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Issue Info: 
  • Year: 

    2013
  • Volume: 

    5
  • Issue: 

    4 (13)
  • Pages: 

    1-8
Measures: 
  • Citations: 

    0
  • Views: 

    908
  • Downloads: 

    0
Abstract: 

Star tracker is an attitude determination device which determines the satellite or spacecraft’s attitude using the Star position information in inertial and body references.Star information is collected and stored onboard as a “Star or mission Catalog”. There are several Star Catalogs that contain different kinds of information with different accuracy. In this paper the most used Star Catalogs are introduced and a few Star Catalog selection features are recommended. These features are weighted according to the Star tracker mission type. For the selected Star tracker mission, results demonstrate that Hipparcos Star Catalog is the best choice. Eventually using Hipparcos Star Catalog, a mission Catalog is developed to be used onboard a typical Star tracker.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    2018
  • Volume: 

    18
  • Issue: 

    6
  • Pages: 

    202-211
Measures: 
  • Citations: 

    0
  • Views: 

    635
  • Downloads: 

    0
Abstract: 

The size of database and minimum number of visible Stars in the field of view of Star sensor are two important, influential and contradictory parameters that should be considered in design of Star sensor. In this regard, the purpose of this paper is to unify the database using the uniform distribution of points on the celestial sphere with the triangulation method. For this purpose, the choice of the suitable Star Catalog, minimum suitable magnitude and elimination of double Stars are the other steps of the uniformity process that is carried out in this study. Thus, the results of the investigations showed that Delaunay's triangulation method is faster and more accurate than the geodesic grid. Also, by simulating and performing Monte Carlo tests to count the number of Stars observed in the different FOVs of a typical sensor, it was found that Delaunay's triangulation leads to a significant reduction of the probability of viewing the high density of the Catalog Stars in the field of view, so that the probability of observation more than 25 Stars in all possible FOVs has reached to zero. On the other hand, for observing 4 or more than 4 Stars at a confidence level more than 95% in non-uniform Catalog, the field of view needs to be at least 12. 5 degrees, while in uniform database; this field is slightly increased to more than 13 degrees. In other words, uniformity has increased the minimum field of view needed to see the minimum number of required Stars.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    2021
  • Volume: 

    14
  • Issue: 

    2 (پیاپی 47)
  • Pages: 

    103-110
Measures: 
  • Citations: 

    0
  • Views: 

    54
  • Downloads: 

    4
Abstract: 

In this paper, a new algorithm for determining the density of scattered data at the surface of the sphere is presented and then the proposed algorithm along with Geodesic Weighted K-Means clustering and Deluany triangulation are used to make uniform Star Catalogs. Comparison of the results with the results of other related articles shows that the proposed algorithm resulted in a significant decrease in the probability of observing a large number of Stars in all simulated Star sensor fields of view. This improvement is due to the uniformity of the Star Catalog, especially in the celestial sphere poles due to the proposed density determination algorithm. On the other hand, the use of a proper data density algorithm has increased the likelihood of observing a few Stars (such as 3 or 5) in all fields of view used in the Monte Carlo simulation.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    2016
  • Volume: 

    9
  • Issue: 

    2
  • Pages: 

    85-90
Measures: 
  • Citations: 

    0
  • Views: 

    1042
  • Downloads: 

    0
Abstract: 

Attitude Determining is one of the major and critical satellites space missions. In this study, a new method to Attitude determination of satellites is presented. Such that, based on the proposed method search space will be more limited then accuracy and speed of attitude determination in the proposed method has risen. At first in this method, implementation and the test algorithms will be discussed, after these some algorithms, such as navigation, pattern recognition and ultimately attitude determination will be reviewed. In order to implement these algorithm. High quality images of Stars which must provided by the Star tracker camera requires to implement. Really these images to perform the necessary processing sent to the processor so the processor based on designed algorithms, determines the attitude of camera and satellite in all three axes. This means that some features considered for Star tracker and based on them begins the designing process. The range of accurately determination for Star tracker is one of these features. In this article, the ranges of two axes of Yao and Pitch less than 20 seconds on the scale of degree are considered and in the roll axis less than 100 seconds is intended. Can show in the results, much better accuracy and less than initial assumptions have been achieved. It also carried out by an adaptive identified algorithm so that the brighter Stars are identified and based on their attitude determination, the sensor accuracy have increased. Because of according research, the clearer Stars, have more accurate in calculation. The other important feature is the speed of attitude detection which performed by 1 GHz processor, and correct identification of pyramidal algorithm where have reached less than 15 milliseconds. Due to the duration, the desire update rate gained. Other important parameters which influence the accuracy of the attitude determination is knowing the exact coordinates of the intersection point vector of focal length lens with image sensors. By Land calibration for camera with a good accuracy, these parameters were estimated.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Author(s): 

POO D.C.C. | KHOO CH.S.G.

