We investigate the reverse saturable absorption (RSA) and optical limiting (OL) in a three-level V-type quantum system considering the effect of the spontaneously generated coherence (SGC). It is shown that in the absence of the SGC effect, the saturable absorption (SA) is dominant in the system. By taking into account the SGC effect, we prove that the SA dramatically switches to the RSA. Moreover, it is demonstrated that the OL threshold and OL efficiency can be controlled by the SGC effect. In addition, we show that the applied field properties such as detuning can modify the SGC-induced optical limiter efficiency. It is also shown an increase in the atomic density and length of the medium makes the optical limiter more efficient. The analytical calculation shows that the Kerr nonlinearity caused by the SGC effect is the main mechanism of the system evolution. Finally, the theoretical Z-scan experiment is presented to confirm the obtained results. Our proposed scheme can be useful to design controllable atomic optical limiters for optical devices with different sensitivities. Optical limiters are tools that can attenuate the transmission of light, and thus their presence in optical configurations is essential. When the intensity of the light entering the optical device exceeds a certain limit, which is defined as the optical threshold, the optical limiter enters into action and does not allow light to be emitted beyond this threshold. A wide range of materials in which optical limitation was inherently observed have always been traditionally used. These nonlinear materials mainly contain organic and inorganic materials7 such as quantum dots8, metal nanoclusters10 and carbon based materials14. Although Azzam et al. showed that the OL behavior depends on the density and concentration of the molecules in thin films15, generally the main characteristics of an optical limiter, including the OL threshold and OL range of materials that are inherently optical limiters, cannot be controlled. The design of comprehensive optical limiters with controllable features can be used to protect optical devices with different sensitivities. In recent years, Mahmoudi et al. have proposed an atomic optical limiter whose OL behavior characteristics can be controlled by coherent light intensity, as well as magnetic field16. In another work, this group presented a simple scheme in which they showed that the OL threshold and OL region in a three-level pump-probe V-type quantum system can be modified by a microwave field17.In recent decades, the advancement of technology has increased the need to use laser fields in both laboratory and industrial fields. This need has led to great attention to the development of innovations and ideas for the protection of optical elements against high-intensity lasers. The human eye and other optical and electronic devices and sensors may be damaged when exposed to high intensities of laser light. The development of optical phenomena relying on atomic coherence and quantum interference created by laser fields has led to the emergence of devices that have high controllability and efficiency. Optical limiting (OL)20 and nonlinear scattering23. When the RSA governs in a material, the absorption of the excited states is larger than the absorption of the ground state, leading to an increase in the absorption by increasing the intensity of the applied light. In contrast, absorption properties disappear gradually in the SA materials due to the depletion of the ground state.From a physical point of view, the two main mechanisms governing the generation of OL are based on the reverse saturable absorption (RSA)24. SGC is rooted in the interference between two spontaneous emissions of transitions from two close-lying levels to the common lower energy level with non-orthogonal dipoles in the quantum system. However, finding such conditions are difficult in real atomic system in free isotropic space25. It was suggested that the SGC can be generated in anisotropic vacuum, even for orthogonal dipole moment26. Several methods such as putting the atom inside a multilayer dielectric plate cavity27, coupling of upper two levels by applying a microwave field29, and applying the laser fields have been introduced to simulate the SGC30. Ficek and Swain proposed an alternative scheme that makes it possible to observe the effect of SGC on optical phenomena without considering the parallel dipole moments. In this scheme, the ground state is coupled to only one of the excited states with a laser field, and the two upper levels with perpendicular dipole moments are coupled together by applying a dc field. It was shown that the scheme is equivalent to the usual V-type three-level system with parallel dipole moments of transitions31.On the other hand, atomic coherence created by spontaneous emission is often referred to as vacuum induced coherence or spontaneously generated coherence (SGC) and has been widely studied in recent years. The effect of State superpositions created by spontaneous emission was introduced by Javanainen32. The effect of the SGC on the absorption spectrum has been experimentally investigated in a V-type33, Y-type and N-type atomic systems34. Various theoretical works have been done to determine the role of the SGC in the bistability and mulistability36, atom-photon entanglement38 in different atomic systems. Recently, it has been shown that SGC is capable of transferring the orbital angular momentum from a Laguerre–Gaussian field to a weak plane wave39. Moreover, Mahmoudi et.al showed that atoms can be cooled to even below recoil temperature under a cooling mechanism based on SGC-induced electromagnetically induced transparency40.In general, large intensities are necessary to modify the absorption properties of the medium, however, many nonlinear phenomena can be established in low intensities in the presence of quantum interference. In addition, quantum interference between different decays from upper levels can reduce the relaxation of the atomic coherence due to the spontaneous emission. These are the reasons why the role of SGC has been intensively investigated in various nonlinear phenomenaIn this paper, we take advantage of the coherence induced by SGC to introduce a simple controllable optical limiter. We consider a V-type three-level atomic system in the presence of the SGC to investigate the RSA and the corresponding OL behavior. By creating SGC and increasing its value, it is seen that the SA in the atomic system switches to the RSA, leading to an efficient OL. Moreover, it is shown that the OL threshold and OL ability to attenuate the transmission of light can be coherently modified in the presence of SGC. Our analytical solution shows that the physics governing the results is based on the Kerr nonlinearity due to the SGC. Ultimately, the SGC-induced OL is confirmed by the calculation of the theoretical Z-scan technique. Our suggested atomic scheme can be useful for designing optical limiters with controllable features to protect optical devices with different sensitivities.We introduce a three-level V-type quantum system in the presence of the SGC effect as has been shown in Fig. Here, entclass1pt{minimaWe are going to introduce the governing equations in theoretical issues of optical limiting. In an atomic medium, the polarization vector is given byl being as the thickness of the sample. As shown in Eq. (n (density of atoms) and tion Eq.  and usintion Eq.  that helentclass1pt{minimaThe normalized transmission of the probe field is considered as the ratio of output intensity to input intensity. It can be related to 41. So, the same experimental setup can be basically used to observe the role of SGC in the generation of OL. We introduce three important features for achieving proper optical limiter: (i) the limiting threshold , (ii) limiting amplitude (i.e. the minimum transmission during the region of power limiting effect) and (iii) initial transmission . Here, we present our results describing the transmission behavior of the system based on numerically solving the steady-state density matrix and field-propagation equations. Figure 42.In this section, before presenting the numerical results, it is desirable to point out some important considerations; we consider one possible realistic example to observe the phenomena using the entclass1pt{minimaAs shown in Fig. entclass1pt{minimaentclass1pt{minimaTo fully investigate the SGC effect on the optical limiting behavior, the probe field absorption is explained. Figure entclass1pt{minimaentclass1pt{minimaIn the following, we proceed to investigate the detuning effect of the probe laser field on the OL behavior. Figure Now, we are going to introduce resonance absorption for achieving better efficiency of an optical limiter. The resonance absorption, To interpret the physical concept of the phenomenon, we are going to describe the transition paths related to the various terms in the numerator of the Eq. . Figure s of Eq.  is shownmentclass2pt{minimHere, in order to infer the physical concepts for OL behavior, we proceed to investigate the population distribution. The taken parameters are the same as Figs. z position. So, when the sample is moved along the z-direction (Now, we are interested in introducing a Z-scan technique to analyze the features of optical limiting behavior. The open aperture Z-scan configuration is formed from a laser, thin lens, diaphragm, and detector. In this configuration, a Gaussian laser beam propagating in the z-direction can be focused by using the lens. Notice that transmission is considered as a function of the mentclasspt{minimaWe investigated the RSA and OL behavior in a three-level V-type quantum system considering the SGC effect. It was shown that when the SGC effect is ignored, the SA is the dominant phenomenon in the system. By applying the SGC effect, it is demonstrated that the SA switches to the RSA. In the RSA region, we showed that the transmission of the probe field attenuates dramatically by increasing the SGC effect, which leads the optical limiter more efficient. Moreover, it is illustrated that the OL threshold and OL region as the major characteristics of the optical limiter can be controlled by the SGC effect. It was also shown that the applied field properties such as detuning can modify the optical limiter efficiency. The analytical results determined that the Kerr nonlinearity generated by the SGC effect is the main mechanism in the system evolution. Moreover, it is shown that the SA is dominant in one-photon resonance condition. In addition, it was depicted that an increase in the atomic density and length of the medium makes the optical limiter more efficient. Ultimately, the theoretical Z-scan experiment was presented to confirm the validity of the obtained results. The proposed scheme can be used to design controllable atomic optical limiters for optical devices with different sensitivities.


