Considering snowmelt in mountainous areas as the important source of streamflow,the snow accumulation/melting processes are vital for accurate simulation of the hydrological regimes.The lack of snow-related data and i...Considering snowmelt in mountainous areas as the important source of streamflow,the snow accumulation/melting processes are vital for accurate simulation of the hydrological regimes.The lack of snow-related data and its uncertainties/conceptual ambiguity in snowpack modeling are the different challenges of developing hydroclimatological models.To tackle these challenges,Global Gridded Snow Products(GGSPs)are introduced,which effectively simplify the identification of the spatial characteristics of snow hydrological variables.This research aims to investigate the performance of multisource GGSPs using multi-stage calibration strategies in hydrological modeling.The used GGSPs were Snow-Covered Area(SCA)and Snow Water Equivalent(SWE),implemented individually or jointly to calibrate an appropriate water balance model.The study area was a mountainous watershed located in Western Iran with a considerable contribution of snowmelt to the generated streamflow.The results showed that using GGSPs as complementary information in the calibration process,besides streamflow time series,could improve the modeling accuracy compared to the conventional calibration,which is only based on streamflow data.The SCA with NSE,KGE,and RMSE values varying within the ranges of 0.47–0.57,0.54–0.65,and 4–6.88,respectively,outperformed the SWE with the corresponding metrics of 0.36–0.59,0.47–0.60,and 5.22–7.46,respectively,in simulating the total streamflow of the watershed.In addition to the superiority of the SCA over SWE,the twostage calibration strategy reduced the number of optimized parameters in each stage and the dependency of internal processes on the streamflow and improved the accuracy of the results compared with the conventional calibration strategy.On the other hand,the consistent contribution of snowmelt to the total generated streamflow(ranging from 0.9 to 1.47)and the ratio of snow melting to snowfall(ranging from 0.925 to 1.041)in different calibration strategies and models resulted in a reliable simulation of the展开更多
Fundamental characteristics of the plastic-scintillating fiber (PSF) for wide energy range of electromag- netic radiation (X & γ) have been studied to evaluate possibility of using the PSF as an imaging detector ...Fundamental characteristics of the plastic-scintillating fiber (PSF) for wide energy range of electromag- netic radiation (X & γ) have been studied to evaluate possibility of using the PSF as an imaging detector for industrial purposes. Monte-Carlo simulation program (GEANT4.5.1, 2003) was used to generate the data. In order to evaluate image quality of the detector, fiber array was irradiated under various energy and fluxes. Signal to noise ratio (SNR) as well as detector quantum efficiency (DQE) were obtained.展开更多
Fundamental characteristics of the plastic scintillating fiber (PSF) as a detector for electromagnetic radiation (X & γ) are obtained by GEANT4 detector simulation tool package. The detector response to radiation...Fundamental characteristics of the plastic scintillating fiber (PSF) as a detector for electromagnetic radiation (X & γ) are obtained by GEANT4 detector simulation tool package. The detector response to radiation with energy of 10~400 keV is found out. Energy deposition as well as detector efficiency (DE) of the PSF are studied. In order to make linear array of the PSF for imaging purpose, the optimum length of fiber is also estimated.展开更多
AIM To assess the association of inter-ethnic vs intra-ethnic marriage with severity of coronary artery disease(CAD) in men undergoing angiography.METHODS We conducted a prospective multicenter,multi-ethnic,cross sect...AIM To assess the association of inter-ethnic vs intra-ethnic marriage with severity of coronary artery disease(CAD) in men undergoing angiography.METHODS We conducted a prospective multicenter,multi-ethnic,cross sectional observational study at five hospitals in Saudi Arabia and the United Arab Emirates,in which we used logistic regression analysis with and without adjustment for baseline differences. RESULTS Data were collected for 1068 enrolled patients undergoing coronary angiography for clinical indications during the period of April 1^(st),2013 to March 30^(th),2014. Ethnicities of spouses were available only for male patients. Of those enrolled,687 were married men and constituted the cohort for the present analysis. Intra-ethnic marriages were reported in 70% and inter-ethnic marriages in 30%. After adjusting for baseline differences,interethnic marriage was associated with lower odds of having significant CAD [adjusted odds ratio 0.52(95%CI:0.33,0.81)] or multi-vessel disease(MVD) [adjusted odds ratio 0.57(95%CI:0.37,0.86)]. The adjusted association with left main disease showed a similar trend,but was not statistically significant [adjusted odds ratio 0.74(95%CI:0.41,1.32)]. The association between interethnic marriage and the presence of significant CAD and MVD was not modified by number of concurrent wives(P interaction > 0.05 for both).CONCLUSION Among married men undergoing coronary angiography,inter-ethnic,as compared to intra-ethnic,marriage is associated with lower odds of significant CAD and MVD.展开更多
