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In this research 52 species of bees (Hymenoptera: Apoidea) have been reported from the northeastern Fars province, of which the species of Hylaeus punctus Förster and Hoplitis leucomelana Kirby were new records for Iran fauna. Among the material examined, there were 11 species of Apidae, 19 species of Halictidae, 1 species of Andrenidae, 4 species of Colletidae and 17 species of Megachilidae. Phoretic mites belonging to four genera Parapygmephorus, Vidia, Imparipes and Anoetus were associated with halictid and meghachilid bees. Among associated mites with collected bees Imparipes burgeri Ebermann & Jagersbacher-Baumann belonging to the family Scutacaridae was new for Iran fauna and Asia. We also collected five new mite species for science. These species were belong to the genera Parapygmephorus (1 species), Vidia (1 species), and Anoetus (3 species) of the families Neopygmephoridae, Winterschmidtiidae and Anoetidae respectively that will be described elsewhere. All specimens are deposited in the “Collection of Iranian Pollinator Insects” of Yasouj University.

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The males of the three species of bumblebees, Bombus (Thoracobombus) ruderarius (Müller), B. (T.) persicus Radoszkowskiand B. (T.) mesomelas Gerstaecker collected from Vikan village, Qazvin province and their male labial gland secretions were analyzed by gas chromatography/ mass spectrometry (GC/MS) and components of their extracts were identified. The major compounds were a complex mixture of alkenols, alkenals, fatty acids, hydrocarbons, wax type esters and steroids. The main component of male labial gland secretions of B. ruderarius, B. persicus and B. mesomelas were determined to be 9-hexadecenol (42.1%), Z-13-octadecen-1-yl acetate (81.8%) andZ-12-pentacosene (34.4%), respectively. Results showed that if detection of species in male bumblebees would be difficult by using morphologic characters, then identification could be confirmed by detecting main component of male labial gland of these bees.

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In this study 46 species of bees (Hymenoptera: Apoidea) and their 17 associated mite species from Chaharmahal and Bakhtiari province reigns with some specimens collected from Yasouj and Dezful have been examined. Four species of mites were new for Iran: Sennertia zhelochovtsevi Zachvatkin, Vidia lineata Oudemans, Sennertionyx manicati (Giard) and Crabrovidia oudemansi Fain. These mites were found on bees’ families of Halictidae, Megachilidae, Apidae and Andrenidae. The identified mites were belonging to families of Neopygmephoridae, Scutacaridae, Chaetodactylidae, Anoetidae, Acaridae, Saproglyphidae and Winterschmidtiidae. Among bees’ families, the most association was observed on Halictidae and the lowest was on Andrenidae. Bee species of Halictus (Halictus) resurgens Nurse, 1903 had the highest percentage of association. All specimens are deposited in the Iranian Pollinator Insects Museum of Yasouj University. Herein a list of mite species associated with bees and bees’ species list are provided. Some specimens belong to genera of Imparipes Berlese, 1903 (n=12 specimens) and Chaetodactylus Rondani, 1866 (n=11 specimens) were new for science which would be described in a subsequent paper.

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In this survey, 154 bee species of Apoidea superfamily, from the western part of the Isfahan province, Iran were recorded, of which 29 species are new for the fauna of Iran. Among the identified specimens, there were 35 species of Andrenidae, 11 of Apidae, 20 of Colletidae, 50 of Halictidae, 36 of Megachilidae and 2 of Melittidae. All specimens are deposited in the Museum of Iranian Pollinating Insects of Yasouj University, Yasouj, Iran.

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There is not a comprehensive cheklist on Halictidae family in Iran yet. In this survey, 1179 specimens of the Halictid bees collected from various area of Iran were examined. Among them, we found 78 species of Halictid bees as a major component of the Apoidea fauna in Iran. Herein, a list of the halictid bees, with localities name, geographical coordinations of localities, and number of male and female specimens is provided. Also, distribution of species in Iran, based on the material collected in this study and the worldwide distribution (where applicable) are presented. Five species are recorded for the first time from following provinces, respectively: Lasioglossum (Ctenonomia) vagans (Smith, 1857), from Sistan-o Baluchestan, Halictus (Vestitohalictus) nasica Morawitz, 1876, from Isfahan and Sistan-o Baluchestan, Halictus tetrazoinus (Klug, 1817) from Charmahal-o Bakhtiari, Halictus fatsensis Blüthgen, 1936, from Charmahal-o Bakhtiari, Halictus (Seladonia) fuscicollis Morawitz, 1876, from Sistan-o Baluchestan.