The practice of green consumption has become a common initiative of the international community. Existing studies have shown that emotional factors have an important impact on consumer behavior, but few scholars in the field of green consumption behavior have explored the relationship between positive emotions and green purchase behavior in specific dimensions. This study creatively put forward two dimensions and four kinds of positive emotional appeals which include the cherishing appeal, the yearning appeal, the proud appeal, and the admiring appeal. Through the conceptual model analysis based on the data, the effects of different four positive emotional appeals on consumers’ perceived green value, perceived green responsibility, and green purchase behaviors were confirmed. The results indicated that the four kinds of positive emotional appeals, perceived green value, perceived green responsibility, and green purchase behavior were positively correlated. Perceived green responsibility and perceived green value have significant mediating effect on the relationship between positive emotional appeals and green purchase behaviors. Middle doctrine significantly moderates the relationship between positive emotional appeals (Cherishing VS. Yearning) and perceived green value. Nowadays, the global natural ecological environment is deteriorating day by day, and a series of pollution problems emerge one after another. Therefore, it is imperative to attach importance to and actively advocate green consumption behavior. The 19th national congress of the communist party of China (CPC) once again stressed the necessity to establish and practice the concept that clear waters and green mountains are valuable assets. However, in general, residents’ green purchase intention and behaviors are not popular, and people are not willing to pay a premium for the green properties of products. The government and society have made great efforts to promote environmental protection and green consumption, but the effect is not satisfactory. The report of the International Institute of Green Finance of the Central University of Finance and Economics pointed out that the green penetration rate of consumers of different age groups in China is quite different and the environmental protection concept is quite different among different age groups. Consumers of some age groups do not yet have a good awareness of green consumption.According to the research results of scholars, the influence of different emotions on consumers’ purchase behavior is quite different. Scholars often use the emotion dichotomy, which divides emotion into negative and positive dimensions according to the experience structure . PositivCherish refers to the psychological activity of consciously cherishing the objective things, others, and themselves. The awareness of cherishing is relatively stable after it is formed in an individual and will not fade or even disappear due to changes in the environment. It will not go away, but it will change. Once the cherishing consciousness is formed, it will continue to strengthen under the influence of positive conditions; on the contrary, it will gradually weaken under the influence of negative conditions. Yearning refers to the desire to get or to achieve because of love or envy of a certain thing or state, and it is the “expected prospect” of people. Yearning is accompanied by people’s good wishes and positive goals, which can inspire people to be full of motivation to move forward and can make people focus on the goals they want to achieve and focus on those goals. Yearning can motivate people to develop in a good direction. It will form a beautiful picture in people’s imagination, and it will keep appearing in their minds. People can form the hint of continuous self-motivation by imagining the achievement of goals, motivating individuals to make continuous efforts toward the vision of their dreams. That is, yearning helps arouse people’s imaginations and expectations, which motivate individuals to take action to achieve their goals. When yearning enters the expectation into the subconscious, this kind of vision for the future will become the unswerving “belief” of the individual. Under the guidance of the belief, the individual will work hard toward the desired prospect. People who are full of yearning focus on the future and hope to achieve the desired state through present and future efforts.Proud is a positive emotion that includes a sense of accomplishment and self-satisfaction  and is aAdmiring means approval and appreciation, which refers to an individual’s positive emotional attitude toward others and this emotion also promotes oneself . It is aIn the field of green marketing research, there are two gaps in current research: (i) lack of research specifically on emotional appeal; (ii) lack of research on the impact of different dimensions of positive emotional appeal on consumers’ green consumption behavior. Investigating the role of positive emotions in different dimensions can help companies conduct green marketing more effectively. Therefore, this paper focuses on the differences and effects of the four representative dimensions of positive emotional appeals on consumers’ green purchasing behavior . The former includes the cherishing and yearning appeal, which, respectively, represent the appreciation of the present beautiful environment and the expectation of the future beautiful environment. The latter includes the proud and admiring appeal, which, respectively, represent the pride in one’s own appropriate environmental behavior and the appreciation of others’ appropriate environmental behaviors.We believe that consumers will choose different reference points when stimulated by different types of emotional appeals. Yearning appeals make consumers focus on the future and therefore use the future situation as a reference point. The cherishing appeal emphasizes the protection of the existing environment, so the current state is set as a reference point. Admiring appeal will make consumers pay more attention to the green consumption behavior of others, that is, they will set the green consumption behavior of others as the reference point. On the contrary, proud appeal will make consumers pay more attention to themselves, so they tend to set their own behavior as a reference point. Due to the difference in the selection of reference points, it will further affect the perception of consumers. Therefore, based on the above discussion, this article will use prospect theory to explain consumer perception differences.This paper will first discuss the difference in the effects of cherishing appeal and yearning appeal on consumers’ green purchasing behavior and the mechanism, both of which belong to the dimension of emotions toward a better environment. We suggest that yearning appeal has a greater positive impact on consumers’ green consumption behavior than cherishing appeal and the relationship between the effects is mediated by perceived green value. There are several reasons as follows:Firstly, under different positive emotional appeals, consumers make different responses. According to the broaden-and-build theory of positive emotions, positive emotions have the role in expanding people’s thoughts and actions, having a relatively lasting influence on individuals . The expSecondly, both the cherishing appeal and the yearning appeal reflect the concern for the environment. This will lead consumers to associate the purchase of green products with protecting the environment. Consumers will consider the value of purchasing green products to the environment, that is, pay attention to the green value of products. This paper will use reference points to explain the difference in the impact of cherishing appeal and yearning appeals on consumers. Yearning appeal will make consumers pay more attention to the beautiful ecological environment in the future, which will set the beautiful ecological environment in the future as a reference point. After purchasing green products or conducting green consumption, will bring the existing environmental conditions closer to the desired environmental conditions. According to prospect theory, a “reference point” divides the space of outcomes into regions of gain and loss . OutcomeIn addition, it is worth noting that the previous behavior of consumers determines the current ecological environment. Under the condition of cherishing appeal, no matter whether consumers are satisfied or dissatisfied with the current ecological environment, green purchasing behavior can only maintain the status quo. Therefore, cherishing appeals brings less perceived green value.Thirdly, perceived green value refers to individual’s subjective evaluation for the effectiveness of green products or green consumption. In summary, compared with cherishing appeals, yearning appeals have a more positive effects on consumers’ green purchasing behavior. This is mediated by perceived green values. Yearning appeals can lead to higher perceived green values, due to the choice of reference points and the intensity of emotion. Perceived green value can have a significant effect on green purchase behavior. Cherishing appeals and yearning appeals may also make consumers consider their own green responsibilities. Cherish the appeal makes consumers pay attention to their responsibility to maintain the existing environment and yearning for the appeal makes consumers pay attention to their responsibility to improve the environment. Although the two are different, we believe that the difference in intensity is not significant. Therefore, we suggest the relationship between emotions toward a better environment appeals  and green purchase behavior is not mediated by consumers’ perceived green responsibility.Hence, we propose the following:H1: Compared with the cherishing appeal, yearning appeal has more positive effects on the consumers’ green purchase behavior.H2: The relationship between emotions toward a better environment appeals  green purchase behavior is significantly mediated by consumers’ perceived green value.Next, this paper will discuss the differences in the effects of proud appeal and admiring appeal on consumers’ green purchasing behaviors and their mechanisms, both of which belong to the dimension of emotion toward the appropriate individual environmental behavior. We suggest that compared with proud appeal, admiring appeal has a greater positive effect on consumers’ green consumption behavior, and the relationship between them is mediated by perceived green responsibility. The reasons are as follows:Firstly, as far as the positive emotions for the individual’s environmentally appropriate behavior are concerned, compared with self-recognition or self-satisfaction, recognition, and appreciation from others are more effective in motivating individuals to practice proper behaviors. The view of social cognitive theory is that people tend to be more inclined to learn from people or their behaviors they admire . People Secondly, we also use reference points to explain the differences in the impact of proud appeal and admiring appeal on consumers’ green buying behavior. Admiring appeal will make consumers pay more attention to the green consumption behavior of others, that is, they will set the green consumption behavior of others as the reference point and compare their own purchasing behavior with the green purchasing behavior of others. According to prospect theory, outcomes above the reference point are evaluated as gains