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To ensure food security in the face of climate change has been a major issue for both developing and developed countries. Since world population is increasing with geometric progression and has been estimated to be nine billion by the end of 2050. The situation could be more aggravated to due to transformation of agricultural land to non-agricultural purposes. Bangladesh is the one of the best example of climate change vulnerable countries of the world. Though it’s total production has been soared up from independence due to high yielding varieties and better management practices. However, climate change will exert negative impact on crop productivity of the country. So to maintain growth of crop productivity, climatic variability study could be helpful to determine policy options and research need. We have focused on simulation study for analyzing eight major crops production performance using historic climate data (temperature, rainfall and sunshine hour) collected from Bangladesh Meteorological Department. As a simulation software, we will use MATLAB. Using the data, we’ll look for the best performance of each crops. If we can find out the best performance of production ration of a crop, we can then predict that, the maximum production can be achieved by having these variables. World’s climate is changing, so keeping this in mind, we need to go ahead for achieving maximum production in agricultural sector to support the growing number of population. We hope that, it is possible to produce a better simulated performance to enhance the agricultural sector using Fuzzy logic.

We propose a highly sensitive hollow core photonic crystal fiber (HCPCF) for liquid sensing in the terahertz (THz) region. Asymmetrical rectangular shaped air holes in the cladding region along with Topas glass as a background material is used to get high sensitivity and low confinement loss. The full vector finite element method (FEM) is used to calculate relative sensitivity and other parameters of the proposed liquid sensor where frequency range is taken from 1 THz to 2 THz. The strut distance variations are also studied in this study to find out minimum strut length to make the proposed sensor fabrication friendly. Numerical analysis shows the maximum relative sensitivity of 91.42% for water, 92.55% for acetic acid and 94.03% for chloroform at optimal conditions along with the minimum confinement loss of 1.06 × 10−9cm−1 for water, 2.02 × 10−10cm−1 for acetic acid and 1.39 × 10−11cm−1 for chloroform. To the best of our knowledge, the proposed HCPCF sensor shows maximum relative sensitivity for liquid.

Purpose: The purpose of the study is to identify the Prevalence of Low Back Pain and Associated factors among the Nurses. Objectives: To identify the prevalence of low back pain and its associated factor among the nurses of a selected hospital at Dhaka, determine the socio demographic characteristics of the study population, find out characteristics of various complain and associated factors among the low back pain nurses, find out the association of the various complain with associated risk factors for nurses with low back pain. Methodology: The study was conducted by using of Quantitive method. 70 participants are selected and this. Quantitive study conducted in Dhaka Medical College and Hospital, which is a government organization, located in Dhaka. Participants were selected by purposive convenience sampling. All data collected through face-to face interview by using a structured research question. Descriptive statistics is used for data analysis. Result: The study was conducted on 70 participants. Among 70 participants, 17 (24%) participants were male and 53 (76%) were female. Participants in between 21-30 years 18, participants in between 31-40 years 39, participants in between 41-50 years 12, participants in between 51-60 years 1. The Chi-square value was 9.630 and P value was 0.022. So the result was significant that indicate there was association between low back pain and age ranges of the participants. Conclusion: From the result of the study it is found that most of the nurses are suffering with various low back pain associated complication as they don’t maintained the proper lifestyle. Key words: Low back pain, Nurses, Prevalence, Associated factor.

Surface plasmon resonance (SPR)–based structures are finding important applications in sensing biological as well as inorganic samples. In SPR techniques, an angle-resolved reflection (R) profile of the incident light from a metal-dielectric interface is measured and the resonance characteristics are extracted for the identification of the target sample. However, the performance, and hence the applicability of these structures, suffers when the weight and concentration of the target samples are small. Here, we show that SPR-based sensors can create strong magnetism at optical frequency, which can be used for the detection of target samples instead of using the conventional R profiles, as the magnetic resonance varies depending on the refractive index of the target sample. Using scattering parameters retrieval method, we computationally find out the effective permeability (μeff) of a SPR sensor with a structure based on Kretschmann configuration, and use it to calculate the performance of the sensor. A comparison with the conventional technique that uses R profile to detect a target sample shows a significant increase in the sensor performance when μeff is used instead.

