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Blind Channel Estimation and Equalization
Said Elkassimi,Said Safi,B. Manaut 보안공학연구지원센터 2016 International Journal of Multimedia and Ubiquitous Vol.11 No.12
This paper presents the problem of blind channel estimation of a non-minimum phase system using three algorithms. These algorithms play an important role for blindly estimate the parameters of radio mobile channel. Thus studying the problem of blind channel equalization based on, the proposed algorithm, CMA and SKMAA algorithms. The simulation results in noisy environment and for different SNR values demonstrate that the proposed algorithm is more performing than other algorithms. In addition the Sign Kurtosis Maximization Adaptive Algorithm (SKMAA) is more powerful in comparison to constant modulus algorithm (CMA) at the blind channel equalization, that is to say gives the right equalization.
Safi, Yaser,Amid, Reza,Zadbin, Fariba,Ahsaie, Mitra Ghazizadeh,Mortazavi, Hamed Korean Academy of Oral and Maxillofacial Radiology 2021 Imaging Science in Dentistry Vol.51 No.-
Purpose: Dental implants are widely used for the rehabilitation of edentulous sites. This study investigated the occurrence of dental implant malpositioning as shown on post-implantation cone-beam computed tomography (CBCT) and to identify related factors. Materials and Methods: Samples with at least 1 malpositioned dental implant were collected from a central radiology clinic in Tehran, Iran from January 2017 to January 2019. Variables such as demographic characteristics, length and diameter of implants, type of implant, sites of implant insertion, different types of implant malpositioning problems (cortical plate perforation, interference with anatomical structures), angulation of the implant, and the severity of malpositioning were assessed. In addition, the incidence of implant fracture and over-drilling was evaluated. Data were statistically analyzed using the chi-square test, 1-sample t-test, and Spearman correlation coefficients. Results: In total, 252 patients referred for implant postoperative CBCT evaluations were assessed. The cases of implant malpositioning included perforation of the buccal cortical plate (19.4%), perforation of the lingual cortical plate (14.3%), implant proximity to an adjacent implant (19.0%), implant proximity to an adjacent tooth (3.2%), interference with anatomical structures(maxillary sinus: 18.3%, mandibular canal: 11.1%, nasal cavity: 6.3%, mental foramen: 5.6%, and incisive canal: 0.4%). Implant fracture and over-drilling were found in 1.6% and 0.8% of cases, respectively. Severity was categorized as mild (9.5%), moderate (35.7%), severe (37.7%), and extreme (17.1%), and 52.4% of implants had inappropriate angulation. Conclusion: CBCT imaging is recommended for detecting dental implant malpositioning. The most common and severe type of malpositioning was buccal cortex perforation.
Safi, Yaser,Kadkhodazadeh, Mahdi,Safai, Pooria,Esmaeelinejad, Mohammad,Shamloo, Nafiseh Korean Academy of Periodontology 2014 Journal of Periodontal & Implant Science Vol.44 No.5
Purpose: This study aimed to assess the interdental bone level in premolar bitewing radiographs while retracting the cheeks. Methods: Seventy-two horizontal bone defects were created on dried mandibles and maxillae. The distance from the bone level to the cement-enamel junction of premolars was detected by a modified digital caliper (considered the gold standard). The reliability of all radiographs was assessed by intraclass correlation coefficient (ICC), and the validity was compared to the gold standard using the analysis of variance test. P-values less than 0.05 were considered statistically significant. Results: This study showed that the reliability of radiographs without a cheek simulator and with 0.16 second exposure time was significantly higher than that of the two other groups (ICC=0.96 compared to 0.93 and 0.88, respectively). The results from the radiographs without a cheek simulator and with 0.16 second exposure time were more similar to the gold standard measures than those of the two other groups, although the difference was not statistically significant. Conclusions: Retracting the buccal soft tissue plays an important role in increasing the accuracy of radiographs in detecting the interdental alveolar bone level and produces more accurate results than increasing the exposure time, although it does not have a significant role in reliability of results.
Safi Yaser,Amid Reza,Zadbin Fariba,Ghazizadeh Ahsaie Mitra,Mortazavi Hamed 대한영상치의학회 2021 Imaging Science in Dentistry Vol.51 No.3
Purpose: Dental implants are widely used for the rehabilitation of edentulous sites. This study investigated the occurrence of dental implant malpositioning as shown on post-implantation cone-beam computed tomography (CBCT) and to identify related factors. Materials and Methods: Samples with at least 1 malpositioned dental implant were collected from a central radiology clinic in Tehran, Iran from January 2017 to January 2019. Variables such as demographic characteristics, length and diameter of implants, type of implant, sites of implant insertion, different types of implant malpositioning problems (cortical plate perforation, interference with anatomical structures), angulation of the implant, and the severity of malpositioning were assessed. In addition, the incidence of implant fracture and over-drilling was evaluated. Data were statistically analyzed using the chi-square test, 1-sample t-test, and Spearman correlation coefficients. Results: In total, 252 patients referred for implant postoperative CBCT evaluations were assessed. The cases of implant malpositioning included perforation of the buccal cortical plate (19.4%), perforation of the lingual cortical plate (14.3%), implant proximity to an adjacent implant (19.0%), implant proximity to an adjacent tooth (3.2%), interference with anatomical structures (maxillary sinus: 18.3%, mandibular canal: 11.1%, nasal cavity: 6.3%, mental foramen: 5.6%, and incisive canal: 0.4%). Implant fracture and over-drilling were found in 1.6% and 0.8% of cases, respectively. Severity was categorized as mild (9.5%), moderate (35.7%), severe (37.7%), and extreme (17.1%), and 52.4% of implants had inappropriate angulation. Conclusion: CBCT imaging is recommended for detecting dental implant malpositioning. The most common and severe type of malpositioning was buccal cortex perforation.
Safi Ullah Khan,Naimat Ullah Khan,Asad Ullah 한국증권학회 2021 Asia-Pacific Journal of Financial Studies Vol.50 No.2
We investigate whether cross-country differences in the legal system influence demand-side credit constraints. We explore the notion of discouraged borrowers — firms that choose not to apply for bank credit because they anticipate rejection. Employing survey data from 46 economies, we find that rapid and less costly court proceedings, lower procedural complexity in court processes, and higher recovery rates under bankruptcy lead to the lower likelihood of borrower discouragement. These results are more pronounced in countries with strong creditor protections in relation to company reorganization and liquidation. The results corroborate the supply-side view that strong creditor rights and their efficient enforceability alleviate banks’ participation constraints in the loan market, thereby encouraging small and medium-sized enterprises to apply for credit in the first place. We also find that differences in institutional settings, such as higher regulatory quality, better control of corruption, and the rule of law, lead to lower rates of credit self-rationing in the loan market.