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This study examines the impact of organizational communication on human resource management architecture which is conducted in one of the governmental agencies. This research is an applied research and is a descriptive survey. Data collected using questionnaire consisted of three parts, first, demographic information. Second, effective organizational communication assessment which is based on six components of Robbins model and consists of 37 questions. Third, measurement of human resource management architecture which consists of 19 questions from (readers et. al 2012). as reliability and validity of measuring instruments confirmed, population of this study is managers and employees of Khorasan-e-Razavi, which 280 of them randomly selected as the study sample. Data Analyzed using SPSS and LPS software. results show that effective organizational communication has a significant positive relationship with human resource management architecture and contribute to its implementation.

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Background: Prediction of future climate change is based on output of global climate models (GCMs). However, because of coarse spatial resolution of GCMs (tens to hundreds of kilometers), there is a need to convert GCM outputs into local meteorological and hydrological variables using a downscaling approach. Downscaling technique is a method of converting the coarse spatial resolution of GCM outputs at the regional or local scale. This study proposed a novel hybrid downscaling method based on artificial neural network (ANN) and particle swarm optimization (PSO) algorithm. Materials and Methods: Downscaling technique is implemented to assess the effect of climate change on a basin. The current study aims to explore a hybrid model to downscale monthly precipitation in the Minab basin, Iran. The model was proposed to downscale large scale climatic variables, based on a feed-forward ANN optimized by PSO. This optimization algorithm was employed to decide the initial weights of the neural network. The National Center for Environmental Prediction and National Centre for Atmospheric Research reanalysis datasets were utilized to select the potential predictors. The performance of the artificial neural network-particle swarm optimization model was compared with artificial neural network model which is trained by Levenberg–Marquardt (LM) algorithm. The reliability of the models were evaluated by using root mean square error and coefficient of determination (R²). Results: The results showed the robustness and reliability of the ANN-PSO model for predicting the precipitation which it performed better than the ANN-LM. It was concluded that ANN-PSO is a better technique for statistically downscaling GCM outputs to monthly precipitation than ANN-LM. Discussion and Conclusions: This method can be employed effectively to downscale large-scale climatic variables to monthly precipitation at station scale.

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Aims: Water is a basic demand of sustainable development in every region of the world. Hirmand catchment is one of the most important cross-border of Iran basins affected by the recent drought periods from water scarcity and caused severe crisis in the Sistan region. Fuzzy theory is able to convert most incorrect and enigmatic concepts, variables and systems into a mathematical form and set the context for reasoning, deduction and decision making at uncertainty conditions. The aim of this study was to simulate the Hirmand catchment by Water Evaluation and Planning System (WEAP) model and prioritization of the implementation of agriculture development projects in Hirmand catchment.
Materials & Methods: In this analytical-computational study, water development projects in the study area were predicted. The effects of the water development projects predicted using WEAP model and the projects according to the economic criteria was evaluated and prioritized with Fuzzy Technique for Order Preference by Similarity to Ideal Situation (TOPSIS). Ten water development projects and criteria including 5 economic indexes were considered.
Findings: Water transfer project to agricultural field called Zehak and Sistan were the first priorities which is needed for noticing target population to these projects. Irrigation efficiency (70%) was in the third rank among the options.
Conclusion: The remarkable thing in the ranking of scenarios is that the current account scenario (SC₁) is lasted ranking that shows Sistan region's water status, according to the study criteria is not good. 