A longitudinal assessment of the prevalence of posttraumatic stress symptoms (PTSS) and risk factors is indispensable for further prevention and/or treatment. The longitudinal web-based survey enrolled 1,164 college students in China. Measured at two time points (February and August 2020), PTSS, demographic information, adverse childhood experiences (ACEs), resilience and self-compassion information were collected to explicate the prevalence and predictors of PTSS concurrently and over time. Results showed that although PTSS generally declined throughout the 6 months after the outbreak of COVID-19, the prevalence remained relatively high. Resilience and self-compassion negatively predicted PTSS concurrently and longitudinally. While subjective family socioeconomic status (SES) and ACEs at Wave 1 did not predict PTSS under COVID-19 at Wave 1, but both significantly predicted PTSS at Wave 2. Findings implicate potential targets for detecting and intervening on symptoms of trauma in this vulnerable population.

We demonstrate the design and simulation of a long range four-channel wavelength division multiplexing-passive optical network (WDM-PON) operating at 40 Gb/s (4 × 10 Gb/s) in downstream transmission for undersea wireless optical communication. The proposed model consists of two separate subsections between the optical transmitter and receiver. The first subsection consists of the central office and 50 km long feeder fiber for transmitting the optical signal from a distant base station to the 1 × 4 optical demultiplexer located at the sea shore. The second subsection comprises 500 m distributed fiber from the 1 × 4 optical demultiplexer to the terminal point placed at the bottom of the sea and 15–20 m optical wireless channel inside sea water. Simulation results confirmed successful transmission of optical signals from the 50 km distant optical transmitter to the optical receiver located maximum 15 m inside the sea water with a signal-to-noise ratio of ∼20.96 dB, bit error rate of ∼1.55 × 10−8, and quality factor of ∼5.584. The eye diagram at the receiving end also exemplifies quality downstream data transmission at a rate of 10 Gb/s per channel. In addition, we compare the simulation results of the four-channel 40 Gb/s WDM-PON system with a four-channel WDM-PON system operating at 4 Gb/s (4 × 1 Gb/s). Simulation results confirm maximum reach of 17.5 m inside sea water at a cost of significant reduction in data rate. Furthermore, we analyze the system availability of the proposed WDM-PONs and find convincing results for high-speed secured data transmission under water.

We propose a perfectly square lattice photonic crystal fiber (PCF) which shows high birefringence and negative dispersion. To set up high asymmetry in the core, dual line imperfection is considered where the fill fraction ratio and defect air hole diameter exhibit significant impact on dispersion and birefringence. Numerical analyses of guiding properties of the proposed PCF are done using finite element method with perfectly matched layer boundary condition from 1.2 to 1.8 μm wavelength. The optimized square lattice PCF presents high birefringence of 2.48 × 10−2 and dispersion of −777.66 (ps/nm.km) at 1.55 μm wavelength. In addition, the proposed PCF offers ultra-low confinement and insertion loss at 1.55 μm wavelength. Moreover, −0.45 (ps/nm2.km) dispersion slope and 0.0045 nm−1 relative dispersion slope are observed at 1.55 μm wavelength. Additionally, the proposed PCF maintains dispersion and birefringence variation of ±30 (ps/nm.km) and ±0.00001 between 1.5 and 1.6 μm wavelength ranges, respectively. Furthermore, the proposed PCF shows high quality factor and low bit error rate at 10 dBm input power. We believe the proposed square lattice PCF can be deployed in wavelength division multiplexing based optical fiber transmission system for wide-band dispersion compensation.

