BER analysis of amplify-and-forward relaying FSO systems using APD receiver over strong atmospheric turbulence channels

In this paper, we theoretically analyze the performance of amplify-and-forward (AF) serial relaying free-space optical (FSO) systems using avalanche photodiodes (APD) and subcarrier quadrature amplitude modulation (SC-QAM) over strong atmospheric turbulence channels modelled by gamma-gamma distribution. Closed-form expression for average bit error rate (BER) of system is theoretically derived talking into account APD shot noise, thermal noise as well as the impact of atmospheric loss and turbulence. The numerical results show that using AF relay stations can extend the transmission distance and help to improve performance of FSO system significantly when compared with the direct transmission. Moreover, the selection of APD gain value is indispensable to the system performance. The proposed system could be achieved the best performance by selecting an optimal APD gain value. In addition, the optimal value of APD gain also significantly depends on various conditions, such as link distance, the number of relay stations and APD receiver noise

Misalignment fading effects on the ACC performance of relay-assisted MIMO/FSO systems over atmospheric turbulence channels

The continuous development of internet of things (IoT) technology enables many devices to be interconnected through the external environment. Meanwhile, 5G technology provides an enhanced quality of services with high data transmission rates, requiring IoT implementation in the 5G architecture. Free-space optical communication (FSO) is considered a promising technique that can provide high-speed communication links, so FSO is an optimal choice for wireless networks to fulfill the full potential of 5G technology, providing speeds of 100 Gb/s or more. By implementing 5G features in IoT, IoT coverage and performance will be enhanced by using FSO models. Therefore, the paper proposed and investigated the multiple-input and multiple-output/free-space optical communication (MIMO/FSO) model using subcarrier quadrature amplitude modulation (SC-QAM) and relay stations over atmospheric turbulence channels by log-normal and gamma-gamma distribution under different turbulence conditions. The performance is examined based on the average channel capacity (ACC), which is expressed in terms of average spectral efficiency (ASE) parameters while changing the different parameters of the model. The mathematical formulas of ACC for atmospheric turbulence cases are calculated and discussed the influence of turbulence strength, the different number of relay stations, misalignment effects, and different MIMO configurations

CONNECTING MATHEMATICS AND PRACTICE: A CASE STUDY OF TEACHING EXPONENTIAL FUNCTIONS

There is a need for teaching exponential functions to show the necessity for a better match between the knowledge of exponential functions in high schools with the practical application of it in fields. In this research, a teaching process was built in association with teaching situations to show students the relationship between mathematics and real life. The research sample included 76 students in high schools in Vietnam. Additionally, two problems of compound interest and population growth were integrated and were the main research instruments. Data were collected, including student work, and they were analyzed qualitatively. The results showed that students had improved their problem-solving skills and saw the relationship between mathematics and practice. Furthermore, there were some recommendations suggested for textbook authors and teachers. Article visualizations

Analysis on the performance of reconfigurable intelligent surface-aided free-space optical link under atmospheric turbulence and pointing errors

Free-space optical (FSO) communication can provide the cost-efficient, secure, high data-rate communication links required for applications. For example, it provides broadband Internet access and backhauling for the fifth-generation (5G) and the sixth-generation (6G) communication networks. However, previous solutions to deal with signal loss caused by obstructions and atmospheric turbulence. In these solutions, reconfigurable intelligent surfaces (RISs) are considered hardware technology to improve the performance of optical wireless communication systems. This study investigates the pointing error effects for RIS-aided FSO links under atmospheric turbulence channels. We analyze the performance of RIS-aided FSO links influenced by pointing errors, atmospheric attenuation, and turbulence for the subcarrier quadrature amplitude modulation (SC-QAM) technique. Atmospheric turbulence is modeled using log-normal distribution for weak atmospheric turbulence. Several numerical outcomes obtained for different transmitter beam waist radius and pointing error displacement standard deviation are shown to quantitatively illustrate the average symbol error rate (ASER)

VIBRATION ANALYSIS OF CROSS-PLY LAMINATED COMPOSITE DOUBLY CURVED SHALLOW SHELL PANELS WITH STIFFENERS

In this paper, the analytical solution for the cross-ply laminated composite double curved shell panels with stiffeners is presented. Based on the smeared stiffeners technique and the first shear deformation theory (FSDT), the motion equations are derived by applying the Hamilton’s principle. The Navier’s solution for the simply supported boundary condition for all edges is presented. The numerical results are verified with the known results in the literature. The effects of the number of stiffeners, dimensions of stiffeners, and lamination scheme of cross-ply laminated composite doubly curved shell panels on the natural fundamental frequencies are investigated

Average symbol error rate analysis of reconfigurable intelligent surfaces based free-space optical link over Weibull distribution channels