AIM：To evaluate and compare structural optical coherence tomography（OCT）-based parameters,such as Bruch’s membrane opening-minimum rim width（BMO-MRW）,and retinal nerve fiber layer（RNFL）thickness in glaucoma pa...AIM：To evaluate and compare structural optical coherence tomography（OCT）-based parameters,such as Bruch’s membrane opening-minimum rim width（BMO-MRW）,and retinal nerve fiber layer（RNFL）thickness in glaucoma patients with visual field（VF）defects,and to correlate both to mean deviation（MD）values of obtained standard achromatic perimetry（SAP）examinations.METHODS：Patients with glaucoma and glaucomatous VF defects were enrolled in this prospective study and compared to age-matched healthy individuals.All study participants underwent a full ophthalmic examination and VF testing with SAP.Peripapillary RNFL thickness and BMO-MRW were acquired with SD-OCT.Correlation analyses between obtained global functional and global as well as sectorial structural parameters were calculated.RESULTS：A consecutive series of 30 glaucomatous right eyes of 30 patients were included and compared to 36healthy right eyes of 36 individuals in the control group.Global MD of values correlated significantly with global RNFL（Pearson corr.coeff：0.632,P=0.001）and global BMO-MRW（Pearson corr.coeff：0.746,P〈0.001）values in the glaucoma group.Global MD and sectorial RNFL or BMO-MRW values correlated less significantly.In the control group,MD values did not correlate with RNFL or BMO-MRW measurements.A subgroup analysis of myopic patients（〉4 diopters）within the glaucoma group（n=6）revealed a tendency for higher correlations between MD and BMO-MRW than MD and RNFL measurements.CONCLUSION：In a clinical setting,RNFL thickness and BMO-MRW correlate similarly with global VF sensitivity in glaucoma patients with BMO-MRW showing higher correlations in myopic glaucoma patients.展开更多
OBJECTIVE: To compare the efficacy of honey mouthwash 12.5% and chlorhexidine solution 0.2%to reduce the rate of oropharyngeal bacterial colonization in mechanically-ventilated patients.METHODS: This study was a rando...OBJECTIVE: To compare the efficacy of honey mouthwash 12.5% and chlorhexidine solution 0.2%to reduce the rate of oropharyngeal bacterial colonization in mechanically-ventilated patients.METHODS: This study was a randomized, single blind, phase Ⅲ controlled clinical trial. Sixty patients newly admitted to internal and trauma Intensive Care Units of the two educational hospitals of Sanandaj city affiliated with Kurdistan University of Medical Sciences were selected by convenience sampling and allocated to two groups of 30 patients using random blocks design. In each group,the mouthwash was applied twice a day for four consecutive days. Swab samples were taken from the mouth and throat of all patients three times a day(pre-intervention, two days, and four days after the intervention) and then the samples were transferred onto the blood agar and eosin methylene blue(EMB) culture plates and investigated for bacterial growth and colonization after 24-48 h.RESULTS: The findings showed that oropharyngeal colonization was not significantly different between the two groups, pre-intervention, two days,and four days after the intervention(P > 0.05). Rinsing with honey mouthwash 12.5% led to the inhibition of Staphylococcus aureus and Pseudomonas aeruginosa on the fourth day of the intervention in all samples.CONCLUSION: None of the studied solutions contributed to the reduction of oropharyngeal bacterial colonization. It seems that the growth inhibition of Staphylococcus aureus and Pseudomonas aeruginosa by the honey 12.5% mouthwash in mechanically-ventilated patients need further investigation.展开更多
It is important to assess image quality, in order to ensure that the imaging system is performing optimally and also identify the weak points in an imaging system. Three parameters mostly leading to image degradation ...It is important to assess image quality, in order to ensure that the imaging system is performing optimally and also identify the weak points in an imaging system. Three parameters mostly leading to image degradation are contrast, spatial resolution and noise. There is always a trade-off between spatial resolution and signal to noise ratio, but in scintillating fiber array detectors spatial resolution is not as important as signal to noise ratio, so we paid more attention to contrast and SNR of the system. By using GEANT4 Monte Carlo detector simulation toolkit, some effec- tive parameters of the linear plastic scintillating fiber (PSF) array as an imaging detector were investigated. Finally we show that it is possible to use this kind of detector to take CT and DR (Digital Radiography) image under certain conditions.展开更多