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In this study, the distribution of 88 species of the family Megachilidae, out of 3678 specimens in the Iranian Pollinator Insects Museum of Yasouj University (IPIM), which were collected in spring and summer 2009–2017 from different regions of Iran including Ardabil, Chaharmahal-o Bakhtiari, Fars, Golestan, Isfahan, Kerman, Khuzestan, Kohgiluyeh-va Boyer-Ahmad, Sistan-o Baluchestan, Alborz, are presented. Data on the number of specimens, locations, coordinates and distribution maps for Iran and global distribution of all species (where available) are also provided. Megachile (Megachile) octosignata Nylander 1852 is first recorded from Iran. Ninetheen species are reported for the first time from Chaharmahal-o Bakhtiari and Kohgiluyeh-va Boyer-Ahmad Provinces.

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 So far, various translations of Nahj al-Balaghah into Persian have been made, but in general, due to the shortcomings in the translation of Arabic into Persian, these translations have been criticized by some litterateurs. The present study critiques the lexical aspect of the translation of "Derivatives of Estef’al" in the sermon of Nahj al-Balagheh. Since one of the most important tools to eliminate translation deficiencies is scientific critique and evaluation using literary science e.g. vocabulary, grammar, syntax and rhetoric, and an important prerequisite in this category is familiarity with vocabulary. Ignoring of vocabulary causes serious harms to translation. This research addresses the harms related to issues in understanding the semantic meaning of terms, including (disregard of the root-meaning of the word, disregard for the meanings of the subject, omission, and so on) and in this case, 5 Persian translations of the sermon of Nahj al-Balaghah (Faiz al-Islam, Dashti, Shahidi, Ansari and Zamani), by referring to the main literature of this aspect, and discovering the exact meaning of the word were reviewed. It should be noted that in the sermons of Nahj al-Balaghah, the derivatives of the "Estef’al" have been used 293 times, and 35 lexical mistakes have been found.
 

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Efficiency and productivity are conception that input and output proportions one economic system determine. Data envelopment analysis (DEA) is suitable instrument for calculation efficiency one establishment, but one of the difficulties this model is decision maker can not interment terms of risk and uncertainty in result, in one hand in searches in agricultural sector decision maker hardly with terms of risk and uncertainty confront. Interval data envelopment analysis method (IDEA) a useful instrument in efficiency of evaluation so much establishment take into terms of risk, uncertainty and inexact data. In this search with use of IDEA model provinces of country efficiency in basis animal husbandry in country with consider key input and output in this industry studied. Conclusion say Ardebil province most efficiency and Booshehr province lower most efficiency in basis milky cow-keepers and also Khozestan province most efficiency and Chahar Mahal Bakhtiyari province lower most efficiency in basis fattened cow-keepers in country. Statistics that used in this search it concern five years.

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Aim: The present study aimed to investigate the relationship between the Nurse Competency Predicting Scale (NCPS) scores and those of the Principles and the course of Techniques of Nursing Procedures (PTNPs), particularly its theoretical and practical units, among nursing students.
Instrument & Methods: This cross-sectional study was conducted on the new entrance nursing students at the Guilan University of Medical Sciences. In total, 175 nursing students were recruited by the census method. Then, the NCPS was completed online, and the data analysis was performed using the Pearson correlation coefficient, ANOVA, and t-test by SPSS 21.  
Findings: The mean NCPS score of the students was 73.14±10.23. A statistically significant relationship was observed between the nursing students’ paramedic clinical experience, reason for choosing nursing as their field of study, interest in studying nursing, desire to work in the nursing profession, and intention of doing a PhD degree and their NCPS scores (p<0.05). However, there was no statistically significant relationship between the NCPS scores and scores of the course of PTNPs, and the first internship scores (p>0.05).
Conclusion: The capacity to acquire NC among the new entrance nursing students is at a high level. Here, the students with the intention of doing a PhD, and a history of paramedic clinical experience, interested in studying nursing and working in the nursing profession reported a higher NC. Considering these key factors during university admissions can be suggested to strengthen NC in the nursing profession.

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Aims: In the past years, the increase in economic pressures and the shrinking of families and the motivation to live a simple life have caused an increase in the demand for small-scale houses. The purpose of this research is to identify the framework and ranking of flexibility components that can be effective in small-scale housing.