and outcomes below the reference point are evaluated as losses. When the behavior of others is set as the reference point, the individual’s own behavior is on the left side of the reference point and purchasing green products means reducing “losses.” In other words, close the gap with others by purchasing green products. On the contrary, proud appeal will make consumers pay more attention to themselves, that is, set their own behavior as a reference point, and the result of further green purchasing behavior at this time means “gains.” In other words, buying green products means improving oneself and gaining more sense of achievement. According to the loss aversion effect, individuals are more reluctant to accept “losses” than “gains.” Therefore, compared with the proud appeal, the admiring appeal has a stronger positive impact on consumers’ green product purchase behavior. Besides, for the same reason as the first point, under the stimulation of admiring appeals, consumers will be aware of the good green purchasing behaviors of others in society, which further enhances consumers’ perceived green responsibility.Thirdly, In summary, compared with the proud appeal, the admiring appeal has a more positive impact on the green purchasing behavior of consumers. This is mediated by perceived green responsibility. Admiring appeals can lead to higher perceived green responsibility and perceived green responsibility can have a significant impact on green purchasing behavior. Moreover, stimulated by proud appeals or admiring appeals, consumers pay more attention to the sense of achievement brought by purchasing green products or narrowing the gap with others rather than the green value of green products. Therefore, we suggest that the relationship between emotions toward the appropriate individual environmental behavior appeals  and green purchase behavior is not mediated by consumers’ perceived green value. Hence, we propose the following:H3: Compared with the proud appeal, admiring appeal has more positive effects on the consumers’ green purchase behavior.H4: The relationship between emotions toward the appropriate individual environmental behavior appeals  and green purchase behavior is significantly mediated by consumers’ perceived green responsibility.Consumers’ psychological factors and situational factors exert a great impact on the green purchase behavior. Among multiple situational factors, individual values occupy an important position. H5a: The middle doctrine negatively moderates the influence of positive emotional appeals (cherishing vs. yearning) on perceived green value.H5b: The middle doctrine negatively moderates the influence of positive emotional appeals (cherishing vs. yearning) on green purchase behavior.H5c: The middle doctrine negatively moderates the influence of positive emotional appeals (proud vs. admiring) on perceived green responsibility.H5d: The middle doctrine negatively moderates the influence of positive emotional appeals (proud vs. admiring) on green purchase behavior.Based on the broaden-and-build model of positive emotion theory and prospect theory, this study deeply explores the relationship and mechanism between the positive emotional appeals and green purchase behavior, focusing on comparing differences in stimuli effects of different types of positive emotions, at the same time investigating the moderating role of middle doctrine.The conceptual model of this study is shown in Energy-saving refrigerators and air conditioners are often used as products in previous green consumption experiment because of their green environmental properties. After searching in various ways, this study chose a relatively novel green product—green power certificate, which can fully reflect the consumer’s sense of responsibility, as the experimental product. The green certificate is an electronic certificate for the green electricity produced by power generation enterprises with a unique code identification. Governments, enterprises, and individuals all can subscribe for green certificate on the information platform. On the one hand, the green certificate trading system can guide and regulate the priority consumption of renewable energy power, effectively improve the consumption of green power, reduce the speed of thermal power generation, and promote the efficient use of renewable energy, which is of great significance to the governance of environmental pollution. On the other hand, China’s renewable energy subsidy cumulative gap is large and unsustainable, so the introduction of green certificate system can establish a long-term mechanism for the development of renewable energy. To sum up, now that subscribing the green certificate is a kind of green purchase behavior, regarding the green certificate as an experimental product in this study is scientific and feasible.In this study, four self-made videos (picture + text + voice + background music) were used as stimulation materials, which had a stronger sense of substitution than simple text description and enabled the respondents to have a deeper understanding of the experimental materials in a more vivid and accurate form. Each video has a short paragraph of text in front of the simple and popular introduction of green certificate, and then follow closely to reflect the corresponding feelings of green video.By reviewing the existing relevant literature and drawing on the research experience of relevant scholars, this paper summarizes the measurement items of consumers’ perceived green value, perceived green responsibility, green purchase behavior, emotional arousal, and middle doctrine in this study. Likert seven-point scale was used to measure all the items in the questionnaire. The specific measurement items of each variable are shown in In this study, the positive emotional appeal videos and the measurement questionnaire were edited into four online links and randomly distributed to the respondents through the Internet. The experiment was conducted through respondents watching the video and filling the corresponding questionnaire, the period of which is August to September 2018. After eliminating the invalid questionnaires, a total of 433 valid questionnaires were collected in this experiment and the sample effective rate was 89.2%. In these 433 valid questionnaires, 48.3% were male, and 51.7% were female. Age distribution is generally below 44 years old, accounting for 97.2% of the total sample size. Education is mainly concentrated in the undergraduate degree and above, because they were more capable of understanding the study and more willing to participate in the experiments.First, we test the manipulation of four emotional awakening videos. The respondents watched four emotional awakening videos, and then, they fill in the first four questions of the questionnaire. We test the validity of video by the scores of the items . The items include as: (1) After watching video, I will cherish the beautiful ecological environment more. (2) After watching video, I will be more yearning for a better ecological environment in the future. (3) If I subscribe to the green power certificate, I will be proud of my behavior. (4) If someone else subscribes to the green power certificate, I will admire his behavior.Single factor analysis of variance by 433 samples data, we found that the average score of the cherishing appeal in item (1) was significantly higher than that of other emotions, the average score of the yearning appeal in item (2) was significantly higher than that of other emotions, the average score of the proud appeal in item (3) was significantly higher than that of other emotions, the average score of the admiring appeal mean in item (4) was significantly higher than that of other emotions. This indicates that the experiment of different positive emotional appeals in this study was successfully manipulated.In this paper, the internal reliability index was used to measure the reliability of the scale. As shown in Confirmatory factor analysis was performed using AMOS 24.0 and the results were as follows: absolute fit indices The output of AMOS24.0 shows that the standardized factor loadings of each measurement item on its corresponding latent variable are between 0.89 and 0.97. As shown in label 2 the average variance extracted (AVE) of each latent variable was greater than 0.5 and the composite reliability (CR) was greater than 0.8. The above results indicated that the scale of this study has good convergent validity.As shown in Common method bias: since the measurement of constructs in this paper uses scales, there may be a problem of common method bias. This study adopted a series of control procedures to reduce the interference caused by common method bias, such as emphasizing the anonymity of this study and improving the items and order of the scale. In this paper, controlling for the effects of an unmeasured latent methods factor (ULMC) was used to test whether there was a common method bias in the study. We build two models by using AMOS 24.0. The model with both method and substantive components could be compared to an identical model except with construct correlations constrained to the values obtained in the substantive-only model. If the two models are significantly different, there is evidence of method bias . The comAccording to the results of correlation test, consumers’ perceived green value, perceived green responsibility, green purchase behavior, and middle doctrine were highly correlated at the test level of 0.01. Under four different types of positive emotional appeals, the mean comparison of different positive emotions is displayed in figure. As can be seen in figure, compared with the other three emotions, the yearning appeal leads to the highest degree of perceived green value, perceived green responsibility, and green purchase behavior.Then we classified four kinds of positive emotional appeals into two specific dimensions, and conducted independent sample T test in different groups, the results of which are shown in table. It can be seen from In order to further test the mediating effect of perceived green value and perceived green responsibility, we adopted the Bootstrap method proposed by As for the cherishing-yearning group, according to By analyzing the proud-admiring group in the same way, it can be found that the mediating effect of perceived green value is not significant, while the mediating effect of perceived green responsibility is significant. In the absence of mediating variables, the confidence interval of the direct effect of positive emotional appeal on green purchase behavior does not include 0, indicating that the direct effect is significant, which proves that perceived green responsibility plays a partial mediating role in the path of positive emotional appeal affecting green purchase behavior.In conclusion, H2 and H4 is proved to be true.In this section, we test the moderating effect of the middle doctrine on “positive emotional appeals-perceived green value,” “positive emotional appeals-perceived green responsibility,” and “positive emotional appeals-green purchase behavior.” Since the theoretical model of this study is a moderated mediation model, we adopt PROCESS 3.3 of Hayes and select model 8 for analysis. In group 1, the results are displayed in The aim of this study was to explore the influence effect and mechanism of positive emotional appeals on green purchase behavior, enriching the research of positive emotions on green purchase behavior. At present, scholars’ studies have gradually