Water quality and occurrence of water-borne diseases in the Gaza strip are vivid examples for most developing societies. In recent years, the quality and quantity of groundwater, the only source of waters in the Gaza ...Water quality and occurrence of water-borne diseases in the Gaza strip are vivid examples for most developing societies. In recent years, the quality and quantity of groundwater, the only source of waters in the Gaza strip, have deteriorated markedly. A general rundown of the infrastructure and water distribution networks, in particular, the spread of cesspools, excessive use of pesticides and fertilizers, and improper treatment and disposal of wastewater remain major contributing factors to the continued deterioration in the water status in the Gaza strip. Without a doubt, the (Israeli)-Palestinian conflict had a clear negative impact on the water sector in the Gaza strip. Apparently, there is a dire need to adopt the WHO’s water safety plan in the management of Gaza’s water supply systems from catchment to consumer’s tap in order to maintain the sustainability and quality of water resources and prevent outbreaks of waterborne diseases. Therefore, this review has been prepared to highlight the overall picture of the water dilemma in the Gaza strip in the last years and in addition, to identify the sources, sorts, levels, and health risks of consequence to microbial contamination of water. The impact of political conflicts on the water sector in the Gaza strip also was reviewed. Furthermore, recommendations were formulated in order to assist and guide future researchers, stakeholders, and policymakers to avoid the more exacerbation of water contamination as well as to protect public health.展开更多
One-dimensional （1D） catalytic etching was investigated in few-layer hexagonal boron nitride （hBN） films. Etching of hBN was shown to share a number of similarities with that of graphitic films. As in graphitic fi...One-dimensional （1D） catalytic etching was investigated in few-layer hexagonal boron nitride （hBN） films. Etching of hBN was shown to share a number of similarities with that of graphitic films. As in graphitic films, etch tracks in hBN commenced at film edges and occurred predominantly along certain crystal directions of its lattice, though it was shown that the tracks were generally narrower than those of few-layer graphene under similar processing conditions. It was also shown that catalytic hydrogenation can occur completely through a few-layer hBN film, demonstrating that this process can be used in the formation of isolated low-dimensional nanoscale structures from other layered 2D materials beyond graphene. This ability for thin hBN films to be etched completely through allowed for a crystalline substrate to guide the etching process, which was demonstrated with the successful etch track formation of few-layer hBN on single-crystalline sapphire substrates. The substrate-guided etching resulted in parallel few-layer hBN nanoribbons having an average width of 32 nm and spacing of 13 nm.展开更多
This study involves the development of an analytical model for understanding the behavior of the extended, stiffened end-plate moment connections with eight high strength bolts. Modeling of the connection as an assemb...This study involves the development of an analytical model for understanding the behavior of the extended, stiffened end-plate moment connections with eight high strength bolts. Modeling of the connection as an assemblage of finite elements (FE) used for load deformation analysis, with material, and contact nonlinearities are developed. Results from the FE mathematical model are verified with results from the ANSYS computer program as well as with the test results. Sensitivity and feasibility studies are carried out. Significant geometry and force related variables are introduced;and by varying the geometric variables of the connections within a practical range, a matrix of test cases is obtained. Maximum end-plate separation, maximum bending stresses in the end-plate, and the forces from the connection bolts for these test cases are obtained. From the FE analysis, a database is produced to collect results for the artificial neural network analysis. Finally, salient features of the optimized Artificial Neural Network (ANN) via Genetic Algorithm (GA) analysis are introduced and implemented with the aim of predicting the overall behavior of the connection.展开更多
Different sets of dry spell length such as complete series, monthlymaximum, seasonal maximum, and annual maximum are applied andmodeled with different probability distribution functions (such as GumbelMax, generalized...Different sets of dry spell length such as complete series, monthlymaximum, seasonal maximum, and annual maximum are applied andmodeled with different probability distribution functions (such as GumbelMax, generalized extreme value, Log-Logistic, generalized logistic, inverseGaussian, Log-Pearson 3, generalized Pareto) to recognize in whichduration, dry spells cause drought. The drought situation and temporalanalysis in the North of Iraq region were done using the SPI index andby software of DrinC at a time scale of 3.6 and 12 months. Because ofapplicability, availability of data and the aim of the study, SPI is selectedto analyze the dry spells in this study. Based on the maximum length ofthe available statistical period, the statistics for the years 1980 to 2019were used from nine meteorological stations for analysis. The results of thestudy showed the severity of drought during the study period which relatedto dry spells. The results of this research confirm the variation of droughtoccurrence with varying degrees in different time and different dry spellscondition in Iraq.展开更多
