In this paper, we define the Weibull kernel and use it to nonparametric estimation of the probability density function (pdf) and the hazard rate function for independent and identically distributed (iid) data. The bia...In this paper, we define the Weibull kernel and use it to nonparametric estimation of the probability density function (pdf) and the hazard rate function for independent and identically distributed (iid) data. The bias, variance and the optimal bandwidth of the proposed estimator are investigated. Moreover, the asymptotic normality of the proposed estimator is investigated. The performance of the proposed estimator is tested using simulation study and real data.展开更多
We model an epidemic with a class of nonhomogeneous Markov chains on the supercritical percolation network on Zd. The large deviations law for the Markov chain is given. Explicit expression of the rate function for la...We model an epidemic with a class of nonhomogeneous Markov chains on the supercritical percolation network on Zd. The large deviations law for the Markov chain is given. Explicit expression of the rate function for large deviation is obtained.展开更多
This is a sequel to our joint paper in which upper bound estimates for large deviations for Markov chains are studied.The purpose of this paper is to characterize the rate function of large devia- tions for jump proce...This is a sequel to our joint paper in which upper bound estimates for large deviations for Markov chains are studied.The purpose of this paper is to characterize the rate function of large devia- tions for jump processes.In particular,an explicit expression of the rate function is given in the case of the process being symmetrizable.展开更多
AIM: To evaluate the usefulness of the functional hepatic resection rate (FHRR) calculated using 3D computed tomography (CT)/<sup>99m</sup>Tc-galactosyl-human serum albumin (GSA) single-photon emission com...AIM: To evaluate the usefulness of the functional hepatic resection rate (FHRR) calculated using 3D computed tomography (CT)/<sup>99m</sup>Tc-galactosyl-human serum albumin (GSA) single-photon emission computed tomography (SPECT) fusion imaging for surgical decision making.METHODS: We enrolled 57 patients who underwent bi- or trisectionectomy at our institution between October 2013 and March 2015. Of these, 26 patients presented with hepatocellular carcinoma, 12 with hilar cholangiocarcinoma, six with intrahepatic cholangiocarcinoma, four with liver metastasis, and nine with other diseases. All patients preoperatively underwent three-phase dynamic multidetector CT and <sup>99m</sup>Tc-GSA scintigraphy. We compared the parenchymal hepatic resection rate (PHRR) with the FHRR, which was defined as the resection volume counts per total liver volume counts on 3D CT/<sup>99m</sup>Tc-GSA SPECT fusion images.RESULTS: In total, 50 patients underwent bisectionectomy and seven underwent trisectionectomy. Biliary reconstruction was performed in 15 patients, including hepatopancreatoduodenectomy in two. FHRR and PHRR were 38.6 ± 19.9 and 44.5 ± 16.0, respectively; FHRR was strongly correlated with PHRR. The regression coefficient for FHRR on PHRR was 1.16 (P < 0.0001). The ratio of FHRR to PHRR for patients with preoperative therapies (transcatheter arterial chemoembolization, radiation, radiofrequency ablation, etc.), large tumors with a volume of > 1000 mL, and/or macroscopic vascular invasion was significantly smaller than that for patients without these factors (0.73 ± 0.19 vs 0.82 ± 0.18, P < 0.05). Postoperative hyperbilirubinemia was observed in six patients. Major morbidities (Clavien-Dindo grade ≥ 3) occurred in 17 patients (29.8%). There was no case of surgery-related death.CONCLUSION: Our results suggest that FHRR is an important deciding factor for major hepatectomy, because FHRR and PHRR may be discrepant owing to insufficient hepatic inflow and congestion in patients with preoperative therapies, macroscopic vascular invasion, and/or a tumor volume of > 1000 mL.展开更多