Our study proposes a technique to enhance light extraction efficiency of light emitting diodes (LEDs) by incorporating various micro-/nanolens arrays (MNLAs) on the substrate layer, which in turn increases the external quantum efficiency (EQE) of the LEDs. To simulate the LEDs, we utilized the finite difference time domain method. To achieve a white LED, we inserted a thin layer of NiO at the interface between the n-type ZnO and the p-type GaN. The basic n-ZnO/NiO/p-GaN heterojunction-based LED exhibited an EQE of 10.99% where the effective refractive index of the LED structure was 1.48. The EQE was further increased by engraving various planoconvex or planoconcave MNLA on the top surface of the substrate layer. A maximum EQE of 12.4% was achieved for convex-1 type (lens height of 0.5 μm and radius of 0.4 μm) elliptical lens engraved LED where the effective refractive index was 1.4. In addition, the peak electroluminescence (EL) light intensity of convex-1 lens-based LED was twice than the light intensity observed in basic LED. Because of excellent EL spectrum and significant amount of light throughout the visible spectrum, the proposed convex-1 structure-based LED can be considered as a prospective candidate for white LED.

We have designed a Photonic Crystal Fiber (PCF) to achieve high birefringence optical property in the terahertz (THz) frequency region. Air holes look like rectangular shape in cladding area and elliptical air hole in the center zone are considered for the proposed PCF. To identify loss characteristics of the proposed PCF, effective material loss (EML) and confinement loss also have been studied in this paper. The commercial optical properties analyzer, COMSOL Multiphysics 5.3a software has been used for numerical analysis of the designed PCF. To obtain the optimal PCF structure properties, we have varied the elliptical shaped air holes major axis length and adjacent ellipse pitch distance. Numerical analysis shows the maximum birefringence of 0.0921 and minimum confinement loss of $$1.36\, \times 10^{-4}\ \hbox {cm}^{-1}$$ for the proposed PCF. We hope that this highly birefringent PCF will contribute in the field of polarization filter, bio-sensing and terahertz communication devices.

Metformin and Thiazolidinediones are insulin sensitizers used as the first-line treatment of PCOS, which are recently being examined for their extensive beneficial impacts at biochemical and molecular level of body function in Polycystic ovary syndrome. Therefore, purpose of this review is to compare the effectiveness of Metformin and Thiazolidinediones on vascular endothelial function in PCOS. MEDLINE (1966- October 2018), CINAHL (1982 to October 2018), Cochrane Central Register of Controlled Trials and Cochrane Menstrual Disorders and Subfertility Group trials register (October 2018) and Google Scholar were searched electronically without language restriction. Three Randomized controlled trials (RCTs) were selected with a total of 90 participants comparing effect of Metformin (Intervention) to Thiazolidinediones (Comparator) with an outcome on endothelial function among women with PCOS. In results, Meta-analysis shows no statistically significant difference on endothelial-dependent vasodilation between Metformin and Thiazolidinedione (p value= 0.59 at 95% CI - 1.31, 0.74).

Background: Geographic information science (GIS) has established itself as a distinct domain and incredibly useful whenever the research is related to geography, space, and other spatio-temporal dimensions. However, the scientific landscape on the integration of GIS in COVID-related studies is largely unknown. In this systematic review, we assessed the current evidence on the implementation of GIS and other geospatial tools in the COVID-19 pandemic. Methods: We systematically retrieved and reviewed 79 research articles that either directly used GIS or other geospatial tools as part of their analysis. We grouped the identified papers under six broader thematic groups based on the objectives and research questions of the study- environmental, socio-economic, and cultural, public health, spatial transmission, computer-aided modeling, and data mining. Results: The interdisciplinary nature of how geographic and spatial analysis was used in COVID-19 research was notable among the reviewed papers. Although GIS has substantial potential in planning to slow down the spread, surveillance, contact tracing, and identify the trends and hotspots of breakdowns, it was not employed as much as it could have been. This review not only provided an overarching view on how GIS has been used in COVID-19 research so far but also concluded that this geospatial analysis and technologies could be used in future public health emergencies along with statistical and other socio-economic modeling techniques. Our systematic review also provides how both scientific communities and policymakers could leverage GIS to extract useful information to make an informed decision in the future. Conclusions: Despite the limited applications of GIS in identifying the nature and spatio-temporal pattern of this raging pandemic, there are opportunities to utilize these techniques in handling the pandemic. The use of spatial analysis and GIS could significantly improve how we understand the pandemic as well as address the underserviced demographic groups and communities.