Due to the interesting properties of hafnium diboride(HfB_2) as a ceramic, it has drawn considerabl attention from several researchers. To understand th radiation properties of HfB_2 that may be used in the nuclea ind...Due to the interesting properties of hafnium diboride(HfB_2) as a ceramic, it has drawn considerabl attention from several researchers. To understand th radiation properties of HfB_2 that may be used in the nuclea industry, the interaction of this composite under neutro irradiation was studied. It is obvious that, because HfB_2 ha Boron, this composite has the potential to absorb neutron particularly in the range of thermal energy. The ^(10)B(n, a7 Li interaction is dominant among other interactions tha produce alpha particles. The results revealed that alph particles have a high fluctuation diagram following a saw tooth spectrum for thermal neutron energy, which has to b carefully analyzed. If HfB_2 is intended to be used in fusio facilities, for example in fusion reactors, its interactio with high neutrons(14 Me V) should be studied. Th results of this case showed that, in the wide range of alph energy, the amount of alpha particles is almost constant, s this continuum spectrum is almost flat and there is just small peak at 2.31 Me V that belongs to the very famou interaction [^(10)B(n, a)~7Li].展开更多
Initial estimation is a considerable issue in channel estimation techniques, since all of the following processes depends on it, which in this paper its improvement is discussed. Least Square (LS) method is a common s...Initial estimation is a considerable issue in channel estimation techniques, since all of the following processes depends on it, which in this paper its improvement is discussed. Least Square (LS) method is a common simple way to estimate a channel initially but its efficiency is not as significant as more complex approaches. It is possible to enhance channel estimation performance by using some methods such as principal component analysis (PCA), which is not prevalent in channel estimation, and its adaptation to channel information can be challenging. PCA method improves initial estimation performance by projecting data onto direction of eigenvectors by means of using simple algebra. In this paper, channel estimation is examined in Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing (MIMO-OFDM) system, with significant advantages such as an acceptable performance in frequency selective fading channel. Moreover the proposed channel estimation method manipulates the benefits of MIMO channel by using the information, gained by all channels to estimate the information of each receiver.展开更多
文摘Considering snowmelt in mountainous areas as the important source of streamflow,the snow accumulation/melting processes are vital for accurate simulation of the hydrological regimes.The lack of snow-related data and its uncertainties/conceptual ambiguity in snowpack modeling are the different challenges of developing hydroclimatological models.To tackle these challenges,Global Gridded Snow Products(GGSPs)are introduced,which effectively simplify the identification of the spatial characteristics of snow hydrological variables.This research aims to investigate the performance of multisource GGSPs using multi-stage calibration strategies in hydrological modeling.The used GGSPs were Snow-Covered Area(SCA)and Snow Water Equivalent(SWE),implemented individually or jointly to calibrate an appropriate water balance model.The study area was a mountainous watershed located in Western Iran with a considerable contribution of snowmelt to the generated streamflow.The results showed that using GGSPs as complementary information in the calibration process,besides streamflow time series,could improve the modeling accuracy compared to the conventional calibration,which is only based on streamflow data.The SCA with NSE,KGE,and RMSE values varying within the ranges of 0.47–0.57,0.54–0.65,and 4–6.88,respectively,outperformed the SWE with the corresponding metrics of 0.36–0.59,0.47–0.60,and 5.22–7.46,respectively,in simulating the total streamflow of the watershed.In addition to the superiority of the SCA over SWE,the twostage calibration strategy reduced the number of optimized parameters in each stage and the dependency of internal processes on the streamflow and improved the accuracy of the results compared with the conventional calibration strategy.On the other hand,the consistent contribution of snowmelt to the total generated streamflow(ranging from 0.9 to 1.47)and the ratio of snow melting to snowfall(ranging from 0.925 to 1.041)in different calibration strategies and models resulted in a reliable simulation of the
文摘Fundamental characteristics of the plastic-scintillating fiber (PSF) for wide energy range of electromag- netic radiation (X & γ) have been studied to evaluate possibility of using the PSF as an imaging detector for industrial purposes. Monte-Carlo simulation program (GEANT4.5.1, 2003) was used to generate the data. In order to evaluate image quality of the detector, fiber array was irradiated under various energy and fluxes. Signal to noise ratio (SNR) as well as detector quantum efficiency (DQE) were obtained.