shifted from the cognitive to the emotional level to seek the influencing factors of green purchase behavior; nevertheless, most of which are lack of relevant empirical studies. Based on the results of previous qualitative research and the direction of national policies, it is the first time that creatively introduces the two specific positive emotions into study, including the cherishing and the yearning. At the same time, combined with the Chinese traditional cultural background, this paper incorporated middle doctrine into this theoretical model as a moderating variable, which is helpful to promote the localization of positive emotion and green purchase behavior in the field of consumer behavior.In this study, we discovered that the diverse types of positive emotional appeals exerted different influence on consumers’ perceived green value, perceived green responsibility, and green purchase behavior. Compared with the cherishing appeal, the yearning appeal is more effective in promoting the perceived green value and green purchase behavior. Compared with the proud appeal, the admiring appeal is more effective in promoting the perceived green responsibility and green purchase behavior. This conclusion confirms We found that under the state of positive emotion, perceived green value has significant mediating effect on the relationship between positive emotional appeals (cherishing vs. yearning) and green purchase behaviors. This is consistent with the research conclusions of Finally, middle doctrine significantly negatively moderates the relationship between positive emotional appeals (cherishing vs. yearning) and perceived green value but no evidence was found to support the moderating effect of middle doctrine on the other paths . That is, for consumers with different degrees of middle doctrine, admiring appeal  has a stronger impact on the perceived green responsibility and green purchasing behavior. Our explanation for this result is that consumers with strong moderate values hold such a view that the existence of the individual depends on the relationship of the whole and at the same time has an impact on the whole, so the behavior of others has a stronger impact on them. Furthermore, admiring appeal makes consumers with a higher degree of moderate values pay attention to the green buying behavior of others. Therefore, for consumers with a higher degree of moderate values, the effect of admiring appeal is also higher than that of proud appeal.This research makes three main theoretical contributions: First, our study revealed the different effects of the four dimensions of positive emotional appeal on consumers’ green purchase behavior. Existing research on emotional appeal mainly focuses on the difference in the impact of rational appeal and emotional appeal , but theSecond, this research advances understanding of how four dimensions of positive emotional appeals shape consumers’ green purchasing behavior. This study verified that cherishing appeal and yearning appeal lead to differences in consumers’ perceived green value, which further affects their green purchase behavior. Positive emotional appeals affect consumers’ perceived value, which is a brand-new point of view. This study also proved that proud appeal and admiring appeal have different effects on consumers’ perceived green responsibility and further influence consumers’ green purchase behavior. The above viewpoints and conclusions provide a new perspective, which is helpful to understand the impact of positive emotional appeals on consumers’ green consumption behavior. At the same time, this paper incorporated middle doctrine into this theoretical model as a moderating variable, which is helpful to promote the localization of positive emotion and green purchase behavior in the field of consumer behavior.Third, this study expanded the scope of application of the Broaden-and-Build Theory of positive emotions and prospect theory. For the first time, we use prospect theory to explain that consumers’ perceived differences in green value and green responsibility are due to the selection of different reference points (present or future and self or others) under different emotional appeal stimuli. This provides a new perspective for other researchers trying to understand the impact of emotional appeal.The research conclusion provides valuable marketing inspiration and policy management experience for both enterprise managers and government policymakers. Firstly, make full advantage of positive emotional appeal to guide consumers to green purchase sustainably. For enterprise, in the process of promoting the products, it is of great significance to add positive emotional attributes to capture the consumer’s inner demand and arouse their inner resonance, guiding them to buy. At the same time, the government is supposed to attach prime importance to cultivating and enhancing positive emotional attainments and strengthen their recognition of ecological and environmental behaviors, so as to encourage individuals strive for a green ecological environment and actively participate in the sustainable green purchase. Secondly, the cherishing and admiring appeals should be fully valued. To be specific, enterprises can incorporate beautiful ecological environment pictures or videos into the advertisements. In addition, short films, stories, or music can be broadcast to publicize individuals’ green purchase behavior, in order to infect more individuals to join the team for affirming and appreciating others’ environmental protection behavior. Finally, emphasize the role of green responsibility to enhance consumers’ inner awareness of ecological environmental protection. When making product marketing plans, enterprises should not only comprehensively introduce the unique performance of products, but also integrate some elements which can awaken consumers’ awareness of ecological responsibility, urging consumers to be willing to purchase green products.This work suggests several interesting opportunities for future research. One is to investigate the long-term effects of different types of emotional appeals on consumers’ green purchasing behavior. Our experimental study confirms that emotional appeals have an impact on consumers’ single green purchase behavior but does not take into account consumers’ long-term green purchase behavior. So, researchers can use the Real-time Longitudinal Methods to investigate whether consumers’ behaviors in a certain period of time have continuity and whether its green buying behavior increases or decreases over time. Another opportunity for further research is to more deeply explore the role of positive emotional appeals. For instance, future research can be conducted on the effect of a combination of different positive emotional appeals on consumers  and the effects of other types of affective appeals on consumers.The original contributions presented in the study are included in the article/JianmW: conceptualization, data curation, and writing-original draft preparation. ZH: methodology and supervision. JiangW: methodology and software. JB: visualization and investigation. JG: methodology and investigation. XY: conceptualization, methodology, software, and manuscript revision. All authors contributed to the article and approved the submitted version.This study is supported by Major Project of the National Social Science Fund of China (20ZDA087).The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


UAVs are sensor platforms increasingly used in precision agriculture, especially for crop and environmental monitoring using photogrammetry. In this work, light drone flights were performed on three consecutive days (with different weather conditions) on an experimental agricultural field to evaluate the photogrammetric performances due to colour calibration. Thirty random reconstructions from the three days and six different areas of the field were performed. The results showed that calibrated orthophotos appeared greener and brighter than the uncalibrated ones, better representing the actual colours of the scene. Parameter reporting errors were always lower in the calibrated reconstructions and the other quantitative parameters were always lower in the non-calibrated ones, in particular, significant differences were observed in the percentage of camera stations on the total number of images and the reprojection error. The results obtained showed that it is possible to obtain better orthophotos, by means of a calibration algorithm, to rectify the atmospheric conditions that affect the image obtained. This proposed colour calibration protocol could be useful when integrated into robotic platforms and sensors for the exploration and monitoring of different environments. For many years, mapping crops through remote or proximal sensing using unmanned aerial or ground vehicles (UAV or UGV) represents a crucial technology used in Precision Agriculture and Smart Farming . Indeed,Typically, UAVs in precision agriculture are used for outdoor environments   where GlIn detail, orthophotos represent high-precision data collection for both precision agriculture and forest management based on orthogonal projections. To obtain an orthophoto, one must have an image, usually a Digital Surface Model (DSM) .After the flight is performed by drones or other carriers, it is important to verify how the orthophoto is generated. In fact, aerial images obtained by UAVs can be affected by several factors  that can lead to image deformation with regard to pixels . MoreoveAs reported by Wierzbicki et al. , meteoroGenerally, orthophotos obtained by a UAV under various atmospheric and illumination conditions have a number of defects. These defects arise directly from the acquisition method and have an impact on the quality of the photogrammetric product. In the work by Burdziakowski et al. , the useTo overcome this problem, and thus improve the quality of orthophotos, innovative photogrammetric techniques are being developed . One metColorimetric calibration prior to photo/image interpretation is gaining increasing attention worldwide in many diverse disciplines such as biology since the colour is both a phenetic characteristic of organisms and a feature of the environmental space occupied by organisms ,17; howeIn this regard, the purpose of this work is to verify the advantages of an innovative colour calibration algorithm for UAV images used for orthophoto reconstruction under different environmental conditions. This work represents a breakthrough because, although colorimetric calibration can help in orthophoto reconstruction in the presence of different lighting and weather conditions, currently no studies on this topic have been found in the present literature.On three consecutive days (14–16 January 2020), several flights (18) with a UAV DJI Spark  were conducted on an experimental agricultural field of around 2.5 hectares located in Monterotondo Scalo . The surface is composed of a plain field set aside. The field was divided into six zones . For all six zones, the UAV compass was heading 129° SE. The images were acquired with uneven light during the three days of flying, under the influence of weather conditions and sun position during the day. The total flight time (including take-off and landing) was around 12 min.The UAV digital camera (DJI Spark—model FC1102) collected still images every 3.34 s using a shutter speed of 1/533 s and sensor sensitivity of ISO 100. The camera specifications are described in At the beginning of each flight, an image