Optical wireless communication (OWC) enables wireless connectivity using ultraviolet bands, infrared or visible. With its advantages features as high bandwidth, low cost, and operation in an unregulated spectrum. Free-space optical (FSO) communication systems are near terrestrial as a communication link between transceivers, the link is line-of-sight and successfully transmitted optical signals. Nevertheless, the optical signals transmissions over the FSO channels bring challenges to the system. To overcome the challenges posed by the FSO channels, the most common technique is to use relay stations, the most recent is the reconfigurable intelligent surfaces (RISs) technique. This study introduces a Weibull distribution model for a free-space optical communication link with RISs assisted, the parameter used to evaluate the performance of the system is the average symbol error rate (ASER). The RISs effect is examined by considering the influence of the transmitter beam waist radius, shape parameter, aperture radius, scale parameter, and signal-to-noise ratio on the ASER

The 3-3-1 Model with Arbitrarily Charged Leptons

The gauge  model based on $\mathrm{SU}(3)_C\otimes \mathrm{SU}(3)_L\otimes \mathrm{U}(1)_X$  group with arbitrarily electric charged exotic leptons is presented. The mass eigenvalues and eigenstates for  neutral gauge bosons are presented in the general form. We show that in the 3-3-1 models, there always exists triple Higgs self-coupling. The lepton number operator is also presented

Statistical estimation of frictional coefficients of faults based on a structural dataset in the Tuy Hoa–Vung Tau Region, Viet Nam

This study estimates the shear friction coefficient from shear friction angles for the prediction of slip tendencies in the Tuy Hoa–Vung Tau region of Southern Vietnam. A dataset consisting of measured data of 355 fractured planes, striations, and unconformities in coastal areas as well as 239 offshore faults was analyzed based on the principles of statistical probability. As a result, 138 friction angles for the onshore and offshore faults were calculated based on shear fracture conjugate pairs. The goodness-of-fit test was used to define the probability distribution of the friction angles, which had a normal distribution. The acceptable average of friction angles for the onshore region with a reliability of more than 95% were in the range of 25.8–31.5°, which corresponds to frictional coefficients of 0.48–0.61. The acceptable average friction angles for the offshore region were relatively low at 23–31°, which corresponds to a frictional coefficient of 0.42–0.60. Owing to the heterogeneity of the fault system, the median value (19.12°) should be used as the lowest threshold value for slipping faults at all conditions. The recommended applicable average friction angles are 28.65° and 27° for the onshore and offshore regions, respectively. The estimation of the frictional coefficients is highly reliable, and it can be applied to other subsurface resource exploitation projects within the study area

PHÁT HIỆN VI KHUẨN PASTEURELLA MULTOCIDA GÂY BỆNH TỤ HUYẾT TRÙNG Ở CỪU PHAN RANG BẰNG KỸ THUẬT PCR

Pasteurellosis is an infectious disease causing severe damage to livestock and poultry since it leads to animals’ death, including sheep of all ages. In this study, we developed a sensitive, specific and accurate PCR method for detecting P. multocida in Phan Rang sheep using FKMT1/RKMT1 primers targeted to the KMT1 gene of P. multocida. The PCR-based method was used to detect the KMT1 gene from 104 copies of the KMT1-bearing plasmid. The method’s specificity was demonstrated by the successful amplification of KMT1 from the mixture containing other DNA of Gram-negative bacteria, such as E. coli or M. haemolytica. In particular, with the present method, we successfully detected P. multocida with crude DNA obtained from P. multocida or nasal swabs of pasteurellosis-suspected sheep samples treated in a TE buffer containing 0.1% TritonX-100. This is the first report on using a PCR-based method for detecting P. multocida from Phan Rang sheep, and it can serve as the basis for an effective procedure to diagnose pasteurellosis in sheep.Tụ huyết trùng là một bệnh truyền nhiễm có thể gây thiệt hại nghiêm trọng cho chăn nuôi gia súc, gia cầm nếu không được chẩn đoán và điều trị kịp thời. Vì vậy, trong nghiên cứu này chúng tôi đã phát triển phương pháp PCR có độ nhạy, độ đặc hiệu và độ chính xác cao để phát hiện sự có mặt của vi khuẩn P. multocida, một trong những tác nhân gây bệnh tụ huyết trùng trên cừu Phan Rang. Gen KMT1 của vi khuẩn P. multocida được nhân lên bằng cặp mồi đặc hiệu FKMT1/RKMT1 ở nồng độ khoảng 104 bản sao của plasmid mang gen đích. Phản ứng PCR không bị ảnh hưởng khi có mặt DNA của một số vi khuẩn Gram âm khác như E. coli hay M. haemolytica. Đặc biệt, với phương pháp PCR, chúng tôi đã phát hiện sự có mặt của vi khuẩn P. multocida từ mẫu DNA thô thu được bằng xử lý mẫu vi khuẩn/mẫu dịch ngoáy mũi của cừu nghi nhiễm bệnh trong đệm TE chứa 0,1% TritonX-100 mà không cần tinh sạch DNA tổng số. Đây là nghiên cứu đầu tiên công bố một phương pháp xác định sự có mặt của P. multocida trên cừu Phan Rang và là cơ sở để xây dựng quy trình chẩn đoán hiệu quả nhằm góp phần kiểm soát bệnh tụ huyết trùng trên đối tượng này