1- Introduction

2- Model and principle

3- Results and discussion

4- Conclusions

References

Abstract

As an indirect imaging technique, computational ghost imaging (GI) obtains the object information by calculating the intensity correlation between a series of computer-generated matrices and the corresponding bucket signals, which thereby offers a potential application in optical encryption. Here, we propose a new steganography scheme, called ghost steganography, based on the principle of computational GI. In our ghost steganography scheme, the bucket intensity signals of a secret image are concealed into the ones of a non-secret image by applying a non-conspicuous number integration process. To further increase the security, we introduce RSA cryptography to encode the integrated bucket signals after the steganography process. Simulation and experiment results fully demonstrate the feasibility of our optical ghost cryptography and steganography scheme. Our work paves a way to the application of GI in steganography and also enriches the knowledge of symmetric and asymmetric optical cryptography.

Introduction

Ghost imaging (GI), also known as correlated imaging, is an indirect imaging modality which obtains the object information from the intensity fluctuation correlation of two beams. One beam, called object beam, going through the object, is measured by a bucket detector. The other beam, called reference beam, interacting without the object, is detected by a spatially resolved camera. GI was firstly achieved with entangled photon pairs experimentally in 1995 [1], and later extended into the classical region with various thermal light sources [2–11]. Different from the two-detector GI, Shapiro proposed the computational GI in 2008 [12], which generated the active illumination patterns by using the spatial light modulator instead of passive measurements of reference beam. Similar to the single-pixel camera technique [13], computational GI can recover the object image with only a single-pixel detector [14,15], which largely simplifies the experimental setup. Meanwhile, the correlation between the computer-generated random matrix and the object beam intensity of computational GI offered a potential application in optical encryption [16-30]. To increase the efficiency and security of optical encryption based on GI [16], different methods are proposed and developed, including gray-scale and color encryption [17], multiple-image encryptions [18,26,29], specific phase masks schemes [22,25,27,30], XOR operation scheme [24].

1- Introduction

2- Theory and proposed scheme

3- Result and discussion

4- Conclusion

References

Abstract

This paper reveals an analytical perception of electro-optically tunable cascaded Kerr-lens using RbTiOPO4 (RTP) crystal where the advantageous properties of the crystal have been studied to mitigate the limitations of KTiOPO4 (KTP) and BaB2O4 (BBO) in intracavity high power laser generation. An external electric field application to the z-direction of RTP is introducing a phase mismatch condition leading to a nonlinear phase shift within propagating optical waves. Based on simulated endeavors, a maximum effective nonlinear refractive index of ± 1.4053 × 10−13 cm2 /W is calculated by developing a phase shift of ∓4.6 rad. In contrast, KTP and RTP both have almost similar optical properties but due to certain special features like higher damage threshold, less walk-off angle etc., RTP is firmly accepted for high power applications. Additionally, this article is augmented to analyze the self-focusing and defocusing phenomenon owing to the nonuniform distribution of radial intensity of the propagating Gaussian beam. To the best of author’s knowledge, the present analysis manifests the superior performance of RTP that may pave the way to devise a configurable lens analogous to Kerr-lens having an electro-optically tunable focal length.

Introduction

In the past several decades [1–5], cascaded second-order nonlinearity has played a vital role in the generation of cascaded Kerr lens mode-locking [6] that is nothing but a successive combination of two second harmonic generation (SHG) processes (χ(2):χ(2) development) that yields an intensity-dependent large phase mismatch in propagating fundamental waves. Accordingly, the nonlinear phase shift because of the non phasematched condition is also relative to the intensity of the incident beam that is analogous to Kerr medium (χ(3) nonlinearity) [6,7]. Moreover, the performance of this feature may enlarge the third-order nonlinearity of a medium having weak third-order coefficient [8] which is grander than the natural third-order nonlinearity [5] associated with the Kerr electro-optic effect as well. As a consequence of that, cascaded second-order nonlinearity equivalent to third-order nonlinearity [2] plays a significant role in several areas like transistor action [9], electro-optical detection [10], electro-optic switching [11], selffocusing and self-defocusing [9] etc. [12–15]. Although different techniques are emphasized to develop cascaded second-order nonlinearity using various types of crystals where problems like undesirable cavity loss, inaccuracy of incident beam angle, etc [5,16]. have occurred that deters a controllable desired output. In recent years [17,18], an analytical method has been introduced named “electro-optically tunable cascaded nonlinearity” in an exceedingly bulk anisotropic crystals like Potassium Titanyl Phosphate (KTiOPO4, KTP) and Beta Barium Borate (BaB2O4, BBO), etc.