We propose a surface plasmon resonance (SPR) glucose sensor where a graphene mono-layer is used with controllable optical property by applying a gate voltage. We show that the gate voltage to the graphene mono-layer can increase the light absorption, and hence, the sensitivity of the proposed glucose sensor significantly. We find that the sensitivity and figure-of-merit of the proposed sensor increase by 21.48% and 49.57% when a 20-V gate voltage is applied to the graphene mono-layer compared to that when there is no gate voltage applied to the graphene mono-layer. We present a linear regression analysis for measuring the blood sugar level (BSL) using the proposed sensor that shows a highly reliable performance of the proposed sensor. We also present the effects of temperature on the proposed sensor performances. We find that the error in the detection of BSL remains within 4.75% on average and within 7.40% in the worst-case scenario when temperature varies by ± 10 °C from a reference 25 °C. Comparisons of the proposed sensor with several state-of-the-art sensors show a significantly enhanced behavior, as well as the error induced due to the change in temperature is much smaller than that of 15%, which is used as an allowable error limit for off-the-shelf glucose meters.

The development of technology has become faster and more people are engaging with technology for various purposes. As a result, the usage of data is increasing with the rapid growth of technology. Nowadays,’s ensuring data security has become a major challenging factor for the service providers. Various techniques are implemented to increase performance and security for data communication. In this paper, a method is proposed using Ron Rivest, Shamir, and Adleman (RSA) algorithm and Diffie–Hellman (DH) algorithm. RSA algorithm is used for encryption and decryption purpose. DH is used for exchanging generated keys. Also, a password protection mechanism is applied in the proposed algorithm. The interesting part in password system is that for every decryption password, there will be a decrypted text. The system won’t tell you that you have entered wrong password. Decrypted correct text will appear only if anyone enters the correct password, which was used during encryption. The proposed algorithm is simulated and the results are presented, which represent the evaluation of algorithm within a secure and efficient way for ensuring secure data communication.

Solid core circular and octagonal photonic crystal fibers (CPCF and OPCF) are proposed for analyzing different guiding properties such as dispersion, effective mode area, nonlinearity, and confinement loss from 0.8 to 2.6 µm wavelength. The proposed structures use three different types of background materials: SF10, BK7, and silica. Moreover, the fill fraction is varied by changing the diameter of the air hole where the lattice pitch is unchanged. The proposed PCFs show a high negative dispersion with low confinement loss and small effective mode area. In the proposed design, the finite element method with a perfectly matched layer absorbing boundary condition is used. At 1.8 µm wavelength with 0.6 fill fraction, the maximum negative dispersion of − 922.5 p s / ( n m . k m ) is observed for CPCF when the background material is SF10. In addition, at this particular wavelength, the confinement loss is observed to be very small. Moreover, − 560.12 p s / ( n m . k m ) dispersion is found for the similar condition at 1.55 µm wavelength. On the other hand, using BK7 as the background material, − 706.77 p s / ( n m . k m ) dispersion is found at 1.55 µm wavelength for CPCF. Results also imply that CPCF shows better performance than OPCF for a wide wavelength range. Furthermore, at 1.55 µm wavelength, silica-based glass exhibits maximum dispersion, whereas increasing wavelength flint type glass shows the similar result. Analyzing different guiding properties of PCFs has significant impact on broadband dispersion compensation applications, especially using SF10.