文摘Fundamental characteristics of the plastic scintillating fiber (PSF) as a detector for electromagnetic radiation (X & γ) are obtained by GEANT4 detector simulation tool package. The detector response to radiation with energy of 10~400 keV is found out. Energy deposition as well as detector efficiency (DE) of the PSF are studied. In order to make linear array of the PSF for imaging purpose, the optimum length of fiber is also estimated.
文摘AIM To assess the association of inter-ethnic vs intra-ethnic marriage with severity of coronary artery disease(CAD) in men undergoing angiography.METHODS We conducted a prospective multicenter,multi-ethnic,cross sectional observational study at five hospitals in Saudi Arabia and the United Arab Emirates,in which we used logistic regression analysis with and without adjustment for baseline differences. RESULTS Data were collected for 1068 enrolled patients undergoing coronary angiography for clinical indications during the period of April 1^(st),2013 to March 30^(th),2014. Ethnicities of spouses were available only for male patients. Of those enrolled,687 were married men and constituted the cohort for the present analysis. Intra-ethnic marriages were reported in 70% and inter-ethnic marriages in 30%. After adjusting for baseline differences,interethnic marriage was associated with lower odds of having significant CAD [adjusted odds ratio 0.52(95%CI:0.33,0.81)] or multi-vessel disease(MVD) [adjusted odds ratio 0.57(95%CI:0.37,0.86)]. The adjusted association with left main disease showed a similar trend,but was not statistically significant [adjusted odds ratio 0.74(95%CI:0.41,1.32)]. The association between interethnic marriage and the presence of significant CAD and MVD was not modified by number of concurrent wives(P interaction > 0.05 for both).CONCLUSION Among married men undergoing coronary angiography,inter-ethnic,as compared to intra-ethnic,marriage is associated with lower odds of significant CAD and MVD.
文摘AIM：To evaluate and compare structural optical coherence tomography（OCT）-based parameters,such as Bruch’s membrane opening-minimum rim width（BMO-MRW）,and retinal nerve fiber layer（RNFL）thickness in glaucoma patients with visual field（VF）defects,and to correlate both to mean deviation（MD）values of obtained standard achromatic perimetry（SAP）examinations.METHODS：Patients with glaucoma and glaucomatous VF defects were enrolled in this prospective study and compared to age-matched healthy individuals.All study participants underwent a full ophthalmic examination and VF testing with SAP.Peripapillary RNFL thickness and BMO-MRW were acquired with SD-OCT.Correlation analyses between obtained global functional and global as well as sectorial structural parameters were calculated.RESULTS：A consecutive series of 30 glaucomatous right eyes of 30 patients were included and compared to 36healthy right eyes of 36 individuals in the control group.Global MD of values correlated significantly with global RNFL（Pearson corr.coeff：0.632,P=0.001）and global BMO-MRW（Pearson corr.coeff：0.746,P〈0.001）values in the glaucoma group.Global MD and sectorial RNFL or BMO-MRW values correlated less significantly.In the control group,MD values did not correlate with RNFL or BMO-MRW measurements.A subgroup analysis of myopic patients（〉4 diopters）within the glaucoma group（n=6）revealed a tendency for higher correlations between MD and BMO-MRW than MD and RNFL measurements.CONCLUSION：In a clinical setting,RNFL thickness and BMO-MRW correlate similarly with global VF sensitivity in glaucoma patients with BMO-MRW showing higher correlations in myopic glaucoma patients.