I- Introduction

II- Experiment

III- Analysis of Experimental Results

IV- Conclusion

References

Abstract

As one of the most important external insulation equipment in power system, insulators play an important role in transmission and distribution network. In this paper, qualitatively and quantitatively analysis of the contaminated elements on the surface of artificial contaminated insulators and natural contaminated insulators were carried out by Laser-Induced Breakdown Spectroscopy (LIBS). For artificial contaminated insulators, Na and Al elements can be used to characterize the equivalent salt deposit density (ESDD) and non-soluble deposit density (NSDD) levels respectively. For natural contaminated insulators, there are differences in spectral intensity of contaminated elements with different contamination years. And with the increase of the contamination years, the spectral intensity of the Si, Fe, Ca, Al, K and Na elements also have an increasing trend. Insulator samples under 4 contamination levels were classified based on the principal component analysis (PCA) algorithm. Dimension reduction analysis was conducted by extracting 6 excitation spectra (Si, Fe, Ca, Al, K, Na) which can represent contamination information. The 2 principal components with the largest contribution rate were obtained and the principal component scores of each spectrum were calculated. The research results showed that the spectral sample points have obvious convergence phenomenon according to the contamination level of the insulators. Compared with the commonly used methods for judging contamination level, LIBS technology has the advantages of easy operation, no sample processing and high sensitivity. Therefore, the combination of LIBS technology and PCA algorithm can save time and cost and improve the detection efficiency in the field of insulator.

INTRODUCTION

As one of the most important external insulation devices for power system, insulators play an important role in the transmission and distribution networks. With the development of China, the environmental pollution caused by the daily activities of industry and humans is also increasing. The contamination on insulator surfaces will affect its external insulation performance. In severe cases, it will cause flashover, and the flashover on transmission lines will cause large-scale power outage, which will result in power system failure and bring huge economic losses [1]. Therefore, the evaluation of insulator contamination is the basic research work in the field of external insulation of power systems, which is of great significance for the design, operation and mainten.ance of external insulation of power systems. A large number of scholars at home and abroad have conducted a lot of research on insulator contamination detection and achieved a series of outstanding results, which have greatly reducing the power system failure caused by contamination flashover [2,3]. At present, the most common method of measuring contamination is to remove the insulator from the power line and then determine the contamination level by measuring the equivalent salt deposit density and nonsoluble deposit density [4]. However, this method is complicated in operation and needs to be powered off, which is not convenient in practical operation [5]. Reference [6] installed metal electrodes on the surface of insulators, which can determine the contamination degree of insulators by measuring the surface conductivity of insulators when the air humidity is relatively saturated. The ultraviolet discharge pulse signal will appear when the leakage current is generated on the insulator surface. The relevant characteristics of the leakage current can be obtained and the contamination degree can be determined by analyzing the signal with a certain algorithm [7]. However, the exact relationship between the current leakage current and the degree of contamination has not been fully clarified, and the installation of the equipment is also complicated, and the degree of environmental impact is relatively large.