When the rate of a symmetric second-order symmetric tensor is discussed,the spin of the principal axis is involved.This paper proposes a method to establish the basis-free expression of the spin in terms of tensor and...When the rate of a symmetric second-order symmetric tensor is discussed,the spin of the principal axis is involved.This paper proposes a method to establish the basis-free expression of the spin in terms of tensor and its rate by making use of the tensor function representation theorem.The proposed method is simple and the expression of the spin established is compact.To obtain the rate of the isotropic function of a second-order symmetric tensor,the fourth-order tangent tensor needs to be derived,which is the derivative of the tensor function to the second-order tensor.By decomposing the second-order symmetric tensor space into two orthogonal subspaces,the closed-form fourth-order tangent tensor is decomposed into two parts,which are linear mappings in these two orthogonal subspaces,respectively.These two linear mappings are derived in an extremely simple way.Finally,the method proposed in this paper is applied to obtain the expression of the relationship between material logarithmic strain rate and deformation rate.The whole process is simple and avoids tedious operations.展开更多
The total power rate functional for hot rolling problem with the rigid-plastic SCM model is considered. The gradient operator of the plastic deformation power rate functional is deduced. it is strictly monotone mappin...The total power rate functional for hot rolling problem with the rigid-plastic SCM model is considered. The gradient operator of the plastic deformation power rate functional is deduced. it is strictly monotone mapping. Further, it is proved that the frictional power rate functional is a convex functional and the tensional stress power rate functional is a linear one. Hence, the total power rate functional is a strictly convex functional. By using nonlinear functional analysis methods, the existence and uniqueness of extreme point of the functional is obtained.展开更多
Introduction: Tc-99m Di-ethylene Tri-amine Penta Acetic Acid (DTPA) renogram is an accepted method to measure Glomerular Filtration Rate (GFR) of the kidneys. The depth and position of ectopic kidneys may vary. This m...Introduction: Tc-99m Di-ethylene Tri-amine Penta Acetic Acid (DTPA) renogram is an accepted method to measure Glomerular Filtration Rate (GFR) of the kidneys. The depth and position of ectopic kidneys may vary. This may lead to variation in tissue attenuation and error in the computed GFR and Differential Renal Function (DRF) of each kidney. Objective: The present study was undertaken in patients with ectopic kidneys to improve the accuracy of GFR and DRF calculation in a renogram with single injection of Tc-99m DTPA on a dual head gamma camera. Materials and Method: The study was conducted on 55 patients with ectopic kidneys. Images were acquired on a dual head gamma camera simultaneously in anterior and posterior views. Both anterior and posterior image datasets were used to compute the GFR of the ectopic kidney by Gates method. Depth correction of the ectopic kidney was done using the lateral view image. Total GFR was calculated as the sum of the anterior dataset ectopic kidney GFR and the posterior dataset normal kidney GFR. DRF was calculated again, by using the anterior dataset GFR of the ectopic kidney and posterior dataset for normal kidneys. The total GFR calculated by our method was compared to the patient’s eGFR (based on serum creatinine, age and sex). Result: The GFR calculated by anterior data set in the ectopic kidney was significantly higher than that calculated by posterior dataset (p 0.001). Similarly, the differential GFR of the ectopic kidney was higher when the anterior dataset was used (p 0.001). The ectopic kidney GFR of 34 (61.8%) of the 55 patients was greater than 35 ml/min, whereas in 21 patients (38.2%), it was less than 35 ml/min. The total GFR calculated by using both anterior and posterior data set was compared with the eGFR;the correlation coefficient was 0.74 in patients with ectopic kidney GFR of >35 ml/min and 0.83 in those with Conclusion: The GFR of ectopic kidney as calculated from the anterior data set was significantly higher in comparison to the GFR calculated from the posterior data set (p 0.001). Using the anterior dataset GFR, the DRF values for the ectopic kidneys was also significantly higher (p 0.001). This method improves the accuracy of the GFR and DRF values and helps to differentiate a normally functioning ectopic kidney from a poorly functioning one. Compared to the total GFR as calculated by the present method, the eGFR showed a better correlation in patients with ectopic kidney展开更多
In this paper, we study the strong consistency and convergence rate for modified partitioning estimation of regression function under samples that are ψ-mixing with identically distribution.
