Based on the scattering characteristic,the comparison of RCS(radar cross-section)at different positions of a target in the same direction of incidence can be obtained first by extruding or deleting part of the entity....Based on the scattering characteristic,the comparison of RCS(radar cross-section)at different positions of a target in the same direction of incidence can be obtained first by extruding or deleting part of the entity.A simulation method of aerial&space targets echo characteristics(A&STEC)is proposed that is universal to aerial and space targets.We utilize a fixed-wing UAV(unmanned aerial vehicle)and typical missiles in simulation.The echo signal modulation characteristic parameters are calculated theoretically by the atmospheric attenuation model,the finite element method and a MUMPS solver.The verification simulations show that this method can analyze the influence of the target shape,incident direction,detection position and detection frequency on echo waveform,intensity and energy distribution.The results show that the profile of echo waveform can invert the general shape of the target.The relationship between time and intensity can determine whether the target is moving towards or away from the detector in addition.These conclusions can provide a reference for the ballistic missile target tracking and the defense against UVA intrusion in theory.展开更多
BACKGROUND The main clinical treatment for esophageal cancer is surgery. Since traditional open esophageal cancer resection has the disadvantages of large trauma, long recovery period, and high postoperative complicat...BACKGROUND The main clinical treatment for esophageal cancer is surgery. Since traditional open esophageal cancer resection has the disadvantages of large trauma, long recovery period, and high postoperative complication rate, its clinical application is gradually reduced. The current report of minimally invasive Ivor-Lewis esophagectomy(MIILE) is increasing. However, researchers found that patients with MIILE had a higher incidence of early delayed gastric emptying(DGE).AIM To investigate the influencing factors of postoperative early DGE after MIILE.METHODS A total of 156 patients diagnosed with esophageal cancer at Deyang People's Hospital were enrolled. According to the criteria of DGE, patients were assigned to a DGE group(n = 49) and a control group(n = 107). The differences between the DGE group and the control group were compared. Multivariate logistic regression analysis was used to further determine the influencing factors of postoperative early DGE. The receiver operating characteristic(ROC) curve was used to assess potential factors in predicting postoperative early DGE.RESULTS Age, intraoperative blood loss, chest drainage time, portion of anxiety score ≥ 45 points, analgesia pump use, postoperative to enteral nutrition interval, and postoperative fluid volume in the DGE group were higher than those in the control group. Perioperative albumin level in the DGE group was lower than that in the control group(P < 0.05). Age, anxiety score, perioperative albumin level,and postoperative fluid volume were independent factors influencing postoperative early DGE, and the differences were statistically significant(P <0.05). The ROC curve analysis revealed that the area under the curve(AUC) foranxiety score was 0.720. The optimum cut-off value was 39, and the sensitivity and specificity were 80.37% and 65.31%, respectively. The AUC for postoperative fluid volume were 0.774. The optimal cut-off value was 1191.86 mL, and the sensitivity and specificity were 65.3% and 77.6%, respectively. The AUC for perioperative albumin level was 0.758. The optimum cut-off value was 26.75 g/L,and the sensitivity and specificity were 97.2% and 46.9%, respectively.CONCLUSION Advanced age, postoperative anxiety, perioperative albumin level, and postoperative fluid volume can increase the incidence of postoperative early DGE.展开更多
BACKGROUND The pedicle screw technique is widely employed for vertebral body fixation in the treatment of spinal disorders.However,traditional screw placement methods require the dissection of paraspinal muscles and t...BACKGROUND The pedicle screw technique is widely employed for vertebral body fixation in the treatment of spinal disorders.However,traditional screw placement methods require the dissection of paraspinal muscles and the insertion of pedicle screws at specific transverse section angles(TSA).Larger TSA angles require more force to pull the muscle tissue,which can increase the risk of surgical trauma and ischemic injury to the lumbar muscles.AIM To study the feasibility of zero-degree TSA vertical pedicle screw technique in the lumbosacral segment.METHODS Finite element models of vertebral bodies and pedicle screw-rod systems were established for the L4-S1 spinal segments.A standard axial load of 500 N and a rotational torque of 10 N/m were applied.Simulated screw pull-out experiment was conducted to observe pedicle screw resistance to pull-out,maximum stress,load-displacement ratio,maximum stress in vertebral bodies,load-displacement ratio in vertebral bodies,and the stress distribution in pedicle screws and vertebral bodies.Differences between the 0-degree and 17-degree TSA were compared.RESULTS At 0-degree TSA,the screw pull-out force decreased by 11.35%compared to that at 17-degree TSA(P<0.05).At 0-degree and 17-degree TSA,the stress range in the screw-rod system was 335.1-657.5 MPa and 242.8-648.5 MPa,separately,which were below the fracture threshold for the screw-rod system(924 MPa).At 0-degree and 17-degree TSA,the stress range in the vertebral bodies was 68.45-78.91 MPa and 39.08-72.73 MPa,separately,which were below the typical bone yield stress range for vertebral bodies(110-125 MPa).At 0-degree TSA,the load-displacement ratio for the vertebral bodies and pedicle screws was slightly lower compared to that at 17-degree TSA,indicating slightly lower stability(P<0.05).CONCLUSION The safety and stability of 0-degree TSA are slightly lower,but the risks of screw-rod system fracture,vertebral body fracture,and rupture are within acceptable limits.展开更多