Methods: In this research, using the descriptive-analytical method, the effective components in the design of flexible small-scale houses were identified and the conceptual framework of the research was confirmed using the Delphi method. Then, using the survey method, these components were ranked in the 10th district of Isfahan through Shannon's entropy test. The statistical population includes three groups of experts, architectural experts and the public, whose opinions have been compared and analyzed using comparative analogy.

Findings: The research findings show that the components that are important from the point of view of all three groups include: multi-functional spaces, mezzanine spaces, adaptable facade with variable uses, use of shallow plans with rectangular geometry, movable furniture according to ergonomics and movable partitions according to It is ergonomic.

Conclusion: In the end, it can be concluded that among the identified components, several components such as partitions and movable furniture are compatible with human ergonomics and adaptable view, and modern technology is an important tool to achieve them.
 

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Comparative assessment of genetic diversity of 122 durum wheat genotypes (Triticum turgidum L. var. durum) was performed using 73 SSAP polymorphic fragments, 123 AFLP polymorphic loci and 104 SSR alleles. SSAP and AFLP data showed a clear demarcation between the cultivars and landraces and SSR data classified cultivars and landraces according to their origin. Furthermore, the estimated genetic diversity of Iranian landraces was higher compared to the foreign entries and a loss of genetic diversity was observed from landraces to cultivars. This study determined that differences in genetic relationships revealed by SSAP, AFLP and SSR distances could not be attributed solely to differences in the level of polymorphism detected by each marker system. The molecular evidence of genetic diversity decrease of the durum wheat gene pool further strengthens the strategic relevance of undertaking appropriate genetic conservation measures for food security.

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Doogh is a traditional Iranian fermented milk drink, which is produced by lactic fermentation of pasteurized milk. In order to isolate and identify the microorganisms present in Iran industrial Doogh samples, polymerase chain reaction (PCR) was applied. Doogh samples were 17 name brands. After conducting the preliminary identification by microscopic observations and biochemical tests, in order to verify the obtained results the samples were pure-cultured which was followed by PCR and sequencing. According to the results obtained through sequencing of 16S rRNA, the identified bacteria belonged to lactic acid bacteria (Lactobacillus brevis, L. fermentum, L. paracaseiand L. gallinarum); gram-posetive spore-forming bacteria (Bacilluslicheniformis, B. anthracis and B. subtilis) and acetic acid bacteria (Acetobacter tropicalis and A. indonesiensis). Moreover, based on the results obtained by sequencing of D1/D2 26S rDNA the identified yeasts were including Pichia fermentans, Saccaromyces unisporous and Cryptococcus magnus. The obtaining of present study illustrated that in addition to identified non-starter lactic acid bacteria, other types of bacteria and yeasts were found in Iran industrial Doogh samples.

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Aims: In contemporary residential architecture, semi-open spaces have lost their quality as one of the essential spaces of a home. Therefore, the aim of this research is identifing the components that increase the quality of semi-open residential spaces and assessing the level of intersections and differentiation of these components in literature review and contemporary residential architecture of the country.

Methods: The components of semi-open spaces were identified using a descriptive method, and then 30 case studies in IRAN were evaluated using a cese study method. The frequency and weight of the components were obtained based on Shannon's entropy in the literature and case studies. Subsequently, a comparative analysis was conducted between the prioritization of components between literature review and case studies.

Findings: the intersectional components of semi open space include diverse activities and spaces, desirable activities, view, interaction with environment, privacy and natural elements, adjacency to interior spaces, spatial dimensions - height, spatial proportions, openness, materials, and spatial construction elements. The semantic differentiations are as follow social interaction, safety, and comfort are protorized in the literature review, while aesthetic components such as restraint, visual continuity, and beauty are protorized in case studies. The physical differentiations are such that the literature emphasizes the physical structure, including surface areas, porosity, spaciousness, and depth of space, whereas the case studies illustrate a superiority of aesthetic considerations, involving color, volumetric balance, and form.

Conclusion: After considering the intersectional semantic and physical components as primary design imperatives, the differences indicate that what is crucial in enhancing the quality of semi-open spaces in contemporary residential works is desires, housing budgets, and socio-cultural requirements of diverse contexts.
 

