن، مرکز محورهای چرخشی متحرک می باشند. در این حالت برای جبران جابجایی های ابزار، در اثر حرکت محورهای چرخشی، محورهای خطی جابجا خواهند شد. در این مقاله تاثیر مستقیم وغیر مستقیم انبساط طولی Ball Screw ها بر روی درستی هندسی قطعه کار با استفاده از روابط تحلیلی-ریاضی مورد بررسی قرار گرفته واز نتایج آن می توان برای کنترل تطبیقی با موضوعیت عنوان مقاله در ماشینهای CNC پنج محور بهره برد. تفاصيل المقالة -
حرية الوصول المقاله
4 - گاهنگاری نسبی سفال‌های قوشاتپه شهریری
حسن درخشی علیرضا هژبری نوبری بهمن فیروزمندی شیرهجینیسفال به عنوان یک ماده فرهنگی، مدرک مهمی در گاهنگاری نسبی و مطلق محوطه‌ها و مقایسه آن‌ها با یکدیگر است. بر مبنای مطالعات تطبیقی سفال‌های شاخص قوشاتپه شهریری از منظر فرم و تزیین و آنالیز تعدادی از نمونه‌ها با کمک ترمولومینسانس که مکمل روش نخست بود؛ این نتیجه حاصل گردید که أکثرسفال به عنوان یک ماده فرهنگی، مدرک مهمی در گاهنگاری نسبی و مطلق محوطه‌ها و مقایسه آن‌ها با یکدیگر است. بر مبنای مطالعات تطبیقی سفال‌های شاخص قوشاتپه شهریری از منظر فرم و تزیین و آنالیز تعدادی از نمونه‌ها با کمک ترمولومینسانس که مکمل روش نخست بود؛ این نتیجه حاصل گردید که از نظر زمانی فازهای تحتانی محوطه مذکور اواخر نوسنگی و گذر آن به کالکولیتیک قدیم را نشان می‌دهد که صرف نظر از این مسأله مقایسه تطبیقی سفال‌های قوشاتپه نشـان داد که محوطه روابط فرهـنگی و اجتماعی پایداری به‌ویژه با حوزه دریاچه ارومیه از همین مقطع زمانی پایان نوسنگی تا دوره‌های بعدی داشته است. تفاصيل المقالة -
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5 - Molecular Simulation of Hydrogen Adsorption onto Single-Walled Carbon and Boron-Nitride Nano-Cones
Muhammad Shadman Lakmehsari Tahereh KalatehIn this paper, we have studied the hydrogen adsorption onto CNCs and BNNCs nano-cones using GCMC simulations. The effects of length and cone apex angle on adsorption property have been investigated. Our results show that with increasing the pressure and decreasing the c أکثرIn this paper, we have studied the hydrogen adsorption onto CNCs and BNNCs nano-cones using GCMC simulations. The effects of length and cone apex angle on adsorption property have been investigated. Our results show that with increasing the pressure and decreasing the cone length and cone apex angle except for CNC-300˚, the hydrogen adsorption onto the BNNCs and CNCs was increased. It was also found that BNNCs can uptake more hydrogen in comparison with CNCs at the same thermodynamically conditions. Further, more hydrogen adsorption can be achieved in both CNCs and BNNCs with 240˚apex angle. This finding attributed to high surface area as well as strong interactions between hydrogen molecules and respected nano-cones. Also, results of hydrogen adsorption with unit of mol/m3 are corresponded of the energy of hydrogen adsorption. تفاصيل المقالة -
حرية الوصول المقاله
6 - Analysis of Orthotic Insoles Manufacturing for Treating Flatfoot Using Smart Orthotic Insole in Comparison with Traditional Methods
Behzad Karimkhani Sayed Hasan MirtalaieIn this research, the anomaly of flatfoot was initially introduced, followed by an examination of both traditional and new methods for designing and manufacturing orthotic insoles suitable for it. Regarding this matter, the design and construction of orthotic insoles us أکثرIn this research, the anomaly of flatfoot was initially introduced, followed by an examination of both traditional and new methods for designing and manufacturing orthotic insoles suitable for it. Regarding this matter, the design and construction of orthotic insoles using a stamp as a traditional method was introduced, and subsequently, the step-by-step elucidation of new methods, including foot scanning and the utilization of smart orthotic insoles in designing and manufacturing insoles suitable for flatfoot, was carried out. In both of these new methods, the design and construction of appropriate orthotic insoles involved the transfer of information obtained from the foot to relevant software and their subsequent processing. This research, while explaining the mentioned methods, described how to use engineering design software in designing and manufacturing orthotic insoles suitable for flatfoot. In conclusion, the results obtained from all three manufacturing methods were presented and compared to ascertain the advantages and disadvantages of each approach. تفاصيل المقالة -
حرية الوصول المقاله
7 - Investigating Predictive Maintenance Strategies for CNC Machine Tools in the Industry 4.0 Era
Fionn FoleyThis research compares different approaches for achieving precise predictive maintenance (PdM) results from CNC machine tools. For smaller enterprises, it is crucial to be able to upgrade their existing industrial machines with industry 4.0 systems, as the global market أکثرThis research compares different approaches for achieving precise predictive maintenance (PdM) results from CNC machine tools. For smaller enterprises, it is crucial to be able to upgrade their existing industrial machines with industry 4.0 systems, as the global marketplace becomes more competitive. The evolution of the Internet of Things (IoT) and the creation of cyber-physical systems (CPS) in the industry has enabled big data generation. New maintenance methodologies have emerged where decisions are driven by mathematical models and data analysis. In this study, a low-cost strategy is used as a baseline to establish system accuracy. Results are then compared to a more comprehensive strategy outlining the potentials of these retrofit predictive maintenance (PdM) systems. Numerous data modeling techniques were employed to increase system accuracy while focusing on the remaining useful life (RUL) of the cutting tool. Through analysis of the selected strategies favorable correlation is evident between predicted results and physical tool wear, optimal accuracy of 95.68% is achieved by utilizing hybrid data modeling techniques. The study highlights the possibilities for enterprises looking to adopt PdM strategies and consequently capitalize on the potential of Industry 4.0. تفاصيل المقالة -
حرية الوصول المقاله
8 - Development of a QFD-based expert system for CNC turning centre selection
Kanika Prasad Shankar ChakrabortyComputer numerical control (CNC) machine tools are automated devices capable of generating complicated and intricate product shapes in shorter time. Selection of the best CNC machine tool is a critical, complex and time-consuming task due to availability of a wide range أکثرComputer numerical control (CNC) machine tools are automated devices capable of generating complicated and intricate product shapes in shorter time. Selection of the best CNC machine tool is a critical, complex and time-consuming task due to availability of a wide range of alternatives and conflicting nature of several evaluation criteria. Although, the past researchers had attempted to select the appropriate machining centres using different knowledge-based systems, mathematical models and multi-criteria decision-making methods, none of those approaches has given due importance to the voice of customers. The aforesaid limitation can be overcome using quality function deployment (QFD) technique, which is a systematic approach for integrating customers’ needs and designing the product to meet those needs first time and every time. In this paper, the adopted QFD-based methodology helps in selecting CNC turning centres for a manufacturing organization, providing due importance to the voice of customers to meet their requirements. An expert system based on QFD technique is developed in Visual BASIC 6.0 to automate the CNC turning centre selection procedure for different production plans. Three illustrative examples are demonstrated to explain the real-time applicability of the developed expert system. تفاصيل المقالة
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