Since the room-temperature detector CdZnTe(CZT) has advantages in terms of detection efficiency,energy resolution, and size, it has been extensively used to detect X-rays and gamma-rays. So far, nuclear radiation dete...Since the room-temperature detector CdZnTe(CZT) has advantages in terms of detection efficiency,energy resolution, and size, it has been extensively used to detect X-rays and gamma-rays. So far, nuclear radiation detectors such as cerium chloride doped with lanthanum bromide(LaBr_3(Ce)), thallium doped with cesium iodide(sI(Tl)), thallium doped with sodium iodide(NaI(Tl)),and high-purity germanium(HPGe) primarily use the spectroscopy-dose rate function(G(E)) to achieve the accurate measurement of air kerma rate(K_a) and ambient dose equivalent rate(H*(10)). However, the spectroscopy-dose rate function has been rarely measured for a CZT detector. In this study, we performed spectrum measurement using a hemispherical CZT detector in a radiation protection standards laboratory. The spectroscopy-dose rate function G(E) of the CZT detector was calculated using the least-squares method combined with the standard dose rate at the measurement position. The results showed that the hemispherical CZT detector could complete the measurement of air kerma rate(K_a) and ambient dose equivalent rate(H*(10)) by using the G(E) function at energies between 48 keV and 1.25 MeV, and the relative intrinsic errors were, respectively, controlled within ± 2. 3 and ± 2. 1%.展开更多
Objective To study the validation of ultrasound-based strain rate imaging in the quantitative assessment of right ventricular （RV） function in atrial septal defect （ASD）. Methods Tissue Doppler images （TDI） of R...Objective To study the validation of ultrasound-based strain rate imaging in the quantitative assessment of right ventricular （RV） function in atrial septal defect （ASD）. Methods Tissue Doppler images （TDI） of RV longitudinal and short axes were recorded from the apical 4-chamber view and the subcostal short-axis view in 18 normal controls, 28 children with ASD and 14 children after Amplazter closure of ASD respectively. Peak systolic velocities （ V）, peak systolic strain rates （SR）, peak systolic strains （S） at the basal segment, middle segment of RV lateral wall and the basal septum from the longitudinal axis, the middle segment of RV free waU from the short axis were quantitatively measured using QLAB^TM tissue velocity quantification software system respectively. Peak dp/ dt from the RV isovolumic contraction determined during the right cardiac catheterization in 28 ASD patients was used as the gold standard of RV contractility. Peak systolic indices were compared against max dp/dt by linear correlation, Results Peak systolic indices at the basal and middle segments of RV lateral wall from the longitudiual axis increased significantly in 28 ASD patients. Peak systolic indices at the basal septum also increased in patient group, but not significantly. Significant decreases in peak systolic indices at the basal and middle segments of RV lateral wall were observed after the Amplatzer closure in 14 ASD patients. There was no significant difference at the middle segment of RV free wall from the short axis between patient group and normal control. A strong correlation was found between max dp/dt and peak systolic indices at the basal and middle segments of RV lateral wal l （ P 〈 0. 05 ）. Conclusion Ultrasound-based strain rate imaging can assess quantitatively RVfunction in CHD. Peak systolic strains determined at the basal and middle segments of RV lateral wall are strong noninvasive indices of RV contractility.展开更多
Introduction: Coronary artery disease (CAD) is the most common cause for left ventricular dysfunction. Unfortunately, the treatment strategies of regional myocardial diastolic dysfunction in patients with CAD have not...Introduction: Coronary artery disease (CAD) is the most common cause for left ventricular dysfunction. Unfortunately, the treatment strategies of regional myocardial diastolic dysfunction in patients with CAD have not been well characterized and benefit of percutaneous coronary intervention (PCI) as a treatment strategy is not clear. So the present study aimed to assess the effects of PCI on regional and global left ventricular diastolic dysfunction in patients with CAD assessed by strain rate (SR) imaging. Methods: Thirty adult symptomatic patients with coronary artery disease that underwent coronary angiography and candidate for PCI on left anterior descending artery were enrolled to our study. Echocardiographic findings and early diastolic SR were measured before and 48 hours after PCI. Results: Mean age of the patients was 59.9 ± 8.3 years. Most of the left ventricular diastolic parameters showed significant difference before and after elective PCI;while mitral E velocity, DT, E/A and pulmonary vein flow before and after PCI did not show significant difference assessed by statically test. Also before PCI, mean (SD) of peak early diastolic SR in ischemic regions (1.89 ± 0.22) was smaller than of non-ischemic regions (2.53 ± 0.26) while after PCI this parameter became similar in ischemic regions (2.55 ± 0.27) and non-ischemic regions (2.55 ± 0.26). Conclusion: Most of the left ventricular diastolic parameters improved after PCI in CAD patients. Also regional myocardial relaxation as measured by peak early diastolic SR (ESR) in the ischemic segments improved significantly compared with that in non-ischemic segments.展开更多