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Comment marketing is a digital strategy that uses hashtags and mentions to attract users to websites or Instagram pages. This study sheds new light on the effects of topic drift in comment marketing on customers' shopping attitudes. Accordingly, a mixture of qualitative and quantitative methods was used. A sample of 5,000 views from the most popular posts by Digikala Holding Company in 2021-2022 was randomly selected for a qualitative investigation. Following that, 460 views were purposefully selected to be investigated using the integrated research method. Following a review of the most relevant research related to the research variables and based on the qualitative results, the conceptual model of the article was developed. Then, based on the conceptual model of the research, a questionnaire was conducted. After approving the content validity and reliability of the questionnaire, it was administered to 366 Instagram users. Based on research data obtained through a survey and questionnaire test, the analysis of the structural equation method was used to create a pattern based on the study's statistical population. The results showed that Instagram users use various break mechanisms - parasite, mutual referential, and republishing - to disrupt the speech chain to attract users to their Instagram page or website. Furthermore, the break mechanisms of topic drift in the marketing strategy have a linear, positive, and significant effect on social network users' shopping attitudes. Compared to the parasite and republish mechanisms of the break in comment marketing, the mutual reference mechanism positively impacts users' shopping attitudes.


1. Introduction
The digital revolution has placed a whole new set of capabilities in the hands of consumers and businesses. Following that, marketing has not only focused on satisfying consumer needs. Instead, it prefers to empower and enable users to construct the realities which they intend to experience through the construction of communities. Due to this, digital marketing through social networking enables companies to communicate with their customers at relatively low costs. Thus, commenting is one of the online marketing methods that allow users to introduce their content to their website through the sharing of an access link toward their Instagram page, website, or other websites. 
In comment marketing, companies often try to direct the customer to their page by changing the topic or breaking the chain of speech during the discussion of a brand post. In other words, by examining the conversation process - which can be short or long - one can see that the topic at the end of a conversation is very different from that of the beginning. This topic shift has occurred gradually and users are usually unaware of this event. In fact, the ideal conversation is not one in which the chain of turns revolves around a single topic. Instead, there should be a proper balance between the steps that are related to the topic and the steps that take the conversation in a new direction. 
From the viewpoint of discourse as a process, communication and coherence are the consequences of the interaction between users that can be achieved by mutual efforts of both the communicator and the audience. Accordingly, this research is aimed at answering the question that "in the online written conversation, what mechanisms of topic drift are used in the comment marketing to affect the users' shopping attitudes?" Therefore, the first hypothesis of the study is: "The use of topic drift mechanisms of break in comment marketing can affect social network users' shopping attitudes" (The main hypothesis). According to this hypothesis, there are three sub-hypotheses: first, the use of parasitic mechanisms in the comment marketing strategy negatively affects the shopping attitude of users (sub-hypothesis one)." Secondly, the use of mutual reference mechanisms in comment marketing has a positive effect on the shopping attitude of users (sub-hypothesis two). Lastly, the use of republishing mechanisms in comment marketing has a negative impact on the shopping attitude of users (sub-hypothesis three).
In order to discover unknown layers of meaning in a systematic way, a mixed method consisting of qualitative and quantitative methods was applied. Following a review of the most relevant research related to the research variables and drawing upon the qualitative results, the conceptual model of the article was developed. Then, on the basis of a conceptual model of the research, a valid and reliable questionnaire was conducted. Based on research data obtained through a survey and questionnaire test, the analysis of the structural equation method was used. This analysis is used to create a pattern based on the statistical population of the study. 

