Fire detectors arrangement presents a very important task in fire protection. This task was defined by valid standards. Although the standards should be equal or at least similar, there are situations where different standards demand different rules about detectors arrangement. One of those specific situations is the corridor case. Corridor definition is different from standard to standard, so as smoke detectors arrangement in corridors. This is especially interesting with the presence of some disturbing factors, such as airflow. This paper has been written to show smoke detectors arrangement in corridors according to the five leading standards in the field of fire protection, potential airflow influence on smoke detectors reaction in dependence of different detectors arrangement and different fire location, such as advantages of simulation software usage.
{"title":"Airflow influence on smoke detectors arrangement in corridors","authors":"R. Jevtić","doi":"10.5937/str1903030j","DOIUrl":"https://doi.org/10.5937/str1903030j","url":null,"abstract":"Fire detectors arrangement presents a very important task in fire protection. This task was defined by valid standards. Although the standards should be equal or at least similar, there are situations where different standards demand different rules about detectors arrangement. One of those specific situations is the corridor case. Corridor definition is different from standard to standard, so as smoke detectors arrangement in corridors. This is especially interesting with the presence of some disturbing factors, such as airflow. This paper has been written to show smoke detectors arrangement in corridors according to the five leading standards in the field of fire protection, potential airflow influence on smoke detectors reaction in dependence of different detectors arrangement and different fire location, such as advantages of simulation software usage.","PeriodicalId":33842,"journal":{"name":"Scientific Technical Review","volume":"80 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71085024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Gligorijević, V. Rodić, Bojan Pavkovic, J. Bogdanov, S. Živković, Z. Bajić
Rocket motor propellant grain, cast or bonded into the motor chamber or solid coating, is exposed to various loads during its service life. Rocket propellant is a viscoelastic material, whose mechanical properties strongly depend on temperature and strain rate. Application of cyclic loads, primarily thermal, onto a rocket motor on the field stock, may cause an undesirable mechanical damage of the grain. Over time, after long storage, it may grow up and lead to the grain failure. One of the ways for evaluation of this phenomenon is to determine a cumulative damage law. In this example, this law has been evaluated for hydroxy terminated polybutadiene (HTPB) composite rocket propellant by exposing a number of specimens to different long term stress levels. Using this law, it is possible to calculate a probability of failure and time distribution of the structural reliability of the grain in order to determine the useful life. Besides, the analysis has shown that there is a possible correlation between tensile strength of the propellant and the cumulative damage law. This fact can be used instead of carrying a longterm experiment for the exact determination of the law
{"title":"Effect of cyclic loads on structural damage of rocket propellant grain","authors":"N. Gligorijević, V. Rodić, Bojan Pavkovic, J. Bogdanov, S. Živković, Z. Bajić","doi":"10.5937/str1902008g","DOIUrl":"https://doi.org/10.5937/str1902008g","url":null,"abstract":"Rocket motor propellant grain, cast or bonded into the motor chamber or solid coating, is exposed to various loads during its service life. Rocket propellant is a viscoelastic material, whose mechanical properties strongly depend on temperature and strain rate. Application of cyclic loads, primarily thermal, onto a rocket motor on the field stock, may cause an undesirable mechanical damage of the grain. Over time, after long storage, it may grow up and lead to the grain failure. One of the ways for evaluation of this phenomenon is to determine a cumulative damage law. In this example, this law has been evaluated for hydroxy terminated polybutadiene (HTPB) composite rocket propellant by exposing a number of specimens to different long term stress levels. Using this law, it is possible to calculate a probability of failure and time distribution of the structural reliability of the grain in order to determine the useful life. Besides, the analysis has shown that there is a possible correlation between tensile strength of the propellant and the cumulative damage law. This fact can be used instead of carrying a longterm experiment for the exact determination of the law","PeriodicalId":33842,"journal":{"name":"Scientific Technical Review","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71084711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Radivojević, B. Pavić, A. Lebl, Milena Petrović
Malicious drones jamming is a subject of numerous researches in the world. The implemented jamming strategy is different in various cases and each improvement in the analysis, modeling and realization contributes to the jamming procedures originality. In this paper, we have analyzed implementation performances of sweep jamming with discrete subbands. This advanced method allows decreasing the problems caused by drone communication and/or telemetry signals jamming on the undesired disruption of navigation signals (GPS and GLONASS) used for the localization of friendly devices in the drone vicinity. The problem is analyzed on the example of one signal frequency intended for drone communication with its operator. Drones with this specific signal frequency are used relatively rarely, but the obtained results are the most illustrative for practical consideration of the problem. The specificity of this frequency is that it is nearest to the navigation signal frequencies which means that important conclusions made for this frequency are satisfied significantly easier for other frequencies intended for drone communication, video and telemetry signals transmission.
{"title":"Sweep jamming with discrete subbands: An advanced strategy for malicious drones missions prevention","authors":"J. Radivojević, B. Pavić, A. Lebl, Milena Petrović","doi":"10.5937/str2102046r","DOIUrl":"https://doi.org/10.5937/str2102046r","url":null,"abstract":"Malicious drones jamming is a subject of numerous researches in the world. The implemented jamming strategy is different in various cases and each improvement in the analysis, modeling and realization contributes to the jamming procedures originality. In this paper, we have analyzed implementation performances of sweep jamming with discrete subbands. This advanced method allows decreasing the problems caused by drone communication and/or telemetry signals jamming on the undesired disruption of navigation signals (GPS and GLONASS) used for the localization of friendly devices in the drone vicinity. The problem is analyzed on the example of one signal frequency intended for drone communication with its operator. Drones with this specific signal frequency are used relatively rarely, but the obtained results are the most illustrative for practical consideration of the problem. The specificity of this frequency is that it is nearest to the navigation signal frequencies which means that important conclusions made for this frequency are satisfied significantly easier for other frequencies intended for drone communication, video and telemetry signals transmission.","PeriodicalId":33842,"journal":{"name":"Scientific Technical Review","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71086028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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