Issue Info: 
  • Year: 

    2006
  • Volume: 

    8
  • Issue: 

    4 (32)
  • Pages: 

    133-162
Measures: 
  • Citations: 

    0
  • Views: 

    926
  • Downloads: 

    0
Abstract: 

The Online Public Catalog (OPAC) is an information retrieval system characterized by short bibliographic records, mainly of books, journals, and audiovisual materials available in a particular library. This is coupled with Boolean search interface and heterogeneous user problems for subject searching by end users. To perform effective subject searching in the OPAC system requires a wide range of knowledge and skills. Various approaches to improving the OPAC design for subject searching have been proposed and are reviewed in this article. The trend toward Web-based OPAC interfaces and the developments in internet and digital library technologies present fresh opportunities for enhancing the effectiveness of the OPAC system for the subject searching.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    0
  • Volume: 

    1
  • Issue: 

    1
  • Pages: 

    0-0
Measures: 
  • Citations: 

    1
  • Views: 

    348
  • Downloads: 

    0
Keywords: 
Abstract: 

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    2023
  • Volume: 

    30
  • Issue: 

    5
  • Pages: 

    85-94
Measures: 
  • Citations: 

    0
  • Views: 

    136
  • Downloads: 

    23
Abstract: 

Background & Aims: Schizophrenia is a mental disorder with frequent psychosis, whose symptoms include delusions, hallucinations, disordered speech or behavior, and impaired cognitive ability. The cause of this disease becoming a debilitating disorder for patients and their families is its early onset and chronic course, which affects one percent of the population. Antipsychotic drugs are only effective in treating half of the patients, and the pathological mechanism of schizophrenia is not fully understood. In addition, these drugs improve generally positive symptoms (such as hallucinations and thought disorders that are at the core of the disease), but negative (such as social isolation) and cognitive symptoms (such as learning and attention disorders) remain untreated. On the other hand, these drugs have severe neurological and metabolic side effects and may lead to sexual dysfunction. Schizophrenia is a multifactorial disorder that involves the interaction of several genes, environmental factors, and epigenetic processes. Over the past ten years, genetic research has yielded new findings that have given rise to hope for the biological origins of schizophrenia. The genetic role is caused by a large number of alleles, including alleles with small effects that can be identified by GWAS studies. The drug treatments that are available for schizophrenia have poor efficacy for many patients in which the mentioned genetic factors are very effective.  Identifying the causes of this disease is an important step in the field of improving the treatment for this disorder, which is estimated to be half to one third of the genetic factors influencing the development of schizophrenia by common alleles reported in GWAS studies. Thus, GWAS studies are potentially an important tool for understanding the biological process of schizophrenia. GWAS Catalog is a complete collection of all published studies at the genome level, which makes it possible to investigate and identify the cause, understand the mechanism of the disease, and identify new treatment methods in this disease. In recent years, many efforts have been made to identify biomarkers in the diagnosis, prevention and treatment of schizophrenia, each of which introduces specific genes and pathways that overlap with other mental disorders. In this study, in order to investigate important genes and biological pathways in the development of schizophrenia, the genes reported in the GWAS Catalog bioinformatics database were examined so that in the future, with more studies, it can help to treat and diagnose these patients more accurately. Methods: In the present study, using the GWAS Catalog database and searching for the word Schizophrenia, a list of 3344 SNPs was extracted from 80 research articles. In the next step, the SNPs that cause schizophrenia and other related diseases were extracted (1165 SNPs that were the result of 19 studies). Then, among the SNPs obtained in the previous steps, those with lower and equal p-values were 5*10^-8, isolated and checked using ensemble.org in the BioMart section, in order to find the closest genes. Then, the results of BioMart were sorted and collected based on the obtained genes, and the duplicates were removed (removal of duplicate genes) and finally 336 genes were obtained. (In general, for 554 SNPs, the gene was identified, and for the other 574 SNPs, the gene name was not found, which are extragenic.) In the next step, the above list was entered in BioMart and the names of the desired genes were obtained. (Part of Ensemble genes 107; NCBI gene (formerly Entrezgene) accession) which resulted in a total of 339 genes. In the last step, the genes obtained from the previous step were checked using the Enrich R site, and through this site, the pathways that were related to the studied genes were extracted and compared with the results of different articles. Results: In this study, after entering the results in Biomart, 339 genes were obtained. Also, after entering the above list in the Enrich R site, the important pathways in which these genes are active were obtained. Pathways which Adjusted-P value was below 0.05 were considered as reliable results. Conclusion: This study was conducted on schizophrenia by analyzing the data of GWAS Catalog database to identify the mechanism of the disease and the pathways involved as well as the main and important genes of drug candidates. One of the important pathways in this study was Glucuronidation, which was one of the first pathways obtained from Wiki Pathway studies, which is often involved in the metabolism of substances such as drugs, pollutants, bilirubin, androgens, estrogens, mineralocorticoids, glucocorticoids, fatty acid derivatives, retinoids. and bile acids play a role. This pathway is mainly carried out in the liver, although the enzyme responsible for its catalysis. UGTs are widely expressed in the brain, but at lower levels than in the liver. Brain UGTs are inducible or inhibitable that affect drug release in the central nervous system. UGTs, cytochrome P450s, and transporters act together to influence the pharmacokinetics of drugs in the brain. After glucuronidation, many drugs have the ability to cross the blood-brain barrier. Another pathway is ascorbate metabolism. Ascorbate (vitamin C) is a vital antioxidant molecule in the brain. However, it has several other important functions, participating as a cofactor in several enzymatic reactions, including catecholamine synthesis, collagen production, and HIF-1α regulation. Ascorbate is transported to the brain and neurons through the sodium-dependent vitamin C transporter (SVCT2), which causes the accumulation of ascorbate in cells against a concentration gradient. The highest concentrations of ascorbate in the body are found in the brain and neuroendocrine tissues such as the adrenals, although the brain is the hardest organ to deplete ascorbate. Together with the regional asymmetry in the distribution of ascorbate in different regions of the brain, this shows the important role of ascorbate in the brain. The next pathway was the porphyrin metabolism pathway, which disruption in this pathway can cause neurological symptoms, neuropathy and a wide range of psychiatric symptoms in addition to specific diseases, until in 1939, Waldenstrn reported that schizophrenia in families with Acute intermittent porphyria (AIP) is very common, but no statistics were provided. Another study found that 5 of 40 AIP probands had hallucinations, suggesting a possible link between psychosis and AIP. A study in Sweden found that people with AIP were four times more likely to develop schizophrenia or bipolar disorder. In addition, first-degree relatives of these people are twice as likely to be diagnosed with schizophrenia and bipolar disorder. The other pathway was the pathway of retinoid metabolism, the first evidence linking this pathway to schizophrenia is that retinoid toxicity or deficiency frequently leads to the manifestation of symptoms that, although more severe in scope, are similar to those of schizophrenia. For example, mental disorder, mental defect, large ventricles, microcephaly and various major and minor congenital anomalies, among which cranial anomalies are prominent. Such deficits have been reported frequently among schizophrenic samples. With the increasing documentation of the prominent role of retinoids in the development of the central nervous system, the possibility of retinoid involvement in schizophrenia is strengthened. Another important pathway was drug metabolism, which drugs that are widely used today in the treatment of mental disorders, including depression, psychosis, and mood stabilizers, in many cases are associated with many side effects, and only a small number of patients respond appropriately to These drugs show Many factors, including genetic factors, are effective in the effectiveness of drugs, which are of interest today. According to the present study, it can be concluded that genetics and especially polymorphisms play a very important role in the development of schizophrenia and that these genes can be used in the diagnosis and treatment of this disease. In the future, the genes of these pathways can be studied more reliably in schizophrenia for diagnostic and therapeutic purposes. The genes obtained in this research can be suitable and new options for future studies on schizophrenia and optimization of treatment methods.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    2006
  • Volume: 