colour checker GretagMacbeth (24 patches)  was acquired for the colour calibration. This image serves for the posteriori colour calibration. The a priori knowledge of the colour checker patches values allowed the colour calibration of all the images following the thin-plate spline interpolation function  in the RAfter image acquisition, the orthophotos were reconstructed using the software “Agisoft Metashape Professional version 1.6.6″ according to the following steps: project creation; identification of the same region (bounding box) and align photo with GPS information inside the image; settings of GCP (Ground Control Points), optimising the camera alignment without GPS inside the image and with GCP; build a dense cloud, build mesh, build texture, build tiled model, and build orthomosaic. The final step consists of exporting the orthophoto in tiff files with LZW compression.A comparison between the orthophotos obtained with calibrated and non-calibrated images was conducted. Five Ground Control Points have been used to reconstruct the orthophoto, and the other four  were used to check the quality of the reconstruction. The GCP and checkpoint are always the same for all the calibrated and non-calibrated reconstructions to avoid influences on the results.A total of 30 orthophotos were obtained: 15 from calibrated images and 15 from non-calibrated images; among which, 3 were from the reconstruction of the zones of each day and 12 randomly combined the six zones over the three days of the experiment. The combination of the zones was the same between calibrated and non-calibrated orthophoto reconstructions.A series of parameters were obtained after orthophoto reconstruction: Number of images used for the reconstruction, Number of tie points, Number of projections, Reprojection error, Control points Total Root Mean Square Error (RMSE), and Check points Total RMSE.Percentage Camera stations/Nimg: represents the percentage of images used for the reconstruction with respect to the total number of images available; this parameter indicates how many “good” images serve for the reconstruction.A tie point is a point in a digital image or aerial photograph that represents the same location in an adjacent image or aerial photograph; the larger the number of tie points, the more accurate the reconstruction.The number of projections represents the total number of projections projected from all overlapping images to compute and construct all the matched points. The number of projections is correlated to the number of points successfully matched .The reprojection error is a geometric error corresponding to the image distance between a projected point and a measured one. It is used to quantify how closely an estimate of a 3D point recreates the point’s true projection.Control points Total RMSE represents the total error of the five GCP positioning.Check points Total RMSE represents the total error of the four checkpoints positioning.To make the spatial quantitative comparison between orthophotos, photos were superimposed using the nine ground control points (landmarks) on each of the 30 images. A consensus configuration  was calculated . The sofAfter the orthophoto superimposition, the central part of the agricultural C field wp < 0.05) differences in the percentage of camera stations on the total number of images and the Reprojection error.Differences between the parameters obtained after orthophoto reconstruction from calibrated and non-calibrated reconstructions are reported in p < 0.0001) between the calibrated and non-calibrated images , significant results can be obtained for some parameters used in orthophoto reconstruction  but also for other parameters used, even if they do not report significant results, which are still advantageous to the orthophotos from calibrated images. By increasing the number of images, and thus reconstructions, significant differences can be achieved. Therefore, this work contributes to improving the repeatability of drones’ survey image acquisition, allowing a more homogeneous and quantitatively valid orthophoto reconstruction using calibrated images. This allows for the reduction or the elimination of defects due to different lightning conditions through reconstruction and calibration.p < 0.0001) difference between medians .The comparison of the calibrated and non-calibrated orthophotos through a Wilcoxon paired test on the 300 RMS SD of the three R, G, and B channels show a highly significant . As a result, the noise due to the variability of the illumination conditions does not average to zero and cannot be reabsorbed into an illumination offset. Therefore, it is crucial to use a proper calibration method for a proper reconstruction. This colorimetric calibration was shown to be a potential tool to contain or eliminate the problems arising during the orthophotos’ reconstruction. Often, a flight performed during a precise phenological plant stage or, for example, during a pathogen attack which is crucial for an agrochemical intervention, is not repeatable. This tool could aid orthophoto use even when some problems arise during flight, lowering the final errors. The number of reconstructions used in the present work was low, however, from a future perspective, increasing their number would have a greater meaning and therefore a stronger calibration could be obtained along with the derived benefits. In conclusion, the results obtained can boost the performances of UAVs through the application of an innovative calibration algorithm. Moreover, the technique, producing more stable and standardised images in terms of light and colour, can broaden the environmental condition in which it is possible to fly, thus increasing the surveying potential of valid precision agriculture tools.


The purpose of image dehazing is to remove the interference from weather factors in degraded images and enhance the clarity and color saturation of images to maximize the restoration of useful features. Single image dehazing is one of the most important tasks in the field of image restoration. In recent years, due to the progress of deep learning, single image dehazing has made great progress. With the success of Transformer in advanced computer vision tasks, some research studies also began to apply Transformer to image dehazing tasks and obtained surprising results. However, both the deconvolution-neural-network-based dehazing algorithm and Transformer based dehazing algorithm magnify their advantages and disadvantages separately. Therefore, this paper proposes a novel Transformer–Convolution fusion dehazing network (TCFDN), which uses Transformer’s global modeling ability and convolutional neural network’s local modeling ability to improve the dehazing ability. In the Transformer–Convolution fusion dehazing network, the classic self-encoder structure is used. This paper proposes a Transformer–Convolution hybrid layer, which uses an adaptive fusion strategy to make full use of the Swin-Transformer and convolutional neural network to extract and reconstruct image features. On the basis of previous research, this layer further improves the ability of the network to remove haze. A series of contrast experiments and ablation experiments not only proved that the Transformer–Convolution fusion dehazing network proposed in this paper exceeded the more advanced dehazing algorithm, but also provided solid and powerful evidence for the basic theory on which it depends. In many practical applications of computer vision, image restoration  plays anHaze is a traditional atmospheric phenomenon . In hazyThe influence of haze on image quality results in a series of problems. In the field of ground photography, because light penetrating dense atmosphere is necessary for shooting distant objects, haze causes inaccurate estimates. In the same way, haze has a significant impact on some advanced computer vision tasks. Many advanced computer vision tasks require images with clear visibility as input; however, degraded images taken in hazy weather often cannot meet the requirements. This has the most serious impact on outdoor target recognition systems, outdoor automatic monitoring systems and intelligent driving vehicles. Therefore, in order to meet the requirements of high-level computer vision tasks, it is necessary to design an effective dehazing algorithm to restore the original colors and details to images with visibility degradation.In recent years, with the development of deep learning  and the Image dehazing methods can be divided into four categories according to their inputs: (1) multiple image dehazing, (2) dehazing based on polarization filter, (3) image dehazing using additional information (such as depth or geometric information), and (4) single image dehazing .The dehazing method based on multiple images solves the dehazing issue by obtaining the changing atmospheric state from multiple images. In other words, it needs to wait until the atmospheric state or haze concentration changes. Therefore, this method is impractical for applications in the real world. Dehazing based on a polarization filter eliminates the need for real atmospheric state change. In this method, different filters are applied to different images to simulate changing weather conditions. However, only static scenes are considered when using the polarization-filtering-based haze removal method. Therefore, this method is still not suitable for real-time dynamic scenes. In order to solve the shortcomings of these methods, some researches have proposed dehazing techniques that use only the depth information or estimated scene 3D model information of a single image. However, it is usually very difficult to obtain additional information about the single image .Our research mainly focuses on single image dehazing methods.There are two main methods to remove haze from a single image, i.e., the methods based on prior information ,10,11,12The contributions of this paper are as follows:(1) A novel Transformer–Convolution hybrid layer is proposed, which aims to improve the dehazing ability of the network by using the global modeling characteristics of Transformer and the local modeling characteristics of convolution.(2) The adaptive fusion mechanism is used to perform a learnable fusion of the output results of the Swin-Transformer and optional convolutional blocks.