Background: Novel coronavirus disease (COVID-19) was first identified in China, which eventually became a major global health concern due to its pathogenicity and widespread distribution around the world. Despite a growing interest in COVID-19 across populations, little is known about the current state of knowledge on COVID-19, which can inform how much is known about this problem. This bibliometric study evaluated the contemporary scientific literature to assess the evolution of knowledge on COVID-19, identify the leading research stakeholders, and analyze the conceptual areas of knowledge development in this domain. Methods: Bibliometric data on COVID-19 related studies published until April 1, 2020, were retrieved from three major databases within Web of Science core collection. Further, a quantitative evaluation was conducted to assess the characteristics of the current studies and create visualizations of knowledge areas in COVID-19 research by statistical and text-mining approaches using bibliometric tools and R software. Results: A total of 422 citations were retained in this study, including journal articles, reviews, letters, and other publications. The mean number of authors and citations per document was 3.91 and 2.47, respectively. Also, the top ten articles, authors, and journals were identified based on the frequencies of citations and publications. Networks of contributing authors, institutions, and countries were visualized in maps, which highlight discrete developments in research collaborations. Major areas identified through evaluating keywords and text data included genetic, epidemiological, zoonotic, and other biological topics associated with COVID-19. Conclusions: Current status of COVID-19 research shows varying progress in different areas of knowledge. However, more research should be conducted in less-explored areas, including socioeconomic determinants and impacts of COVID-19. Also, research collaboration should be encouraged among global nations to mobilize shared resources. Lastly, the global knowledge base should be strengthened for evidence-based decision-making preventing and addressing the COVID-19 pandemic and aftermath around the world.

Modern world is blessed by technical development. Developing agricultural sector has become a great demand nowadays, because people are increasing and the land is decreasing. Various methods are applying to improve the production in the agricultural sector. Among foods, rice is one of the major foods consumed by different types of people all over the world. So, in this research, fuzzy logic is used to analyse the Aman rice production. We considered the main factors related to Aman rice (BR23 Aman) productions are temperature, rainfall and area. We analysed the production estimation using collected data and an estimation is presented by using the fuzzy-based simulated result. We have calculated coefficient of variation (CV) for the three factors, and the result indicates that, the CV for temperature is 49.12% whereas CV value for rainfall and area is 29.68% and 22.79% respectively, which indicates BR23 Aman as temperature-sensitive.

Graphene has impressive features that make it an exceptional material for sophisticated applications in next generation electronics and opto-electronics devices. This peremptory material has attracted researchers’ attention in various fields of recent advancement since its discovery in 2004. Its applied fields are increasing day by day. This two-dimensional material (2D) is using mellifluously for the development in different types of devices in the field of optics, photonics, light emitting diode (LED), medical diagnosis, sensing, and so on. In this review, the relevant optical properties and the applications areas with available results in various fields are discussed. Again, the optical conductivity of strained graphene is reviewed in a wavelength related regime that depends on strain modulus and position with field arrangements. Graphene shows a saturation and reverse saturation process due to the increase of light intensity. In addition, strong absorption is observed from the visible to mid-infrared (MIR) wavelength range. Moreover, the application areas of graphene including optics, photonics, plasmonics, mode-locked laser, optical modulator, etc., and the comparison of various results obtained from different sources are presented.

This article reviews the recent progress in optical sensors using photonic crystal fiber (PCF) technology, which is newly adopted beyond conventional optical fibers (OFs) due to their unique geometric structures. PCFs have some exceptional properties. It will focus the most conversant sensing application areas with their consistent parameters and perception. Numerous PCF sensors are available in day-to-day world. Researchers and technologists are working on PCFs with more than 15-20 application areas. In this article, sensing applications in physical and bio- chemical with their diverse types are reviewed recent times. Physical sensors as temperature, curvature, torsion, vibration, pressure, refractive index, evanescent; where the bio-chemical sensors as humidity, gas, pH, liquid etc. has been reviewed in this article. The review shows that, most physical sensing applications are varied with their different structures and parameters.

We demonstrate the design and simulation of intense light beam (ILB) achieved by concave microlens engraved lenticular fibers. Both single and multiple microlenses of spherical and elliptical shapes have been incorporated just inside the fiber core. The ILBs have been designed using commercial OptiFDTD simulator. We investigate the average light intensity and beam profile at several locations including near field, far field-1, and far field-2 after the end face of the optical fibers. For single microlens, elliptical-shaped microlens engraved optical fibers show higher light intensity compared to spherical-shaped microlens engraved fibers. Light intensity at the output of the single-microlens incorporated fibers shows increasing trend with the increase of the radius of curvature (R) of the microlenses, where the highest light intensity has been achieved for R = − 17.65 μm. For microlens array engraved lenticular fibers, 9-lens model having R = − 8 μm has shown the highest light intensity. Due to the interference of light coming out from neighbor microlenses, the diffraction pattern, i.e., beam profile at any particular plane, is different for different arrangements of the microlenses. The proposed lenticular fibers are expected to have a wide range of applications in micro-optical systems, especially in biomedical engineering.