基金Supported by a grant from the Zanjan University of Medical Sciences Vice chancellor for research(No.ZUMS.REC.1392.40)。
文摘OBJECTIVE: To compare the efficacy of honey mouthwash 12.5% and chlorhexidine solution 0.2%to reduce the rate of oropharyngeal bacterial colonization in mechanically-ventilated patients.METHODS: This study was a randomized, single blind, phase Ⅲ controlled clinical trial. Sixty patients newly admitted to internal and trauma Intensive Care Units of the two educational hospitals of Sanandaj city affiliated with Kurdistan University of Medical Sciences were selected by convenience sampling and allocated to two groups of 30 patients using random blocks design. In each group,the mouthwash was applied twice a day for four consecutive days. Swab samples were taken from the mouth and throat of all patients three times a day(pre-intervention, two days, and four days after the intervention) and then the samples were transferred onto the blood agar and eosin methylene blue(EMB) culture plates and investigated for bacterial growth and colonization after 24-48 h.RESULTS: The findings showed that oropharyngeal colonization was not significantly different between the two groups, pre-intervention, two days,and four days after the intervention(P > 0.05). Rinsing with honey mouthwash 12.5% led to the inhibition of Staphylococcus aureus and Pseudomonas aeruginosa on the fourth day of the intervention in all samples.CONCLUSION: None of the studied solutions contributed to the reduction of oropharyngeal bacterial colonization. It seems that the growth inhibition of Staphylococcus aureus and Pseudomonas aeruginosa by the honey 12.5% mouthwash in mechanically-ventilated patients need further investigation.
文摘It is important to assess image quality, in order to ensure that the imaging system is performing optimally and also identify the weak points in an imaging system. Three parameters mostly leading to image degradation are contrast, spatial resolution and noise. There is always a trade-off between spatial resolution and signal to noise ratio, but in scintillating fiber array detectors spatial resolution is not as important as signal to noise ratio, so we paid more attention to contrast and SNR of the system. By using GEANT4 Monte Carlo detector simulation toolkit, some effec- tive parameters of the linear plastic scintillating fiber (PSF) array as an imaging detector were investigated. Finally we show that it is possible to use this kind of detector to take CT and DR (Digital Radiography) image under certain conditions.
文摘Water quality and occurrence of water-borne diseases in the Gaza strip are vivid examples for most developing societies. In recent years, the quality and quantity of groundwater, the only source of waters in the Gaza strip, have deteriorated markedly. A general rundown of the infrastructure and water distribution networks, in particular, the spread of cesspools, excessive use of pesticides and fertilizers, and improper treatment and disposal of wastewater remain major contributing factors to the continued deterioration in the water status in the Gaza strip. Without a doubt, the (Israeli)-Palestinian conflict had a clear negative impact on the water sector in the Gaza strip. Apparently, there is a dire need to adopt the WHO’s water safety plan in the management of Gaza’s water supply systems from catchment to consumer’s tap in order to maintain the sustainability and quality of water resources and prevent outbreaks of waterborne diseases. Therefore, this review has been prepared to highlight the overall picture of the water dilemma in the Gaza strip in the last years and in addition, to identify the sources, sorts, levels, and health risks of consequence to microbial contamination of water. The impact of political conflicts on the water sector in the Gaza strip also was reviewed. Furthermore, recommendations were formulated in order to assist and guide future researchers, stakeholders, and policymakers to avoid the more exacerbation of water contamination as well as to protect public health.