Introduction

Material and methods

Results and discussion

Conclusions

References

Abstract

In nonlinear optics, the soliton transmission in different forms can be described with the use of nonlinear Schrödinger (NLS) equations. Here, the soliton transmission is investigated by solving the NLS equation with the reciprocal of the group velocity b1ðzÞ, the group velocity dispersion coefficient b2ðzÞ and nonlinear coefficient cðzÞ. Two-soliton solutions for the NLS equation are obtained through the Hirota method. According to the solutions obtained, b1ðzÞ and cðzÞ with different function forms are taken to study the characteristics of solitons. The effect of the phase shift on the soliton interaction is discussed, and the non-oscillating soliton amplification, which is transmitted in a bound state, is explored. Parabolic solitons with oscillations are analysed. Moreover, parabolic solitons can be reduced to dromion-like structures. Results indicate that the transmission of solitons can be adjusted with the group velocity dispersion and Kerr nonlinearity coefficients. The phase shift, amplification, oscillation and attenuation of solitons can also be controlled by other related parameters. This work accomplishes the theoretical study of transmission characteristics of optical solitons in spatially dependent inhomogeneous optical fibres. The conclusions of this research have theoretical guidance for the research of optical amplifier, all-optical switches and mode-locked lasers.

Introduction

Solitons have been investigated in such fields as mathematics and physics [1–6]. They can propagate in a long distance without changes in their waveform, velocity and amplitude [7–10]. The soliton phenomena are closely related to nonlinear evolution equation models [11–17]. Solitons are also applied in particle physics, fluid mechanics, Bose-Einstein condensation and nonlinear optics [18–20]. Some researchers have studied solitons by solving the nonlinear evolution equations and analysing their soliton solutions [21–25]. As one of the classic nonlinear evolution equations, the nonlinear Schrödinger (NLS) equation can be solved to obtain soliton solution, and has been widely investigated by using different methods [26–32]. With the differential quadrature method, the dynamic problems constructed by the NLS equation have been analysed [26]. The existence and stability of the standing wave solutions for the NLS equation in n-dimensional space have been studied [27]. Using the generalized exponential rational function, a new method to solve the exact special solutions of the NLS equation has been proposed [28]. The unified method has been used to acquire optical soliton solutions of the NLS equation [29]. Moreover, the stability of full dimensional KAM tori for the NLS equation has been proved [30]. Local Cauchy theory for the NLS equation has been discussed [31], and nonlinear instability of half-solitons has been analysed [32]. However, the soliton transmission process can be simulated more accurately with the variable coefficient NLS (vcNLS) equation, when the transmission medium or boundary condition is not uniform [33–40]. For the vcNLS equation, dynamics of solitons have been explored [33], and soliton interactions have been discussed [34,35]. In addition, the breather-to-soliton transitions for the vcNLS equation have been found [36], and nonautonomous multipeak solitons have been obtained [37].

The goal of this study was to model the total leaf chlorophyll content (LCCtot) of Gannan navel orange leaves using a field imaging spectroscopy system in the visible and near-infrared domain. The spectral range from 400 to 1000 nm with 176 wavebands (a wavelength interval of 3.41 nm) or 360 wavebands (a wavelength interval of 1.67 nm), labeled as ‘‘Datasets_1.67’’ and ‘‘Datasets_3.41’’, respectively, were used. Although different spectral data types were used, better prediction results for LCCtot were based on Datasets_1.67 for LCCtot prediction. Several prediction models of LCCtot were built based on partial least squares regression (PLSR), artificial neural networks (ANN), ordinary least squares regression (OLSR), and stepwise linear regression (SLR) using full spectral and effective wavelength (EW) data (raw spectral (RS), first derivative spectral (FDS) and second derivative spectral (SDS) data). The determination coefficient (R2 ), the root mean square error (RMSE) and the residual predictive deviation (RPD) were used to evaluate the reliability and accuracy of the predicted LCCtot values. As a result, 14 (7 obtained from Datasets_1.67, 7 obtained from Datasets_3.41), 39 (21 obtained from Datasets_1.67, 18 obtained from Datasets_3.41) and 50 (27 obtained from Datasets_1.67, 23 obtained from Datasets_3.41) wavebands were selected from the RS data, FDS data and SDS data, respectively, as the EWs for LCCtot prediction of navel orange leaves. After that, PLSR and ANN predictive models were established using full spectra, and OLSR and SLR predictive models were built using the selected EWs. The experimental results demonstrated that these various regression methods were useful for estimating LCCtot in the order of PLSR models established using full spectra from RS data (F-RS-PLSR) > PLSR models established using full spectra from SDS data (F-SDS-PLSR) > PLSR models established using full spectra from FDS data (F-FDS-PLSR) > SLR models established using EWs by RS data (EWs-RS-SLR). However, models built with ANN and OLSR, where the RPD values were less than 3, cause the models to be inaccurate. Finally, in comparison, the F-RSPLSR model exhibited the best performance of LCCtot estimation; with the number of principal components (Pcs) = 5, this model provided high values of the R2 of calibration (C-R2 ) = 0.92 and the R2 of validation (V-R2 ) = 0.96, small values of the RMSE of calibration (C-RMSE)=0.05 mg/g and the RMSE of validation (V-RMSE) = 0.19 mg/g, and sufficient the RPD of calibration (C-RPD)=17.00 and the RPD of validation (V-RPD)=3.63 values. Overall, the best modeling method was PLSR. Hence, the PLSR applicability for assessing chlorophyll content in navel orange leaves was demonstrated.