2. Literature Review
Due to the fact that communication in cyberspace has led to the emergence of extensive communication platforms among the customer (Baker, 2003; Kotler & Keller, 2006; Fırat & Dholakia, 2006; Kotler et al., 2018; Ajina, 2019; Algharabat et al., 2018; Kapoor et al., 2018; Kaur et al., 2018; Lal et al., 2020; Lopes & Casais, 2022), commentary has become a central issue in digital marketing (Bahtar & Muda, 2016; Aibing, 2018). By developing the strategy of comment marketing (Lee et al., 2020; Aibing, 2018;), companies often try to direct the customer to their page by changing the topic or breaking the chain of speech during the discussion of a brand post (Eisend, 2016; Lee et al., 2020). 
However, by looking at the conversation process, one can see that the topic of the conversation ended up being very different from the topic at the beginning of the conversation (Razeghi et al., 2020a; Razeghi et al., 2020b; ). This topic shift, or according to Hobbs (1990, 1) topic drift in the written dialogue (Danesi, 2018; Nouruzi & Arjmandi, 2021; Yus, 2010) has occurred gradually and users are usually unaware of this event (Razeghi et al., 2020a; Tanskanen, 2006). In this regard, coherency (Halliday & Hasan, 1976; Mann & Thompson, 1987; van Dijk, 1977; Schank, 1977; Daneš, 1978; Goutsos, 1997; Halliday, 1985; Abbasi, 2001) and topic drift in discourse analysis (Sarnovsky & Kolarik, 2021; Button & Casey, 1984; Myers, 1998; Hobbs, 1990; Herring & Nix, 1997; Herring, 2003; Razeghi et al., 2020 b) which can inevitably be a controversial issue has not been considered. By considering the vital role of user shopping attitude in the field of marketing, various types of research from a psychological point of view (de Matos et al., 2007; Ajzen & Fishbein, 1980; Schiffman & Kanuk, 1997) in relation to marketing (Kotler et al, 2018; Setiyawati et al., 2017; Holt, 2002; Touzé, 2020; Eisend, 2016) have applied this concept. Meanwhile, the contribution of linguistic and discourse research in this field is very small and is limited to only a few studies (Phillips & Hardy, 1997; Park & Lee, 2019). Despite this interest, no one to the best of our knowledge has studied comment marketing from a discourse analysis point of view on shopping attitude.

3. Methodology
Digi-Kala Instagram's page as one of the most popular holding companies was analyzed during 2021-2022. Instagram had a lower filtering rate during this period when compared to other social networks in Iran, increasing its engagement rate. For this purpose, a mixture of qualitative and quantitative methods was used to reveal hidden layers of meaning in a systematic way. As part of a qualitative investigation, a sample of 5000 views published under the most viewed posts published by Digikala's Holding company in the period of 2021-2022 was randomly selected. Following that, 460 views were purposefully selected to be investigated using the integrated research method. Following a review of the most relevant research related to the research variables and based upon the qualitative results, the conceptual model of the article was developed. Then, based on the conceptual model of the research, a questionnaire was conducted. After approving the content validity and reliability of the questionnaire, it was administered to 366 Instagram users. Based on research data obtained through a survey and questionnaire test, the analysis of the structural equation method was used to create a pattern based on the statistical population of the study. After that, the software application used to analyze the data was Amous (0.89 version).

3. Theoretical basis
3. 1. Integrated model
Coherence and topic relevance is a macro-semantic structure, also called the subject of discourse (van Dijk, 1977). It is formed hierarchically by smaller structures (van Dijk, 1977). In conversations, there are general and specific topics that are either covered by the whole conversation or simply by one utterance. Moreover, topics are included in one another and organized in a kind of hierarchy of sub-topics inside topics. In stepwise movement, "any next utterance is built in such a way as to be on topic with a last" (Sacks, 1992b, 300). The stepwise movement involves the development of a topic, while the boundary movement concerns the boundary between topics. In the development of a topic, there is another type of movement which is less controlled and slower than stepwise movement which is "topic drift" (Hobbs, 1990).
In conversations, we find general and specific topics that cover the whole conversation or are contained within one utterance. Moreover, topics are included in one another and organized in a kind of hierarchy of sub-topics inside topics. In stepwise movement, "any next utterance is built in such a way as to be on topic with a last" (Sacks, 1992b, p. 300). In this sense, a stepwise movement concerns the development of a topic whereas a boundary movement concerns the limits between topics. 
In the development of a topic, there is another type of movement which is less controlled and slower than stepwise movement which is "topic drift" (Hobbs, 1990). Hobbs (1985) classified topic drift as 1) a kind of association based on sematic parallelism, 2) chained explanations, or explanations that become topics in their own right, and c) metatalk (evaluation) used as a way of introducing a novel topic (Hobbes, 1985, 3-9). Hobbs (1985) suggests that subsequent discourse segments shift the subject through parallelism, explanations, or metatalk. Herring and Nix (1997) added break to this division. Parallel moves include the introduction of different entities with the same properties as those already mentioned, or other properties of the same entities. Explanations expand on the topic at hand by explaining a previous proposition. Metatalk serves to structure the discourse. Break changes the topic. (Herring and Nix, 1997, 4). In addition to this break, Razeghi et al (2020) add three subclasses: A) Parasite: advertising text intended to be followed by users, B) mutual reference, mention to other matters outside or other sides of the Instagram page, C) republishing: tagging users or mentioning a subject by using # or @ (Razeghi et al., 2020). In general, the mechanism of topic drift and break is shown in the below figure.