One hundred and sixty plots, approximately every 100 m above sea level （a.s.1.） along an altitudinal gradient from 470 to 3 080 m a.s.1, at the southern and northern watershed of Mt. Shennongjia, China, were examine...One hundred and sixty plots, approximately every 100 m above sea level （a.s.1.） along an altitudinal gradient from 470 to 3 080 m a.s.1, at the southern and northern watershed of Mt. Shennongjia, China, were examined to determine the altitudinal pattern of plant species diversity. Mt. Shennongjia was found to have high plant species diversity, with 3 479 higher plants recorded. Partial correlation analysis and detrended canonical correspondence analysis （DCCA） based on plant species diversity revealed that altitude was the main factor affecting the spatial pattern of plant species diversity on Mt. Shennongjia and that canopy coverage of the arbor layer also had a considerable effect on plant species diversity. The DCCA based on species data of importance value further revealed that altitude gradient was the primary factor shaping the spatial pattern of plant species. In addition, the rule of the “mid-altitude bulge” was supported on Mt. Shennongjia. Plant species diversity was closely related to vegetation type and the transition zone usually had a higher diversity. Higher plant species diversity appeared in the mixed evergreen and deciduous broadleaved forest zone （900-1500 m a.s.1.） and its transition down to evergreen broadleaved forest zone or up to deciduous broadleaved forest zone. The largest plant species diversity in whole communities on Mt. Shennongjia lay at approximately 1 200 m a.s.1. Greatest tree diversity, shrub diversity, and grass diversity was found at approximately 1 500, 1 100, and 1 200 m a.s.l., respectively. The southern watershed showed higher plant species diversity than the northern watershed, with maximum plant species diversity at a higher altitude in the southern watershed than the northern watershed. These results indicate that Mt. Shennongjia shows characteristics of a transition region. The relationship between the altitudinal pattern of plant species diversity and the vegetation type in eastern China are also discussed and a hypothesis about the altitudinal pattern of plant species diversity in eastern China is proposed.展开更多
文摘Based on the scattering characteristic,the comparison of RCS(radar cross-section)at different positions of a target in the same direction of incidence can be obtained first by extruding or deleting part of the entity.A simulation method of aerial&space targets echo characteristics(A&STEC)is proposed that is universal to aerial and space targets.We utilize a fixed-wing UAV(unmanned aerial vehicle)and typical missiles in simulation.The echo signal modulation characteristic parameters are calculated theoretically by the atmospheric attenuation model,the finite element method and a MUMPS solver.The verification simulations show that this method can analyze the influence of the target shape,incident direction,detection position and detection frequency on echo waveform,intensity and energy distribution.The results show that the profile of echo waveform can invert the general shape of the target.The relationship between time and intensity can determine whether the target is moving towards or away from the detector in addition.These conclusions can provide a reference for the ballistic missile target tracking and the defense against UVA intrusion in theory.
基金Supported by Science and Technology Support Plan of Sichuan Deyang Technology Bureau,No.2015SZ023
文摘BACKGROUND The main clinical treatment for esophageal cancer is surgery. Since traditional open esophageal cancer resection has the disadvantages of large trauma, long recovery period, and high postoperative complication rate, its clinical application is gradually reduced. The current report of minimally invasive Ivor-Lewis esophagectomy(MIILE) is increasing. However, researchers found that patients with MIILE had a higher incidence of early delayed gastric emptying(DGE).AIM To investigate the influencing factors of postoperative early DGE after MIILE.METHODS A total of 156 patients diagnosed with esophageal cancer at Deyang People's Hospital were enrolled. According to the criteria of DGE, patients were assigned to a DGE group(n = 49) and a control group(n = 107). The differences between the DGE group and the control group were compared. Multivariate logistic regression analysis was used to further determine the influencing factors of postoperative early DGE. The receiver operating characteristic(ROC) curve was used to assess potential factors in predicting postoperative early DGE.RESULTS Age, intraoperative blood loss, chest drainage time, portion of anxiety score ≥ 45 points, analgesia pump use, postoperative to enteral nutrition interval, and postoperative fluid volume in the DGE group were higher than those in the control group. Perioperative albumin level in the DGE group was lower than that in the control group(P < 0.05). Age, anxiety score, perioperative albumin level,and postoperative fluid volume were independent factors influencing postoperative early DGE, and the differences were statistically significant(P <0.05). The ROC curve analysis revealed that the area under the curve(AUC) foranxiety score was 0.720. The optimum cut-off value was 39, and the sensitivity and specificity were 80.37% and 65.31%, respectively. The AUC for postoperative fluid volume were 0.774. The optimal cut-off value was 1191.86 mL, and the sensitivity and specificity were 65.3% and 77.6%, respectively. The AUC for perioperative albumin level was 0.758. The optimum cut-off value was 26.75 g/L,and the sensitivity and specificity were 97.2% and 46.9%, respectively.CONCLUSION Advanced age, postoperative anxiety, perioperative albumin level, and postoperative fluid volume can increase the incidence of postoperative early DGE.