Introduction

Chlorophyll is the main photosynthetic pigment present in green plants and plays an important role in controlling carbon exchange and plant productivity [1], [2]. The chlorophyll content increases in young expanding leaves, reaches the highest value at maturity, and then decreases significantly during senescence [3], [4]. Therefore, the chlorophyll content of plant leaves correlated with the nutritional status can theoretically be used as a marker of the growth status of plants. Measurements and estimates of chlorophyll content are regarded as a meaningful indicator of plant health, including nitrogen deficiency, water stress and certain diseases [2], which can provide theoretical guidance for crop nutrient diagnosis and field management. The traditional wet-chemical method for measuring chlorophyll is precise but costly, time-consuming and inapplicable to large-scale analysis. Hence, scientists have been developing convenient and rapid methods for the measurement of leaf chlorophyll utilizing its unique optical absorption feature. Extracting chlorophyll information from the spectral features of plants has become a major means of estimating chlorophyll contents because of its advantages of being fast, nondestructive and large-scale [1], [5]–[8]. Numerous studies have been conducted using spectral data to retrieve chlorophyll information as a function of time and space in environments such as the ground or airborne and spaceborne environments [9]–[16].

Abstract

Optofluidic biolasers are recently being considered in bioanalytical applications due to their advantages over the conventional biosensing methods Exploiting a photonic crystal slab with selectively dye-infiltrated air holes, we propose a new optofluidic heterostructure biolaser, with a power conversion efficiency of 25% and the spectral linewidth of 0.24 nm. Simulations show that in addition to these satisfactory lasing characteristics, the proposed lab-on-a-chip biolaser is highly sensitive to the minute biological changes that may occur in its cavity and can detect a single virus with a radius as small as 13 nm.

Nanophotonics merged with microfluidics− i.e., optofluidics− offers a new way of implementing miniaturized optoelectronic devicesthat can be intrinsically adaptive and reconfigurable. Unique properties of liquids, such asthe potential of integration in lab-on-a-chip systems and compatibility with microfluidic components make optofluidic systems highly competitive in the development of biophotonics. Moreover, most of the biochemical reactions should be reproduced in a fluid, making optofluidic system substantially advantageousin biological sensing applications. A novel emerging device in this area is the optofluidic biolaser that can measure changes in biological molecules precisely. When biochemical or biological molecules are incorporated into a gain medium a new class of laser known as the optofluidic biolaser can emerge [1]. A number of optofluidic biosensors based on different principles with diverse advantages, drawbacks, sensitivities, and detection limits, are developed in research and commercial products[2-7]. Among passive sensors, those based on photonic crystals(PhCs) [2-4] or ring resonators [7]show satisfactory sensing signal. However, other types of passive biosensors may experience weak sensing signal and broad spectrum [1].

Abstract

In this paper we demonstrate that micronised Egyptian blue pigment can be used as a safe and simple material to visualise latent fingerprints on non-porous surfaces as near-infrared luminescent impressions. This allows the detection of latent fingerprints on highly patterned and reflective surfaces that have proven challenging with existing techniques.