This paper deals with a Unit Commitment (UC) problem of a power plant aimed to find the optimal scheduling of the generating units involving cubic cost functions. The problem has non convex generator characteristics, ...This paper deals with a Unit Commitment (UC) problem of a power plant aimed to find the optimal scheduling of the generating units involving cubic cost functions. The problem has non convex generator characteristics, which makes it very hard to handle the corresponding mathematical models. However, Teaching Learning Based Optimization (TLBO) has reached a high efficiency, in terms of solution accuracy and computing time for such non convex problems. Hence, TLBO is applied for scheduling of generators with higher order cost characteristics, and turns out to be computationally solvable. In particular, we represent a model that takes into account the accurate higher order generator cost functions along with ramp limits, and turns to be more general and efficient than those available in the literature. The behavior of the model is analyzed through proposed technique on modified IEEE-24 bus system.展开更多
Present paper deals a M/M/1:(∞;GD) queueing model with interdependent controllable arrival and service rates where- in customers arrive in the system according to poisson distribution with two different arrivals rate...Present paper deals a M/M/1:(∞;GD) queueing model with interdependent controllable arrival and service rates where- in customers arrive in the system according to poisson distribution with two different arrivals rates-slower and faster as per controllable arrival policy. Keeping in view the general trend of interdependent arrival and service processes, it is presumed that random variables of arrival and service processes follow a bivariate poisson distribution and the server provides his services under general discipline of service rule in an infinitely large waiting space. In this paper, our central attention is to explore the probability generating functions using Rouche’s theorem in both cases of slower and faster arrival rates of the queueing model taken into consideration;which may be helpful for mathematicians and researchers for establishing significant performance measures of the model. Moreover, for the purpose of high-lighting the application aspect of our investigated result, very recently Maurya [1] has derived successfully the expected busy periods of the server in both cases of slower and faster arrival rates, which have also been presented by the end of this paper.展开更多
This paper presents an improved BP algorithm. The approach can reduce the amount of computation by using the logarithmic objective function. The learning rate μ(k) per iteration is determined by dynamic o...This paper presents an improved BP algorithm. The approach can reduce the amount of computation by using the logarithmic objective function. The learning rate μ(k) per iteration is determined by dynamic optimization method to accelerate the convergence rate. Since the determination of the learning rate in the proposed BP algorithm only uses the obtained first order derivatives in standard BP algorithm(SBP), the scale of computational and storage burden is like that of SBP algorithm,and the convergence rate is remarkably accelerated. Computer simulations demonstrate the effectiveness of the proposed algorithm展开更多
Objectives To detect and compare the systolic strain rate (SR) and strain in the infarct and ischemic myocardium by strain rate imaging (SRI), in order to explore the clinical value of SRI in evaluating regional left ...Objectives To detect and compare the systolic strain rate (SR) and strain in the infarct and ischemic myocardium by strain rate imaging (SRI), in order to explore the clinical value of SRI in evaluating regional left ventricular systolic dysfunction. Methods Patients with coronary artery disease were divided into angina pectoris (11 cases) and myocardial infarction (21 cases) groups. Twenty age-matched normal subjects served as the control group. Septal, lateral, anterior, inferior, anteroseptal and posterior walls of the left ventricle were respectively scanned using color tissue Doppler imaging (TDI). Then SR and strain curves were derived from TDI for basal, middle and apical segments of each wall. SRI parameters were: Systolic SR (SRsys), systolic strain (εsys) and maximum strain (εmax). Results Compared with normal segments, SRsys, εsys and εmax decreased significantly in the infarct and ischemic segments (P<0.01). Compared with ischemic segments, SRsys, εsys and εmax decreased significantly in the infarct segments (P<0.05). Conclusions SRsys, εsys and εmax measured by SRI can be used to quantitatively analyze regional left ventricular systolic dysfunction in patients with coronary artery disease, and aid in differentiating infarct from ischemic myocardium.展开更多
A new method of the multiple rates isotemperature is proposed to define the most probable mechanismg(α) of thermal anlaysis; the iterative isoconversional procedure has been employed to estimate apparent activation e...A new method of the multiple rates isotemperature is proposed to define the most probable mechanismg(α) of thermal anlaysis; the iterative isoconversional procedure has been employed to estimate apparent activation energyE; the pre-exponential factorA is obtained on the basis ofE andg(α). By this new method, the thermal analysis kinetics triplet of dehydration of cobalt oxalate dihydrate is determined, apparent activation energyE is 99.84 kJ·mol?1; pre-exponential factorA is 3.427×109–3.872×109 s?1 and the most probable mechanism belongs to nucleation and growth,A m model, the range ofm is from 1.50 to 1.70. Key words multiple rates isotemperature method - isoconversional method - cobalt oxalate dihydrate - accomodation function - differential scanning calorimetry (DSC) CLC number O 636.1 Foundation item: Supported by the Key Foundation of the Science and Technology Committee of Hubei Province (2001ABA009)Biography: Li Li-qing (1977-), female, Master candidate, research direction: material synthesize and thermal analysis kinetics.展开更多
文摘In this paper, we define the Weibull kernel and use it to nonparametric estimation of the probability density function (pdf) and the hazard rate function for independent and identically distributed (iid) data. The bias, variance and the optimal bandwidth of the proposed estimator are investigated. Moreover, the asymptotic normality of the proposed estimator is investigated. The performance of the proposed estimator is tested using simulation study and real data.