基金the institutional review board of Mingzhou Hospital of Ningbo(No.202208501).
文摘BACKGROUND The pedicle screw technique is widely employed for vertebral body fixation in the treatment of spinal disorders.However,traditional screw placement methods require the dissection of paraspinal muscles and the insertion of pedicle screws at specific transverse section angles(TSA).Larger TSA angles require more force to pull the muscle tissue,which can increase the risk of surgical trauma and ischemic injury to the lumbar muscles.AIM To study the feasibility of zero-degree TSA vertical pedicle screw technique in the lumbosacral segment.METHODS Finite element models of vertebral bodies and pedicle screw-rod systems were established for the L4-S1 spinal segments.A standard axial load of 500 N and a rotational torque of 10 N/m were applied.Simulated screw pull-out experiment was conducted to observe pedicle screw resistance to pull-out,maximum stress,load-displacement ratio,maximum stress in vertebral bodies,load-displacement ratio in vertebral bodies,and the stress distribution in pedicle screws and vertebral bodies.Differences between the 0-degree and 17-degree TSA were compared.RESULTS At 0-degree TSA,the screw pull-out force decreased by 11.35%compared to that at 17-degree TSA(P<0.05).At 0-degree and 17-degree TSA,the stress range in the screw-rod system was 335.1-657.5 MPa and 242.8-648.5 MPa,separately,which were below the fracture threshold for the screw-rod system(924 MPa).At 0-degree and 17-degree TSA,the stress range in the vertebral bodies was 68.45-78.91 MPa and 39.08-72.73 MPa,separately,which were below the typical bone yield stress range for vertebral bodies(110-125 MPa).At 0-degree TSA,the load-displacement ratio for the vertebral bodies and pedicle screws was slightly lower compared to that at 17-degree TSA,indicating slightly lower stability(P<0.05).CONCLUSION The safety and stability of 0-degree TSA are slightly lower,but the risks of screw-rod system fracture,vertebral body fracture,and rupture are within acceptable limits.
文摘One hundred and sixty plots, approximately every 100 m above sea level （a.s.1.） along an altitudinal gradient from 470 to 3 080 m a.s.1, at the southern and northern watershed of Mt. Shennongjia, China, were examined to determine the altitudinal pattern of plant species diversity. Mt. Shennongjia was found to have high plant species diversity, with 3 479 higher plants recorded. Partial correlation analysis and detrended canonical correspondence analysis （DCCA） based on plant species diversity revealed that altitude was the main factor affecting the spatial pattern of plant species diversity on Mt. Shennongjia and that canopy coverage of the arbor layer also had a considerable effect on plant species diversity. The DCCA based on species data of importance value further revealed that altitude gradient was the primary factor shaping the spatial pattern of plant species. In addition, the rule of the “mid-altitude bulge” was supported on Mt. Shennongjia. Plant species diversity was closely related to vegetation type and the transition zone usually had a higher diversity. Higher plant species diversity appeared in the mixed evergreen and deciduous broadleaved forest zone （900-1500 m a.s.1.） and its transition down to evergreen broadleaved forest zone or up to deciduous broadleaved forest zone. The largest plant species diversity in whole communities on Mt. Shennongjia lay at approximately 1 200 m a.s.1. Greatest tree diversity, shrub diversity, and grass diversity was found at approximately 1 500, 1 100, and 1 200 m a.s.l., respectively. The southern watershed showed higher plant species diversity than the northern watershed, with maximum plant species diversity at a higher altitude in the southern watershed than the northern watershed. These results indicate that Mt. Shennongjia shows characteristics of a transition region. The relationship between the altitudinal pattern of plant species diversity and the vegetation type in eastern China are also discussed and a hypothesis about the altitudinal pattern of plant species diversity in eastern China is proposed.