Introduction

The detection of latent fingerprints is extremely useful in forensic investigations to establish evidence of contact between the criminal, the victim, and/or the crime scene [1-3]. To that end, a wide range of chemical and physical methods have been developed to aid in their detection and recovery, the choice of which is dependent on the nature of the surface involved [1,2]. The most common approach to detecting latent fingerprints on non-porous items has been the use of dusting powders, which work through physical adhesion to the latent fingerprint deposit [1-5]. It has been estimated that in the United Kingdom, approximately 50% of the 60,000 fingerprint identifications per annum arise from powdered fingerprints [1]. Historically, a wide range of materials have been utilised as fingerprint powders; including carbon black, iron oxide-based magnetic powder and titanium dioxide; in attempts to achieve improved visualisation across a wide variety of surfaces and conditions [1-5]. In recent times, this has included attempts to use natural products such as turmeric as safe and inexpensive powders [6]. Several commercially available powders exhibit luminescence in the visible region of the electromagnetic spectrum, which to some extent can negate the interferences exhibited by highly patterned or coloured surfaces [1,2,4]. However, there remain many fluorescent, highly patterned and/or reflective surfaces that continue to prove troublesome [7-9].

ABSTRACT:

We developed nanosized, reduced graphene oxide (nano-rGO) sheets with high near-infrared (NIR) light absorbance and biocompatibility for potential photothermal therapy. The single-layered nano-rGO sheets were ∼20 nm in average lateral dimension, functionalized noncovalently by amphiphilic PEGylated polymer chains to render stability in biological solutions and exhibited 6-fold higher NIR absorption than nonreduced, covalently PEGylated nano-GO. Attaching a targeting peptide bearing the Arg-Gly-Asp (RGD) motif to nano-rGO afforded selective cellular uptake in U87MG cancer cells and highly effective photoablation of cells in vitro. In the absence of any NIR irradiation, nano-rGO exhibited little toxicity in vitro at concentrations well above the doses needed for photothermal heating. This work established nano-rGO as a novel photothermal agent due to its small size, high photothermal efficiency, and low cost as compared to other NIR photothermal agents including gold nanomaterials and carbon nanotubes.

INTRODUCTION:

Photothermal therapy employs photosensitizing agents taken up by cells to generate heat from light absorption, leading to photoablation of the cancer cells and subsequent cell death. To avoid nonspecific heating of healthy cells, photosensitizers must show high absorption in the near-infrared (NIR) and selective uptake in cancerous cells in tumors over normal cells in healthy tissues. Deep penetration and little nonspecific photothermal heating in the NIR window are due to the transparency and low absorption of light by tissues in this optical window. Materials currently under investigation with high optical absorbance in the NIR region for photothermal therapy include gold nanoshells, gold nanorods, gold pyramids, single-walled carbon nanotubes (SWNTs), and multiwalled carbon nanotubes.

Abstract

Polycrystalline CdTe films have been deposited onto glass substrates at 373 K by vacuum evaporation technique. The transmittance and reflectance have been measured at normal and near normal incidence, respectively, in the spectral range 200–2500 nm. The dependence of absorption coefficient, α on the photon energy have been determined. Analysis of the result showed that for CdTe films of different thicknesses, direct transition occurs with band gap energies in the range 1.45–1.52 eV. Refractive indices and extinction coefficients have been evaluated in the above spectral range. The XRD analysis confirmed that CdTe films are polycrystalline having hexagonal structure. The lattice parameters of thin films are almost matching with the JCPDS 82-0474 data for cadmium telluride. © 2002 Elsevier Science B.V. All rights reserved.

Introduction

Cadmium telluride is considered at present one of the most promising materials, for device applications. It has high absorption coefficient in the visible range of the solar spectrum and its band gap is close to the optimum value for efficient solar energy conversion [1,2]. The material can be prepared in n-type and p-type forms so that solar cells can be formed in both homojunction and heterojunction configurations. A survey of the literature shows that different techniques of deposition have been developed to obtain device grade CdTe thin films, among which electrodeposition [3], rf sputtering [4], closed vapor transport [5], spray pyrolysis [6], screen printing [7], and vacuum evaporation [8,9] are worth mentioning. All these techniques have their own merits and demerits in producing high quality CdTe films. Recently several workers have studied structural characteristic and optical properties depending on the deposition conditions [10–17]. Most of these investigations did not deal with each deposition condition, separately and some contradictions appeared in the results. Therefore in this work systematic investigation of the effect of the preparation conditions on the optical properties and structural characteristic has been carried out. An interpretation of the determined optical constant variations in correlation with the corresponding structural parameters is presented.