基金Supported by Mathematical Tianyuan Foundation （Grant No. 10926117） and National Natural Science Foundation of China （Grant No. 10531070） The authors would like to thank the referee for having read the paper carefully and for suggesting arrangements of article structure.
文摘We model an epidemic with a class of nonhomogeneous Markov chains on the supercritical percolation network on Zd. The large deviations law for the Markov chain is given. Explicit expression of the rate function for large deviation is obtained.
文摘This is a sequel to our joint paper in which upper bound estimates for large deviations for Markov chains are studied.The purpose of this paper is to characterize the rate function of large devia- tions for jump processes.In particular,an explicit expression of the rate function is given in the case of the process being symmetrizable.
文摘AIM: To evaluate the usefulness of the functional hepatic resection rate (FHRR) calculated using 3D computed tomography (CT)/<sup>99m</sup>Tc-galactosyl-human serum albumin (GSA) single-photon emission computed tomography (SPECT) fusion imaging for surgical decision making.METHODS: We enrolled 57 patients who underwent bi- or trisectionectomy at our institution between October 2013 and March 2015. Of these, 26 patients presented with hepatocellular carcinoma, 12 with hilar cholangiocarcinoma, six with intrahepatic cholangiocarcinoma, four with liver metastasis, and nine with other diseases. All patients preoperatively underwent three-phase dynamic multidetector CT and <sup>99m</sup>Tc-GSA scintigraphy. We compared the parenchymal hepatic resection rate (PHRR) with the FHRR, which was defined as the resection volume counts per total liver volume counts on 3D CT/<sup>99m</sup>Tc-GSA SPECT fusion images.RESULTS: In total, 50 patients underwent bisectionectomy and seven underwent trisectionectomy. Biliary reconstruction was performed in 15 patients, including hepatopancreatoduodenectomy in two. FHRR and PHRR were 38.6 ± 19.9 and 44.5 ± 16.0, respectively; FHRR was strongly correlated with PHRR. The regression coefficient for FHRR on PHRR was 1.16 (P < 0.0001). The ratio of FHRR to PHRR for patients with preoperative therapies (transcatheter arterial chemoembolization, radiation, radiofrequency ablation, etc.), large tumors with a volume of > 1000 mL, and/or macroscopic vascular invasion was significantly smaller than that for patients without these factors (0.73 ± 0.19 vs 0.82 ± 0.18, P < 0.05). Postoperative hyperbilirubinemia was observed in six patients. Major morbidities (Clavien-Dindo grade ≥ 3) occurred in 17 patients (29.8%). There was no case of surgery-related death.CONCLUSION: Our results suggest that FHRR is an important deciding factor for major hepatectomy, because FHRR and PHRR may be discrepant owing to insufficient hepatic inflow and congestion in patients with preoperative therapies, macroscopic vascular invasion, and/or a tumor volume of > 1000 mL.
文摘When the rate of a symmetric second-order symmetric tensor is discussed,the spin of the principal axis is involved.This paper proposes a method to establish the basis-free expression of the spin in terms of tensor and its rate by making use of the tensor function representation theorem.The proposed method is simple and the expression of the spin established is compact.To obtain the rate of the isotropic function of a second-order symmetric tensor,the fourth-order tangent tensor needs to be derived,which is the derivative of the tensor function to the second-order tensor.By decomposing the second-order symmetric tensor space into two orthogonal subspaces,the closed-form fourth-order tangent tensor is decomposed into two parts,which are linear mappings in these two orthogonal subspaces,respectively.These two linear mappings are derived in an extremely simple way.Finally,the method proposed in this paper is applied to obtain the expression of the relationship between material logarithmic strain rate and deformation rate.The whole process is simple and avoids tedious operations.