In an erbium-doped fiber amplifier (EDFA), erbium ions act as a three-level system. Therefore, much higher pump energy is required to achieve the population inversion in an erbium-doped fiber (EDF). This higher pump energy requirement complicates the efficient design of an EDFA. However, efficient use of the pump power can improve the EDFA performance. The improved performance of an EDFA can be obtained by reducing the doping radius of the EDF. A smaller doping radius increases pump–dopant interactions and subsequently increases the pump–photon conversion efficiency. Decreasing the doping radius allows a larger proportion of dopant ions, which are concentrated near the core, to interact with the highest pump intensity. However, decreasing the doping radius beyond a certain limit will bring the dopant ions much closer and introduce detrimental ion–ion interaction effects. In this Letter, we show that an optimal doping radius in an EDF can provide the best gain performance. Moreover, we have simulated the well-known numerical aperture effects on EDFA gain performance to support our claim.

In this paper, a dual-core liquid filled photonic crystal fiber coupler (PCFC) with rectangular (RPCFC) and hexagonal (HPCFC) geometry is presented from the 1200 to 1800 nm wavelength range. In the proposed design, super flint (SF10) glass is used as the background material and water, chloroform, and benzene are infiltrated in the dual-core, independently. The properties of the guided modes are studied by the finite difference time domain (FDTD) method with a perfectly matched layer (PML) boundary condition. Results reveal very small confinement loss with a low coupling length and birefringence for the wide wavelength range. At the 1.55 μm wavelength, RPCFC shows 0.000318, 0.000358, and 0.000379 m coupling lengths for the water, chloroform, and benzene filled dual-core, respectively. Additionally, the confinement loss of 1.57×10−7, 1.22×10−7, and 1.05×10−7 db/km is achieved through RPCFC. Moreover, both the PCFCs present a small polarization variation. Therefore, the proposed PCFC models can be used in optical communication systems, and polarization-independent and high temperature-sensitive applications areas.

A very low temperature coefficient (

Chromatic dispersion and confinement loss are two significant issues in the design of photonic crystal fiber. This paper presents a systematic study of these two issues for five rings hexagonal photonic crystal fiber along with its dependence on structure and material used. The values of these two propagation characteristics obtained for different refractive indices and hole diameters reveal that optimization of these two characteristics depend on the application requirements, but not for determining which fiber structure is the best. Photonic crystal fiber structure is modeled using OPTI FDTD 8 simulation software and dispersion as well as loss is plotted by MATHCAD 2000i Professional tool.

We report on the fabrication of nanostructure covered micro holes on the surface of fused silica glass by irradiation with single-beam direct femtosecond laser pulses. Nano-bumps or nano-pillars were formed on the side wall near the surface as well as near the bottom of the micro holes with a diameter down to 100nm. On the top of the nano-bumps, grouped and spherical shaped nanostructures down to 10 nm were observed. Nano-gratings with an average period of 175 nm-200 nm were found at the bottom of the holes, which is less than λ i /2η period (η is the refractive index of the material).

CDMA refers to multiple access method in which the individual terminals uses spread spectrum techniques and occupy the entire spectrum whenever they transmit. This feature makes CDMA different from FDMA and TDMA. In the wireless communication, the Signal to Interference Ratio (SIR) and Bit Error Rate (BER) are the predominant parameter that characterizes the system performance. This paper presented here Standard Gaussian Approximation (SGA) methods presented in the international literature concerning the computation of the SIR and the BER in DS-CDMA systems under perfect and imperfect power control over fading and non-fading channel. The content and conclusions of this paper have driven to take many important decisions by varying different DS-CDMA communication parameters such as processing gain, number of interfering cells, multipath components etc. using SGA techniques. As SGA is analytically developed and is very computationally efficient solution for the system performance estimate in terms of SIR and BER, it helps us to avoid the tedious and cost-inefficient simulations.