文摘One-dimensional （1D） catalytic etching was investigated in few-layer hexagonal boron nitride （hBN） films. Etching of hBN was shown to share a number of similarities with that of graphitic films. As in graphitic films, etch tracks in hBN commenced at film edges and occurred predominantly along certain crystal directions of its lattice, though it was shown that the tracks were generally narrower than those of few-layer graphene under similar processing conditions. It was also shown that catalytic hydrogenation can occur completely through a few-layer hBN film, demonstrating that this process can be used in the formation of isolated low-dimensional nanoscale structures from other layered 2D materials beyond graphene. This ability for thin hBN films to be etched completely through allowed for a crystalline substrate to guide the etching process, which was demonstrated with the successful etch track formation of few-layer hBN on single-crystalline sapphire substrates. The substrate-guided etching resulted in parallel few-layer hBN nanoribbons having an average width of 32 nm and spacing of 13 nm.
文摘This study involves the development of an analytical model for understanding the behavior of the extended, stiffened end-plate moment connections with eight high strength bolts. Modeling of the connection as an assemblage of finite elements (FE) used for load deformation analysis, with material, and contact nonlinearities are developed. Results from the FE mathematical model are verified with results from the ANSYS computer program as well as with the test results. Sensitivity and feasibility studies are carried out. Significant geometry and force related variables are introduced;and by varying the geometric variables of the connections within a practical range, a matrix of test cases is obtained. Maximum end-plate separation, maximum bending stresses in the end-plate, and the forces from the connection bolts for these test cases are obtained. From the FE analysis, a database is produced to collect results for the artificial neural network analysis. Finally, salient features of the optimized Artificial Neural Network (ANN) via Genetic Algorithm (GA) analysis are introduced and implemented with the aim of predicting the overall behavior of the connection.
文摘Different sets of dry spell length such as complete series, monthlymaximum, seasonal maximum, and annual maximum are applied andmodeled with different probability distribution functions (such as GumbelMax, generalized extreme value, Log-Logistic, generalized logistic, inverseGaussian, Log-Pearson 3, generalized Pareto) to recognize in whichduration, dry spells cause drought. The drought situation and temporalanalysis in the North of Iraq region were done using the SPI index andby software of DrinC at a time scale of 3.6 and 12 months. Because ofapplicability, availability of data and the aim of the study, SPI is selectedto analyze the dry spells in this study. Based on the maximum length ofthe available statistical period, the statistics for the years 1980 to 2019were used from nine meteorological stations for analysis. The results of thestudy showed the severity of drought during the study period which relatedto dry spells. The results of this research confirm the variation of droughtoccurrence with varying degrees in different time and different dry spellscondition in Iraq.
基金supported by the School of Plasma Physics and Nuclear Fusion, Institute of Nuclear Science and Technology (AEOI)
文摘Due to the interesting properties of hafnium diboride(HfB_2) as a ceramic, it has drawn considerabl attention from several researchers. To understand th radiation properties of HfB_2 that may be used in the nuclea industry, the interaction of this composite under neutro irradiation was studied. It is obvious that, because HfB_2 ha Boron, this composite has the potential to absorb neutron particularly in the range of thermal energy. The ^(10)B(n, a7 Li interaction is dominant among other interactions tha produce alpha particles. The results revealed that alph particles have a high fluctuation diagram following a saw tooth spectrum for thermal neutron energy, which has to b carefully analyzed. If HfB_2 is intended to be used in fusio facilities, for example in fusion reactors, its interactio with high neutrons(14 Me V) should be studied. Th results of this case showed that, in the wide range of alph energy, the amount of alpha particles is almost constant, s this continuum spectrum is almost flat and there is just small peak at 2.31 Me V that belongs to the very famou interaction [^(10)B(n, a)~7Li].
文摘Initial estimation is a considerable issue in channel estimation techniques, since all of the following processes depends on it, which in this paper its improvement is discussed. Least Square (LS) method is a common simple way to estimate a channel initially but its efficiency is not as significant as more complex approaches. It is possible to enhance channel estimation performance by using some methods such as principal component analysis (PCA), which is not prevalent in channel estimation, and its adaptation to channel information can be challenging. PCA method improves initial estimation performance by projecting data onto direction of eigenvectors by means of using simple algebra. In this paper, channel estimation is examined in Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing (MIMO-OFDM) system, with significant advantages such as an acceptable performance in frequency selective fading channel. Moreover the proposed channel estimation method manipulates the benefits of MIMO channel by using the information, gained by all channels to estimate the information of each receiver.