Figure 1
 Coherence and Topic drift mechanisms




    



Similarly, the soft and flexible nature of the market in social networks constantly encounters consumers with novel products to influence their shopping attitude (De Matos et al., 2007). Attitude refers to how people view the world. Consumers’ attitude is guided by their beliefs which determines their behavior and purchase intentions. In general, intentions to perform a behavior will be influenced by individual and interpersonal characteristics (Kotler and Armstrong, 2018). 
A large and growing body of literature has investigated the coherence and the topic of discourse (Hobbs, 1990). In addition, more recent attention has focused on the effects of topic drift on conversation flow (Razeghi et al, 2020). Previous work has only focused on the strategy of comment marketing, but the mechanisms of topic drift in comment marketing have not been studied so far. 

3. 2. Conceptual model
The qualitative findings in this study revealed that some users, by publishing their comments, attempt to break the written discourse chain. In addition, they direct traffic by linking to their own website or Instagram page. Hence, it could conceivably be hypothesized that "the usage of topic drift mechanisms in comment marketing has an impact on the shopping attitude of social network users" (The main hypothesis)". This hypothesis itself consists of three sub-hypotheses as "by using Parasite, mutual reference and republishing mechanisms in the comment part of a post, we can have a negative effect on users' shopping attitudes (Hypothesis one)."
In general, on the base of previous studies and our research qualitative investigation, the following conceptual model was obtained, which was used to measure the users of the questionnaire as follows:


Figure 2
Conceptual model of research





4. Results
Research data will be analyzed using structural equation modeling in this section. The structural equation method can study the causal relationships between variables. In general, the hypothesis under consideration in a model of structural equations is a causal structure observed among a set of invisible structures. These structures are measured by a set of observer variables. In this research, Amous software has been used to analyze the structural equations of the proposed research model (Ebrahimi et al., 2022).
Structural equation analysis can be explained with two models of measurement and structural. In this regard, by confirming the data fitness, the investigation of each model will be complete. Fitness is a scale between 1 and -1. Accordingly, as long as a variable's fitness amount is close to one, its effect is higher. Therefore, if the number 1 is obtained, it is the exact variable. If this value is -1, it means that the variable in question has an effect but its effect is reversed.

4. 1. Measurement model
The fitness of our conceptual model is reported based on a set of fitness indicators in the table below. From all the mentioned indicators, it can be seen that the research model has a good fit with the studied data.

Table 1
 Model fit (linear regression)
                Estimate    S.E.    C.R.    P    Label
Shopping attitude    <---    Break        .446    .065    6.908    ***    
Q5    <---    Break        1.000                
Q6    <---    Break        .999    .049    20.588    ***    
Q7    <---    Break        .998    .047    21.291    ***    
Q8    <---    Break        1.015    .049    20.623    ***    
Q9    <---    Break        .965    .049    19.772    ***    
Q10    <---    Break        .829    .052    15.991    ***    
Q16    <---    Shopping attitude        1.000                
Q15    <---    Shopping attitude        .495    .162    3.061    .002    
Q14    <---    Shopping attitude        .328    .149    2.198    .028    
Q13    <---    Shopping attitude        .665    .169    3.929    ***    
Q12    <---    Shopping attitude        .952    .191    4.984    ***    
Q11    <---    Shopping attitude        1.825    .279    6.530    ***    

The table above shows that the relationship between the latent variables and the shopping attitude is significant.
Also, the table below shows the standardized regression coefficient of the relationships between the variables. In general, the standardized regression coefficient of the relationships between the variables, which is often 0.5, indicates the high intensity of this relationship. In general, based on the table below, it can be seen that the relationship between research variables is positive and direct.