文摘The total power rate functional for hot rolling problem with the rigid-plastic SCM model is considered. The gradient operator of the plastic deformation power rate functional is deduced. it is strictly monotone mapping. Further, it is proved that the frictional power rate functional is a convex functional and the tensional stress power rate functional is a linear one. Hence, the total power rate functional is a strictly convex functional. By using nonlinear functional analysis methods, the existence and uniqueness of extreme point of the functional is obtained.
文摘Introduction: Tc-99m Di-ethylene Tri-amine Penta Acetic Acid (DTPA) renogram is an accepted method to measure Glomerular Filtration Rate (GFR) of the kidneys. The depth and position of ectopic kidneys may vary. This may lead to variation in tissue attenuation and error in the computed GFR and Differential Renal Function (DRF) of each kidney. Objective: The present study was undertaken in patients with ectopic kidneys to improve the accuracy of GFR and DRF calculation in a renogram with single injection of Tc-99m DTPA on a dual head gamma camera. Materials and Method: The study was conducted on 55 patients with ectopic kidneys. Images were acquired on a dual head gamma camera simultaneously in anterior and posterior views. Both anterior and posterior image datasets were used to compute the GFR of the ectopic kidney by Gates method. Depth correction of the ectopic kidney was done using the lateral view image. Total GFR was calculated as the sum of the anterior dataset ectopic kidney GFR and the posterior dataset normal kidney GFR. DRF was calculated again, by using the anterior dataset GFR of the ectopic kidney and posterior dataset for normal kidneys. The total GFR calculated by our method was compared to the patient’s eGFR (based on serum creatinine, age and sex). Result: The GFR calculated by anterior data set in the ectopic kidney was significantly higher than that calculated by posterior dataset (p 0.001). Similarly, the differential GFR of the ectopic kidney was higher when the anterior dataset was used (p 0.001). The ectopic kidney GFR of 34 (61.8%) of the 55 patients was greater than 35 ml/min, whereas in 21 patients (38.2%), it was less than 35 ml/min. The total GFR calculated by using both anterior and posterior data set was compared with the eGFR;the correlation coefficient was 0.74 in patients with ectopic kidney GFR of >35 ml/min and 0.83 in those with Conclusion: The GFR of ectopic kidney as calculated from the anterior data set was significantly higher in comparison to the GFR calculated from the posterior data set (p 0.001). Using the anterior dataset GFR, the DRF values for the ectopic kidneys was also significantly higher (p 0.001). This method improves the accuracy of the GFR and DRF values and helps to differentiate a normally functioning ectopic kidney from a poorly functioning one. Compared to the total GFR as calculated by the present method, the eGFR showed a better correlation in patients with ectopic kidney
基金The Science Research Fundation (041002F) of Hefei University of Technology.
文摘In this paper, we study the strong consistency and convergence rate for modified partitioning estimation of regression function under samples that are ψ-mixing with identically distribution.
基金supported by the National Key Scientific Instruments to Develop Dedicated(Nos.2013YQ090811 and 2016YFF0103800)
文摘Since the room-temperature detector CdZnTe(CZT) has advantages in terms of detection efficiency,energy resolution, and size, it has been extensively used to detect X-rays and gamma-rays. So far, nuclear radiation detectors such as cerium chloride doped with lanthanum bromide(LaBr_3(Ce)), thallium doped with cesium iodide(sI(Tl)), thallium doped with sodium iodide(NaI(Tl)),and high-purity germanium(HPGe) primarily use the spectroscopy-dose rate function(G(E)) to achieve the accurate measurement of air kerma rate(K_a) and ambient dose equivalent rate(H*(10)). However, the spectroscopy-dose rate function has been rarely measured for a CZT detector. In this study, we performed spectrum measurement using a hemispherical CZT detector in a radiation protection standards laboratory. The spectroscopy-dose rate function G(E) of the CZT detector was calculated using the least-squares method combined with the standard dose rate at the measurement position. The results showed that the hemispherical CZT detector could complete the measurement of air kerma rate(K_a) and ambient dose equivalent rate(H*(10)) by using the G(E) function at energies between 48 keV and 1.25 MeV, and the relative intrinsic errors were, respectively, controlled within ± 2. 3 and ± 2. 1%.