Baggage handling system (BHS) is a type of logistic system installed at airports, transporting passenger bags automatically from sources to destinations (e.g., from check-in counters to departure areas). The major functionalities of a BHS are baggage check-in, transportation, screening, tracking, sortation, earlystorage, etc., and are implemented by various logistical equipment (Yu and Xu, 2010). The carriers to transfer baggage can be conveyors, trays, carts, or their combinations within the system. Recent technological advancement in the BHS is destination-coded vehicle (DCV) where the speed of every bag can be controlled individually (Mao et al., 2015). A BHS is made up by a number of subsystems on the basis of baggage processing flow (van de Laar, 2009). A subsystem is normally comprised of machines that handle the baggage such as screening machines, loading robots, etc., and a number of buffers (e.g., queue conveyors) which are necessary during peak period. A BHS consists of a number of cascaded queueing systems which can potentially cause a bottlenecking problem within the system (de Neufville, 1994; de Neufville and Odoni, 2013).

Therefore, it can be advantageous if practitioners are able to verify the performance of subsystems via simulative analysis ahead of actual system deployment. Solution providers are usually requested to assess their design via simulation and present the performance results to the airport management when tendering a new BHS project. Hafizogullari et al. highlighted the importance of proactive system-level simulation in (Hafizogullari et al., 2003) with an example of Lambert St. Louis International Airport. A number of simulative studies are available in different aspects of the BHS, such as check-in area (Le et al., 2007), merge area (Johnstone et al., 2015), and especially screening area (Sterchi and Schwaninger, 2015; Dorton and Liu, 2016; Leone and Liu, 2005). Sterchi et al. investigated the effects of screening time and false alarm rate on the baggage throughput of airport security screening checkpoint in (Sterchi and Schwaninger, 2015). Reference (Dorton and Liu, 2016) verified the impacts of baggage volume and false alarm rate on the performance (waiting times and number of queues) by modelling the system using queueing theory. Leone et al. suggested a way to estimate the total number of explosives detection system (EDS) machines required and evaluated also waiting times and queue lengths using discrete-event simulation (Leone and Liu, 2005).

This paper concentrates on a different topic which is the routing strategy in airport baggage screening. Currently, according to the industry standard from Transportation Security Administration of the United State (Transportation Security Administration, 2011), baggage screening subsystems implement the round-robin (RR) and first-available (FA) policies for bag assignment. It is a very simple algorithm which distributes bags in a circular way without knowing anything about the system states. It can be easily implemented by software on a programmable logic controller (PLC) (Haneyah et al., 2013). The RR is the most common practice in the industry. It is the only load balancing policy for screening subsystems as stated in the official bidding document of CharlotteDouglas International Airport (Charlotte Douglas International Airport, 2014). In the design document (San Francisco International Airport, 2011; hereafter SFO, 2011) of San Francisco International Airport, the RR can be complemented with the FA. Under the FA scheme, bags are dispatched to the first screening line where the queue conveyors are not full. This strategy requires information from screening lines, and is only used when the queue utilization is extremely high. Both the RR and the FA fall into the category of static routing. The main disadvantage for static routing is the inability to handle variability. At the presence of unbalanced queue lengths (due to variability), neither RR nor FA can react quickly to improve the situation, because of the lack of feedback mechanism. This paper introduces a dynamic policy, namely joinshortest-queue (JSQ), to the airport screening process. It is not a new policy as it has been used in job scheduling in computing, communication theory, and so on (Mukhopadhyay and Mazumdar, 2016; Jiang et al., 2012; Iyengar et al., 2015). This approach relies on the real-time state feedback from queues and servers. A variety of literature demonstrated the optimality of the JSQ policy when the servers follow the first-come-first-serve (FCFS) principle (Winston, 1977; Nelson and Philips, 1993; Akgun et al., 2011).