Table 2
 Model fitness (standardized linear regression)
            Estimate
Shopping attitude    <---    Break    1.000
Q5    <---    Break    .835
Q6    <---    Break    .859
Q7    <---    Break    .877
Q8    <---    Break    .860
Q9    <---    Break    .838
Q10    <---    Break    .727
Q16    <---    Shopping attitude    .359
Q15    <---    Shopping attitude    .180
Q14    <---    Shopping attitude    .124
Q13    <---    Shopping attitude    .246
Q12    <---    Shopping attitude    .352
Q11    <---    Shopping attitude    .660

According to the fitness model, there is a very high and acceptable relationship between the variables. By studying the questionnaire's internal structure and discovering the independent and latent variables contained within each structure, it was determined that the structures used to measure the independent and present variables are quite appropriate and have the ability to measure these variables.

4. 2. Structural model
The tested conceptual model is presented in the figure below. The numbers written on the lines are actually beta coefficients from the regression equation between the variables, which is the path coefficient.




Figure 2
 Tested research model (path coefficients and operating loads)
 

The above structural model shows the internal relationship between research variables. Indices of the latent variable "topic drift" were evaluated with 12 independent variables. Among these indicators, break with 6 independent variables (parasite with 2 independent variables, mutual reference with 2 independent variables, and republishing rupture with 2 independent variables) were measured. Also, the indicators of shopping attitude as a latent variable were measured by 6 independent variables which were positive, linear, and meaningful.
In general, by analyzing the internal structure of the questionnaire and discovering the constituent factors of each construct or latent variable, and using confirmatory factor analysis tools, it was found that the structures used to measure latent variables are quite suitable for the ability to measure these variables. 
In sum, the aim of this study was to investigate the effect of break mechanisms of topic drift on the shopping attitude of social network users. In this regard, some users attempted to break the chain of written discourse by publishing their comments in order to introduce other brands' Instagrams/websites. Based upon quantitative investigation, it was founded that Instagram users benefit from various break mechanisms including parasite, mutual referential, and republishcation to disrupt the speech chain and then attract users to their Instagram page or website. Furthermore, the break mechanisms of topic drift in comment marketing have a linear, positive, and significant effect on social network users' shopping attitudes. Compared to the parasite and republish mechanisms of the break in comment marketing, the mutual reference mechanism has a positive impact on users' shopping attitudes. In this regard, the optimal agreement between the structured model and the experimental data was studied. Then, by applying the structural equations, an appropriate model was designed for the relationship between latent and explicit variables. Finally, the research findings showed that interactive discourse mechanisms can play an influential role in comment marketing due to their capabilities. It is undeniable that identifying and discovering elements of the marketing discourse perspective can contribute to changing users' attitudes as well as building a lasting connection with them.

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In this paper, a trajectory tracking control strategy for a quadrotor flying robot is developed. At first, dynamic model is obtained by lagrange-euler approach. Then, control structure, consisting of a model-based predictive controller, has been used based on state space error to track transitional movements for reference trajectory and also robust nonlinear H∞ control is applied for stabilizing the rotational movements and reject the external disturbance. In both controllers the integral of the position error is considered, allowing the achievement of a null steady-state error when sustained disturbances are acting on the system. The external disturbances is considered as aerodynamic torques. If uncertainties increase, the designed control system will be unable to track and stabilizing perform properly and completely. So finally, in order to eliminate the effects of parameter uncertainties the recursive least squares is used for estimating mass and moment inertia parameters which are linear and it is applied to the control system. Simulation results show that by using estimation of system parameters, the proposed control system has a promising performance in terms of stabilization and position tracking even in the presence of external disturbance and parametric uncertainties.