    7
  • Issue: 

    5
  • Pages: 

    551-561
Measures: 
  • Citations: 

    0
  • Views: 

    308
  • Downloads: 

    161
Keywords: 
Abstract: 

Iran Strong Motion Network (ISMN) Started its activities in 1973 and running by Building and Housing Research Center (BHRC) since 1981. At the date of this study ISMN consist of more than 1103 digital (SSA-2) and 52 analog (SMA-1) accelerographs. The accelerograms of different earthquake, are downloaded, controlled, processed, and then added to the comprehensive data bank, which is very useful for scientists and engineers. In this Catalog the most important earthquakes are briefly described. More information is presented in Table 1 and also available on the web page of BHRC (http://www.bhrc.ac.ir).

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    2006
  • Volume: 

    7
  • Issue: 

    6
  • Pages: 

    695-709
Measures: 
  • Citations: 

    0
  • Views: 

    582
  • Downloads: 

    265
Keywords: 
Abstract: 

In the first half of the year 2006, 327 accelerograms (with PGA greater than the trigger level of 0.01g) were recorded by 108 accelerographs, which were triggered by 200 earthquakes with different magnitude. The Silakhor earthquake of 3/31/2006 in Lorestan province was the strongest earthquake in the studied period that triggered 29 accelerographs and the maximum PGA of about 0.524g was occurred in ChalanChoolan station. In this article the most important earthquakes and those with more than three or more accelerograms in the studied time period are discussed in brief and the detailed information is presented in the finale table.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    2010
  • Volume: 

    11
  • Issue: 

    5
  • Pages: 

    663-674
Measures: 
  • Citations: 

    0
  • Views: 

    592
  • Downloads: 

    153
Abstract: 

Iran Strong Motion Network (ISMN) Started its activities in 1973. Iran Strong Motion Network had 1087 digital (1082 SSA-2 and 5CMG-5TD) and 13 analog (SMA-1) accelerographs in operation in 2007. The accelerograms of different earthquake, are downloaded, controlled, processed, and then added to the comprehensive data bank, which is very useful for scientists and engineers in the field of engineering seismology and earthquake engineering. In the second half of the year 2007, 124 accelerograms (with PGA greater than the trigger level of 0.01g) were recorded by 91 accelerographs, which were triggered by 69 different earthquakes. The maximum PGA of about 0.148g was occurred in Tabriz station (Eastern Azerbaijan Province).

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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