(3) Compared with the simple residual blocks, we use two different convolutional blocks that are more suitable for image dehazing tasks to improve the ability of the network to extract and reconstruct features at different stages.The method based on prior information mainly estimates the medium transmittance and atmospheric light intensity to describe the formation of haze by using some statistics of haze images. The final clear image is obtained by solving the atmospheric scattering model. This kind of method was widely used in the research of early image dehazing. Fattal ,9 realizHe et al. proposed a dark channel prior (DCP) . This meUnlike the use of local prior information, Berman and Avidan proposed a non-local color prior (NCP) . They foZhu et al. put forward a color attenuation prior (CAP)  to recovHowever, it is difficult to realize parallel acceleration due to the need to calculate various complex statistics from the image by manually selecting prior information, which leads to time-consuming dehazing of a single image. In addition, because the manually selected prior information does not fully conform to the mode of haze image generation, the restoration effect of this kind of method has certain limitations in both objective indicators and subjective evaluation. Due to the different choices of the prior information, incomplete dehazing or color distortion often occur.Although the haze removal methods based on prior information have been successful to varying degrees, their performance is essentially limited by the assumptions adopted or the accuracy of the prior to the target scene , and theCai et al. proposed a trainable end-to-end network DehazeNet  in 2016,In the same year, Ren et al. proposed an image dehazing method using a multi-scale convolutional neural network . The algWith the success of the algorithm proposed by Cai, Ren and others, researchers began to shift their attention from the previous artificial selection to research on an image dehazing algorithm based on deep learning.Li et al. proposed the integrated dehazing network AOD-Net . AOD NetHe et al. proposed the densely connected pyramid dehazing network (DCPDN) , which cThe above research is based on the atmospheric scattering model and supervised learning to achieve image dehazing. Obviously, it is a natural idea to transform a foggy image into a fogless one based on the physical model, but the introduction of the physical model into image dehazing may also have some drawbacks. Therefore, some researches focus on image dehazing independent of the atmospheric scattering model.Ren et al. proposed a gated fusion network GFN  to restoLiu et al. proposed a grid dehazing network, GridDehazeNet . GridDehHong et al. proposed a knowledge distillation and demisting network KDDN  based onWith the development of unsupervised learning, some researchers also combine it with image dehazing. Engine et al. proposed cycle-dehaze , which dSince 2021, the field of image dehazing has developed rapidly, and more and more algorithms have emerged that can achieve impressive results on public datasets. In 2021, Wu et al. proposed AECR Net , which iWith the rapid development of deep learning in recent years, the effect of single image dehazing algorithm is getting better and better. The results obtained by many algorithms on public datasets tend to be saturated with the increase of the size of convolutional neural networks.The appearance of Transformer not only makes a breakthrough in advanced computer vision tasks, but also accelerates the performance improvement of image dehazing methods. As mentioned earlier, the DehazeFormer  scheme pIn view of the superior performance of Transformer in dehazing tasks and its rapid development trend, using Transformer as a part of the network structure can improve the network feature extraction and recovery capabilities. However, due to the use of long-distance attention mechanism, Transformer has certain limitations in its ability to model local details. Although the Swin-Transformer reduces this limitation, it still obtains the global representation of some large areas in the image when the network is shallow. The convolutional neural network (CNN), which has the characteristic of local connection, can be used for local modeling better than Transformer.For images, adjacent areas are highly correlated in terms of color and material at the low level and semantics at the high level. For the task of image dehazing, adjacent pixels tend to be approximately equal in terms of medium transmittance and haze concentration. Therefore, this paper proposes a new dehazing network based on the fusion of Transformer and convolution, which uses the local characteristics of CNN and Transformer’s powerful representation ability and global modeling ability to improve the performance of single image dehazing.This section first introduces the overall network structure of our Transformer–Convolution fusion dehazing network (TCFDN) and then further introduces the Transformer–Convolution hybrid layer used in the network.The network proposed in this paper adopts the self-encoder structure, one of the classic generation models in the field of image restoration. The network structure is shown in B represents the batch size of the image, three represents the number of channels of the input image, H represents the height of the image, W represents the width of the image), and then the size of the 32 convolution cores is The self-encoder consists of an encoder and a decoder. First, the fogged image with input size ology as  to fuse In this paper, a novel Transformer–Convolution hybrid layer is proposed, which aims to improve the dehazing ability of the network by utilizing the global modeling characteristics of Transformer and the local modeling characteristics of convolution. The structure of the Transformer–Convolution hybrid layer proposed in this paper is shown in In the whole network structure, the input of the Transformer–Convolution hybrid layer is a tensor with the shape of The authors in  proposedAlthough the model proposed in this paper has some similarities with the model proposed in , there amodel in  is the sThe Swin-Conv Block proposed by  simply sIn this paper, the adaptive fusion mechanism proposed in  is used First, we add the output of the Swin-Transformer and the output of the optional convolution block to gather the information of the two outputs. We use global pooling, two connected full connection layers and a sigmoid activation function to obtain the corresponding weight of each channel and adaptively fuse the output of the Swin-Transformer and the output of the optional convolution block. The adaptive fusion calculation formula is shown below.Through this adaptive fusion mechanism, the network can simultaneously use the information learned by Transformer and convolution. Moreover, the learnability of channel weights also enables the network to automatically select the information that is more conducive to the final haze-free image reconstruction learned by the Transformer and the convolution during the training process.Compared with the simple residual block used in , this paIn this paper, FA Block and deformable convolution proposed in FFA-Net  are usedAfter downsampling the image, six trans-attention-convolution-blending-layers and two Transformer-deformable-convolution-blending-layers were used. The Transformer-attention-convolution-blend-layer uses FA Block in the optional convolution block, while the Transformer-deformable-convolution-blend-layer uses deformable convolution in the optional convolution block. This asymmetric network structure also makes the network feature processing methods for different stages more diversified than using only a single convolutional block.After the Transformer–Convolution fusion dehazing network was proposed, detailed experiments were carried out to verify its effectiveness. This section compares the proposed demisting network with other algorithms and evaluates the performance of the proposed demisting network from different perspectives, such as the objective test results and subjective evaluation on the synthetic dataset and the subjective evaluation on the demisting effect of real haze images. In addition, a series of ablation experiments were conducted to prove the effectiveness of each module in the proposed dehazing network.This section first introduces some settings of the experiment. Secondly, the synthetic dataset used is introduced. Then, the objective test results of the proposed dehazing network on the synthetic dataset, the subjective evaluation on the synthetic dataset, and the subjective evaluation on the dehazing effect of the real haze images are introduced in turn. Finally, this section introduces a series of ablation experiments.This paper used Python to implement the proposed Transformer–Convolution fusion dehazing network. The Adam optimizer was used to train the model, and the exponential decay rate posed by  were adoposed by . During This paper mainly used synthetic datasets to evaluate the performance of the proposed Transformer–Convolution fusion dehazing network. In image dehazing tasks, the most widely used dataset is RESIDE . RESIDE In this paper, a traditional dehazing algorithm DCP  and eighIt can be seen from In this paper, two representative dehazing results in the indoor part of SOTS were selected to compare the subjective dehazing performance of different algorithms. The classical traditional dehazing method DCP and two more prominent algorithms in recent years, MSBDN and FFA Net, were selected for comparison.The dehazing results of various algorithms are shown in By subjectively evaluating the dehazing results of different algorithms, it can be found that the overall dehazing results of the traditional method DCP are darker due to the use of dark channel prior, and the dehazing results still contain haze residues b. For thIn order to further evaluate the ability of the algorithm proposed in this paper to remove haze from real haze images, a real haze image was selected for testing. DCP, MSBDN and FFA-Net were also used for comparison.It can be seen from Although the above subsections have made a horizontal comparison between algorithms from an objective and subjective perspective and verified the feasibility of the proposed Transformer–Convolution hybrid network, we still carried out a series of ablation experiments to prove that the proposed Transformer–Convolution hybrid layer is more capable of feature extraction and recovery than the Swin-Transformer and the convolutional neural network.The following network configurations were used for ablation experiments:Configuration 1: Replaced the Transformer–Convolution hybrid layer with the Swin-Transformer. That is, after four times of downsampling of the input image, eight Swin-Transformer blocks were used for image feature extraction and restoration.Configuration 2: Replaced the Transformer–Convolution hybrid layer with its corresponding optional convolution block. That is, after four times downsampling of the input image, six FA Blocks and two deformable convolutions were used to extract and restore the image features.Configuration 3: Transformer–Convolution fusion dehazing network proposed in this paper.The experimental settings and the selection of training and test sets were the same as those in It can be seen from The ablation experiments carried out in this chapter provide powerful data support for the Transformer–Convolution fusion dehazing network proposed in this paper and further verify the effectiveness of the network.This paper first introduces the research background and significance of image dehazing on the basis of a large number of research studies on image dehazing. After that, this paper proposes a dehazing network that combines the popular Transformer and a convolutional neural network (CNN) to make up for the shortcomings of the Transformer and the convolutional neural network individually. In order to verify the effectiveness of the Transformer–Convolution fusion dehazing network, we carried out a series of comparative experiments, using objective evaluation and subjective analysis to verify the feasibility of the algorithm from different perspectives, such as synthetic image dehazing and real image dehazing. The results show that the new dehazing network surpasses many existing dehazing algorithms in terms of both objective evaluation indicators and subjective visual perception. Our scheme is better than the state-of-the-art AECR-Net by 0.5dB on average in terms of PSNR, and 0.001 in terms of SSIM, which can also be proved by subjective evaluation. Finally, ablation experiments were carried out to further verify the theoretical basis of the proposed dehazing network.