文摘Objective To study the validation of ultrasound-based strain rate imaging in the quantitative assessment of right ventricular （RV） function in atrial septal defect （ASD）. Methods Tissue Doppler images （TDI） of RV longitudinal and short axes were recorded from the apical 4-chamber view and the subcostal short-axis view in 18 normal controls, 28 children with ASD and 14 children after Amplazter closure of ASD respectively. Peak systolic velocities （ V）, peak systolic strain rates （SR）, peak systolic strains （S） at the basal segment, middle segment of RV lateral wall and the basal septum from the longitudinal axis, the middle segment of RV free waU from the short axis were quantitatively measured using QLAB^TM tissue velocity quantification software system respectively. Peak dp/ dt from the RV isovolumic contraction determined during the right cardiac catheterization in 28 ASD patients was used as the gold standard of RV contractility. Peak systolic indices were compared against max dp/dt by linear correlation, Results Peak systolic indices at the basal and middle segments of RV lateral wall from the longitudiual axis increased significantly in 28 ASD patients. Peak systolic indices at the basal septum also increased in patient group, but not significantly. Significant decreases in peak systolic indices at the basal and middle segments of RV lateral wall were observed after the Amplatzer closure in 14 ASD patients. There was no significant difference at the middle segment of RV free wall from the short axis between patient group and normal control. A strong correlation was found between max dp/dt and peak systolic indices at the basal and middle segments of RV lateral wal l （ P 〈 0. 05 ）. Conclusion Ultrasound-based strain rate imaging can assess quantitatively RVfunction in CHD. Peak systolic strains determined at the basal and middle segments of RV lateral wall are strong noninvasive indices of RV contractility.
文摘Introduction: Coronary artery disease (CAD) is the most common cause for left ventricular dysfunction. Unfortunately, the treatment strategies of regional myocardial diastolic dysfunction in patients with CAD have not been well characterized and benefit of percutaneous coronary intervention (PCI) as a treatment strategy is not clear. So the present study aimed to assess the effects of PCI on regional and global left ventricular diastolic dysfunction in patients with CAD assessed by strain rate (SR) imaging. Methods: Thirty adult symptomatic patients with coronary artery disease that underwent coronary angiography and candidate for PCI on left anterior descending artery were enrolled to our study. Echocardiographic findings and early diastolic SR were measured before and 48 hours after PCI. Results: Mean age of the patients was 59.9 ± 8.3 years. Most of the left ventricular diastolic parameters showed significant difference before and after elective PCI;while mitral E velocity, DT, E/A and pulmonary vein flow before and after PCI did not show significant difference assessed by statically test. Also before PCI, mean (SD) of peak early diastolic SR in ischemic regions (1.89 ± 0.22) was smaller than of non-ischemic regions (2.53 ± 0.26) while after PCI this parameter became similar in ischemic regions (2.55 ± 0.27) and non-ischemic regions (2.55 ± 0.26). Conclusion: Most of the left ventricular diastolic parameters improved after PCI in CAD patients. Also regional myocardial relaxation as measured by peak early diastolic SR (ESR) in the ischemic segments improved significantly compared with that in non-ischemic segments.
文摘This paper deals with a Unit Commitment (UC) problem of a power plant aimed to find the optimal scheduling of the generating units involving cubic cost functions. The problem has non convex generator characteristics, which makes it very hard to handle the corresponding mathematical models. However, Teaching Learning Based Optimization (TLBO) has reached a high efficiency, in terms of solution accuracy and computing time for such non convex problems. Hence, TLBO is applied for scheduling of generators with higher order cost characteristics, and turns out to be computationally solvable. In particular, we represent a model that takes into account the accurate higher order generator cost functions along with ramp limits, and turns to be more general and efficient than those available in the literature. The behavior of the model is analyzed through proposed technique on modified IEEE-24 bus system.
文摘Present paper deals a M/M/1:(∞;GD) queueing model with interdependent controllable arrival and service rates where- in customers arrive in the system according to poisson distribution with two different arrivals rates-slower and faster as per controllable arrival policy. Keeping in view the general trend of interdependent arrival and service processes, it is presumed that random variables of arrival and service processes follow a bivariate poisson distribution and the server provides his services under general discipline of service rule in an infinitely large waiting space. In this paper, our central attention is to explore the probability generating functions using Rouche’s theorem in both cases of slower and faster arrival rates of the queueing model taken into consideration;which may be helpful for mathematicians and researchers for establishing significant performance measures of the model. Moreover, for the purpose of high-lighting the application aspect of our investigated result, very recently Maurya [1] has derived successfully the expected busy periods of the server in both cases of slower and faster arrival rates, which have also been presented by the end of this paper.
文摘This paper presents an improved BP algorithm. The approach can reduce the amount of computation by using the logarithmic objective function. The learning rate μ(k) per iteration is determined by dynamic optimization method to accelerate the convergence rate. Since the determination of the learning rate in the proposed BP algorithm only uses the obtained first order derivatives in standard BP algorithm(SBP), the scale of computational and storage burden is like that of SBP algorithm,and the convergence rate is remarkably accelerated. Computer simulations demonstrate the effectiveness of the proposed algorithm
文摘Objectives To detect and compare the systolic strain rate (SR) and strain in the infarct and ischemic myocardium by strain rate imaging (SRI), in order to explore the clinical value of SRI in evaluating regional left ventricular systolic dysfunction. Methods Patients with coronary artery disease were divided into angina pectoris (11 cases) and myocardial infarction (21 cases) groups. Twenty age-matched normal subjects served as the control group. Septal, lateral, anterior, inferior, anteroseptal and posterior walls of the left ventricle were respectively scanned using color tissue Doppler imaging (TDI). Then SR and strain curves were derived from TDI for basal, middle and apical segments of each wall. SRI parameters were: Systolic SR (SRsys), systolic strain (εsys) and maximum strain (εmax). Results Compared with normal segments, SRsys, εsys and εmax decreased significantly in the infarct and ischemic segments (P<0.01). Compared with ischemic segments, SRsys, εsys and εmax decreased significantly in the infarct segments (P<0.05). Conclusions SRsys, εsys and εmax measured by SRI can be used to quantitatively analyze regional left ventricular systolic dysfunction in patients with coronary artery disease, and aid in differentiating infarct from ischemic myocardium.
文摘A new method of the multiple rates isotemperature is proposed to define the most probable mechanismg(α) of thermal anlaysis; the iterative isoconversional procedure has been employed to estimate apparent activation energyE; the pre-exponential factorA is obtained on the basis ofE andg(α). By this new method, the thermal analysis kinetics triplet of dehydration of cobalt oxalate dihydrate is determined, apparent activation energyE is 99.84 kJ·mol?1; pre-exponential factorA is 3.427×109–3.872×109 s?1 and the most probable mechanism belongs to nucleation and growth,A m model, the range ofm is from 1.50 to 1.70. Key words multiple rates isotemperature method - isoconversional method - cobalt oxalate dihydrate - accomodation function - differential scanning calorimetry (DSC) CLC number O 636.1 Foundation item: Supported by the Key Foundation of the Science and Technology Committee of Hubei Province (2001ABA009)Biography: Li Li-qing (1977-), female, Master candidate, research direction: material synthesize and thermal analysis kinetics.
文摘目的分析腹膜透析(peritoneal dialysis,PD)患者残余肾功能(residual renal function,RRF)快速下降的危险因素并构建预测模型。方法纳入2012年1月1日—2022年12月31日于中南大学湘雅二医院肾内科就诊的PD患者,以RRF下降速率的中位数将患者分为快速下降组和缓慢下降组。应用最小绝对收缩与选择算子(least absolute shrinkage and selection operator,LASSO)回归初步筛选变量,再通过多因素逐步Logistic回归分析确定RRF快速下降的独立危险因素,并构建列线图预测模型。受试者工作特征(receiver operator characteristic,ROC)曲线下面积(area under the curve,AUC)、校准曲线、Hosmer-Lemeshow检验和决策曲线分析(decision curve analysis,DCA)评估模型的效能,并使用Bootstrap法进行内部验证。结果共纳入710例患者,其中快速下降组354例,缓慢下降组356例。LASSO回归及多因素逐步Logistic回归分析提示体质量指数(body mass index,BMI)>28 kg/m2(OR=2.640,95%CI:1.180~5.926,P=0.018)、基线RRF≥2(OR=3.140,95%CI:1.845~5.342,P<0.001)及血镁(OR=0.341,95%CI:0.128~0.909,P=0.032)是PD患者RRF快速下降的独立危险因素。基于以上因素构建的列线图预测模型AUC为0.719(95%CI:0.682~0.756)。经1000次Bootstrap法重采样内部验证后的AUC为0.722(95%CI:0.685~0.759),Hosmer-Lemeshow拟合优度检验结果为χ^(2)=5.268(P=0.729),DAC显示其临床适用性阈概率范围为0.01~0.91。结论BMI、基线RRF、血镁是PD患者RRF快速下降的独立危险因素,基于此构建的列线图预测模型具有良好的区分度、校准度和临床适用度。