Postpartum depression (PPD) is a complex combination of physiological, emotional, and behavioral alterations associated with postpartum chemical, social, and psychological variations. It does harm to the relationship between family members that could potentially last for years. However, standard depression treatments are not ideal for PPD, and the outcomes of these treatments are debatable. Transcranial direct current stimulation (tDCS) is an emerging technology that could provide patients with PPD with a safe and non-pharmacological treatment. tDCS can relieve depression by directly stimulating the prefrontal cortex through the excitatory effect of the anode. It may also ease depression indirectly by promoting the production and release of the neurotransmitter GABA. The mechanism of tDCS makes it an ideal therapeutic approach to treat PPD, although it has not been widely used, and its effect has not been evaluated systematically and effectively. A double-blind, randomized controlled trial will be conducted involving 240 tDCS-naive patients with PPD, who will be randomly divided into two groups. One group will receive routine clinical treatment and care with active tDCS, and the other group will receive routine clinical treatment and care with sham tDCS. Each group of patients will receive a 3-week intervention during which they will receive 20 min of active or sham tDCS 6 days per week. The Montgomery–Åsberg Depression Rating Scale will be administered before the intervention as a baseline and on each weekend throughout the intervention phase. Before and after the intervention, the Perceived Stress Scale and the Positive and Negative Affect Schedule will be evaluated. Side effects and abnormal reactions will be recorded during each treatment. As antidepressants are banned in the study, the results will not be affected by drugs and will therefore be more accurate. Nonetheless, this experiment will be conducted in a single center as a small sample experiment. Therefore, future studies are required to confirm the effectiveness of tDCS in treating PPD. Postpartum depression (PPD) is a complex combination of physiological, emotional, and behavioral alterations associated with postpartum chemical, social, and psychological variations , interpersonal psychotherapy (IPT), and social psychotherapy, which can be combined with antidepressants, such as tricyclic antidepressants or selective 5-hydroxytryptamine reuptake inhibitors. Nevertheless, it remains controversial whether the conventional treatment approaches for PPD are effective based on the effects of the treatment approaches mentioned above  is a non-traumatic, convenient, safe, and effective brain function therapy technique widely used in clinics. As a typical NIBS approach, transcranial direct current stimulation (tDCS) may be an effective brain stimulation medical technique with the potential to be an “optimal” treatment method for PPD. Additionally, tDCS, a local brain stimulation-based treatment approach, is dependent on the presence of abnormalities in the activity of the frontal lobe region of the brain, particularly the left and right dorsolateral prefrontal cortex (PFC)  protocol toP. This may be a guide to a larger multi-centered RCT that explicitly values the therapeutic effects of tDCS on the treatment of PPD. This study protocol may also be used to derive the initial impact dimensions for the sample size required to complete the most complete and reliable RCT.The RCT will involve recruiting patients with PPD for up to 1–2 years from professional postpartum psychological health projects in the Departments of Psychosomatic Medicine, Rehabilitation Medicine, Obstetrics, and Gynecology at the First Affiliated Hospital of Nanchang University. To recruit enough participants, leaflets and posters will be posted at the place of recruitment, and physicians will be informed about this study to assist in identifying qualified participants. The research coordinator conducted a baseline visit before the start of the active study to collect information on baseline demographics, to gain access to health services, and to gather baseline Montgomery-Asberg Depression Rating Scale (MADRS) measures.In addition to the intervention, sham control will also be carried out within the Core Clinical Experiment at the first Affiliated Hospital of Nanchang University by well-trained researchers to guarantee proper supervision throughout the procedures. The active period of the experiment involving altogether 18 intervention or sham control sessions lasting for 20 min for approximately 3 weeks (6 days per week). The researchers who manage the session will record the date of every visit, the participant's blood pressure and heart rate, the starting and finishing times of sham tDCS, and interruptions, if any. All confounding factors  will be analyzed. Outcome questionnaires will be collected from patients with PPD at three time points: before the procedures after enrollment (T1), 1 week after completing the procedures (T2), and 3 weeks after completing the procedures (T3). Follow-up questionnaires will be completed in person or by phone 8 weeks after completing the procedures. Patients will receive email updates concerning enrollment goals and the integrity of follow-up to help them to perceive the contributions that they made while participating in the study. Participants are then contacted with outcome information gathered and organized by professionally trained and experienced researchers. Personal outcome information is blind to the researchers, participants, and physicians who provided clinical treatment and care in the study group assignment.The flow diagram of this study design is shown in Potentially eligible participants will be recruited through the Internet, leaflets, and posters, and preliminary screening will be conducted by trained psychologists, rehabilitation physicians, and obstetricians or gynecologists on visits to the First Affiliated Hospital of Nanchang University. The researchers will then conduct further screening based on eligibility and exclusion criteria to identify eligible participants. Finally, all the participants will provide written informed consent.To be included in the study, the participants must meet the following criteria:(1) Be postpartum and at least 18 years old;(2) Satisfy the current criteria for the diagnosis of severe depression or at least a severe depression paroxysm of moderate severity based on the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5);(3) Have been provided with and have refused to take antidepressants prescribed by their attending clinicians at the recruitment location;(4) Be evaluated to qualify for outpatient psychiatric treatment by a chief researcher; and(5) Have never received tDCS but agree to this treatment approach and comprehend the interpretations of the study and the associated questionnaires.Participants will be excluded from the study if they(1) Fail to meet the criteria for the diagnosis of severe depression or the severe depression paroxysm of less than moderate severity at the time of the study;(2) Have been diagnosed with alcohol or substance use disorder by the DSM-5 within the last 6 months;(3) Have severe and active medical or neurologic disorders or a history of epilepsy;(4) Are taking carbamazepine (because it might reduce the effectiveness of tDCS therapy), benzodiazepines, or other anticonvulsants daily at the time of the study;(5) Have metal objects into the skull, electrically transplanted into the body, or transplanted to the scalp to stimulate the skin at the skin defect; and(6) Have serious physical diseases or complications cause the patients can't endure the tDCS stimulation.The sample size involved in this study will be based on that of previous studies. The improvements will be evaluated using identical sample sizes based on the following estimated formula:Following the informed consent process and the assortment of baseline information, individuals suffering from PPD who meet the eligibility criteria pertinent to this study will randomly receive active or sham tDCS. A study aide outside the confines of this study will present an assignment sequence using a randomized table of arranged blocks, and group distributions will be put into air-tight envelopes. The randomization identification numbers (RIDs) in the table will be stratified by the age of the newborn baby at enrollment to balance the gestational age of each group. Therefore, the first layer of RIDs will be distributed to participants who are <3 weeks into the postpartum period at the time of registration. The second layer of RIDs will be distributed to participants who are 3 weeks or more into the postpartum period. The experiment coordinator, while remaining blind to the group assignments, will select an envelope to include in the participants' chart. The experimenter will then open the envelope to ascertain the packet assignment, and program the tDCS device accordingly. The researchers will document the outcome measures objectively. The participants and researchers collecting maternal and infant clinical outcome data will also remain blind to the group distributions.As this will be a double-blind study, a third party not involved in the experiment will administer and supervise the blind strategies as follows:(1) Participants will not be permitted to open the envelopes in the order in which they will be involved in the study. Assuming a tDCS model of modes A and B, the study implementer will not have any knowledge of what the stimuli represented.(2) The A model represents an active stimulus, and the B model represents a sham stimulus. A third-party evaluator will evaluate the treatment results without information regarding the subgroup.(3) The first non-blind method will be conducted until the applied mathematical analysis is completed to overcome subjective tendencies among the analysts during the data analysis process. After statistical analysis, a second non-blinded test will be conducted to determine the intervention group.(4) Participants will be randomly asked whether they received an active or sham stimulus to ensure that they do not recognize the stimulation pattern.This study has been approved by the Ethics Committee of the First Affiliated Hospital of Nanchang University: Clinical Medicine Ethics Review [2015]043.This study aims to investigate the possibility of conducting a multi-centered RCT to assess the effectiveness of tDCS in the treatment of PPD. Therefore, the objectives of the dissemination plan associated with this study are as follows: (1) offering insight for future studies to provide evidence for a multi-centered study examining the efficacy of tDCS in the treatment of PPD and (2) raising awareness and interest among the community and public regarding the potential possibility of this treatment approach in preventing unfavorable maternal and infant outcomes. This approach can facilitate the overcoming of hindrances to treatment satisfaction by ensuring that a clear and impartial message is delivered to potential treatment users, thereby encouraging effective and timely decisions regarding treatment. The group involved in this study is linked to clinical brain stimulation programs, and retraining on the use of tDCS procedures can be offered. Study findings will be presented in peer-reviewed publications to facilitate the rationality of our outcomes. Additionally, individuals suffering from PPD, as well as their families, will be informed of the outcomes in an encouraging and non-stigmatizing manner, ensuring that we facilitate the mass interest in participating in larger treatment trials and the subsequent adoption of this treatment approach.Participants will be provided with a clear explanation of the purpose, process, risks, and benefits of this study, and all questions asked by participants with the intention of confirming their understanding of the study, the risks and latent benefits of being involved in the study, and their privileges as study subjects will be answered before they sign the consent papers. Patients are required to sign an informed consent document before participating in the study. Informed consent should be obtained prior to any research evaluation or procedures, and before any private information is recorded. During the study period, participants will have an opportunity to agree to continue using the study protocol. We will also request that subjects invite their family and friends to participate in an initial discussion about the study so that all individuals involved in deciding whether to enroll in the study have adequate information. We will guarantee privacy protection of personal information.The intervention group will receive active tDCS, as well as clinical treatment and nursing care. The control group will receive sham tDCS as well as clinical treatment and nursing care. The treatment will be administered six times per week for 3 weeks. Regarding quality management, all the processes involving associated protocols, treatment approaches, and assessments will be standardized and conducted by the therapists participating in this study.Patients with PPD will continue to receive clinical treatment and nursing care from their individual clinical programs throughout the trial. Their clinical treatment and nursing suppliers are will be blind to their group assignment. Clinical treatment and nursing care will not include the offer of antidepressants. If participants start taking antidepressants during the study, it will be recorded, and they will not be able to continue participating in the study. The record of antidepressants is shown in 2 (5 × 7 cm). The duration of the treatment will be set at 20 min per session, once a day for 6 days each week , and the cathode on the upper edge of the right track. Based on a previous professional study, the current strength will be set at 2.0 mA  If a severe adverse reaction occurs during the intervention process, it will be terminated promptly to protect the participant.(2) The intervention will be terminated if a serious complication or worsening situation occurs during the intervention.(3) The intervention will be terminated if the participant requests to withdraw, does not accept the treatment, or does not cooperate.(4) If the therapist repeatedly explains that the treatment approach is not working, the study will be suspended.(5) The intervention will be terminated if the subjects have suicidal intentions, mental disorders, treatment for sudden mania, or acute maternity complications throughout and following treatment (as determined by the study team).Participants will have autonomy over their involvement in the study and can discontinue at any stage. The researchers will record in detail the reasons why and when participants drop out of the study. Participants who discontinue the treatment early will be included in an intention-to-treat analysis, which can be used to obtain follow-up information if the participants are willing.The main outcome measures for the study are feasibility, accessibility, and compliance with the trial protocol. Feasibility describes how well the trial protocol can be implemented. We record data on practicability related to eligibility , recruitment , and timing (including the time participants started treatment). We also ask patients with PPD whether they can distinguish which treatment (active tDCS or sham tDCS) they have received at the end of the procedure during the study period to assess the feasibility of our blinding methods. Accessibility refers to patients' satisfaction with and opinions on the intervention, focusing on maternal, neonatal, and infant outcomes, and on whether they experience any effects or adverse outcomes. Acceptability measures include participants' vital signs monitored during each session, the effects or adverse outcomes monitored at the end of each week of the study period, and questionnaires to assess maternal outcomes. Aiming to improve the precision of self-reported assessments of these health indices, we provide patients with PPD with a duplicate of the relevant questionnaire. Finally, we will take some measures to assess compliance, including the number of sessions attended during the overall and expected active study period, the number of patients who completed the 15 active study periods, the reasons for dropping out, and the proportion of follow-up data collection.The primary outcome will be the severity of depression symptoms evaluated by the MADRS  , which provides an assessment of these affects, will be used in this study , the participants can be referred for a clinical evaluation to evaluate their prognosis and their status of disability.t-test groups will also be performed. Ordinary-level variables with non-normal distributions will be compared statistically using the Mann–Whitney U test. Metrics with discrete distributions will be expressed as percentages and analyzed using χ2 or Fisher's exact test, as applicable. The general linear or logistic models will be used if needed to adjust the obfuscation effect.The results of the test will be analyzed using the Statistical Package for the Social Sciences, version 21.0. In the descriptive analysis of the samples, continuous variables with normally distributed data will be expressed as means and standard deviations whereas continuous variables with non-normally distributed data will be expressed as medians and interquartile ranges. Statistical comparisons of normally distributed data packages between t-test or Mann–Whitney U-test will be used. If statistically significant, the inequalities will be considered for confounding factors in the final efficacy analysis. To compare one or two outcomes between the two groups, continuous data will be analyzed using the t-test or the non-parametric test, and the data will be parsed using the Pearson χ2 test or Fisher's precision test. To control for possible confounding variables, linear models or linear regression models will be used for dependent continuous and dependent categorical variables. Repeating measure data will be used in the analysis of variance. The primary and secondary outcomes analyses will depend on intention-to-treat (ITT) and per-protocol (PP) bases. The results from ITT analyses will be compared with those from PP analyses to determine whether they are consistent. Missing data will be used as the final bearer for observation. The side effects will be displayed and parsed using a χ2 test or Fisher's precision test.To compare the baseline characteristics between the intervention group and the control group, the Safety and side effects will be evaluated daily throughout the active period of the study and at each follow-up and will be conventionally censored by the chief researchers. The study investigator team will provide the researchers with collective expertise in brain stimulation. Researchers will evaluate and audit safety during this pilot study. Mental health problems that require urgent medical attention will be conveyed to the researchers. Such mental health problems include self-destructive intention, homicidal intent, concern about child harm, evidence of psychotic symptoms, or any other related mental health issues based on the researchers' judgment. Urgent medical requests from participants will be treated appropriately to ensure their wellbeing. In such cases, the researchers will terminate the session (if this occurs during treatment), keep the participant in the office, and contact the psychiatrist for further directions. The psychosomatic medicine specialist will immediately evaluate the patient as required, with input from a specialist in maternal medicine. If no imperative medical or significant mental health conditions are found to be supported by this clinical evaluation, the participant will be directed to their psychosomatic care supplier, and, if necessary, the participant will be instructed to receive emergency services. When a participant's adverse event is recorded over the phone, emergency services will be contacted. Adverse events will be recorded and immediately reported (by telephone or fax within twenty-four hours) to the research ethics committees of both institutions to consider serious action, for example, the suspension of the intervention, the withdrawal of the participant, or the termination of the study.tDCS is a novel, noninvasive therapeutic approach for treating PPD and has the potential to introduce a safe, effective, low-cost, and accessible method of treatment. The study protocol presented in this paper is a pilot RCT that aims to guide the development of a larger multi-center study on determining the efficacy and safety of tDCS as a treatment option for PPD. The main site of tDCS is located at the left dlPFC, as the prefrontal cortex (PFC) has extensive and close relationships with the center and the remaining regions of the brain. Additionally, the PFC plays a key role in organizing, guiding, regulating, and processing information received within the brain, thereby making the overall function of the central nervous system harmonious  techniques, such as functional magnetic resonance imaging, electroencephalography, and magnetoencephalography, are powerful tools for studying the human brain and laying methodological foundations for cognitive neuroscience (Li et al., High-resolution modeling can be used to calculate the directional development of the spatial distribution of electric fields in the brain to understand how various stimulation parameters affect the current in neural tissues (Boayue et al., Furthermore, because the experiments associated with this study will involve a small sample, in our future studies on tDCS, we shall strive to provide a novel medical foundation for treating patients with PPD using tDCS. As a result of the high prevalence and impact on patients' lives, tDCS plays a significant role in seeking additional effective treatment approaches for PPD. Additional tDCS trials or the treatment of PPD will provide unique insights into this subject. This trial is a meaningful exploration of enhancing the treatment for PPD. The number of PPD patients continues to increase, highlighting the importance of establishing effective and time-saving treatment techniques for this population. In the future, RCTs should be conducted on the premise of medical ethics and safety. Additionally, it is important that the screening of the target population follow clear and appropriate guidelines to avoid deviation of the experimental results. Increasing sample sizes along with the provision of exact experimental data can improve the likelihood of providing individuals with the best treatment methods available.This trial was registered by the Chinese Clinical Trial Registry, ChiCTR2000029031. This study was registered on January 11, 2020.The research study has been approved by the Ethics Committee of the First Affiliated Hospital of Nanchang University: Clinical Medicine Ethics Review [2015]043.WS, GY, and QZ designed the study. GL, XK, and MS wrote the manuscript. XD and ZZ collected the clinical data. KZ performed statistical analyses. All authors contributed to the editorial changes in the manuscript, read, and approved the final manuscript.