In three-dimensional imaging employing phase-shifting profilometry(PSP), the nonlinear response of projector and camera makes the fringe gray distribution non-sinusoidal, which further leads to phase error. Although t...In three-dimensional imaging employing phase-shifting profilometry(PSP), the nonlinear response of projector and camera makes the fringe gray distribution non-sinusoidal, which further leads to phase error. Although the double 3-step phaseshifting method is simple and effective, it needs to add an additional set of fringe sequences, which reduces the measurement efficiency. To this end, this paper introduces a generic and flexible self-correction method for nonlinearity-induced phase error.First, according to the nonlinearity-induced phase error model, we introduce an additional wrapped phase with a phase difference of π/3. The error waveform of the two wrapped phases is opposite but not coincident. Then, we introduce an estimation algorithm for the additional wrapped phase offset. Finally, we fuse the two wrapped phases to correct the phase error. Experiments confirm that the root mean squared error of the proposed method is 64.1% lower than that of the traditional method and 13.3% lower than that of the Hilbert transform method. The proposed method does not require any additional fringes or hardware assistance and can be easily extended to 4-step or 5-step PSP.展开更多
To correct a lower limb deformity, orthopedic surgeons must have an exact understanding of the deformity. In general, preoperative planning is carried out using anterior-posterior (AP) and lateral radiographs. However...To correct a lower limb deformity, orthopedic surgeons must have an exact understanding of the deformity. In general, preoperative planning is carried out using anterior-posterior (AP) and lateral radiographs. However, for severe cases with a combination of angular and rotational deformities of the lower limb, obtaining true AP and lateral radiographs is difficult and accurate calculation of the rotational deformity from radiographs is impossible. In this report, we propose to focus on preoperative assessment using three-dimensional (3D) reconstruction images of computed tomography (CT) scans for severe lower limb deformity in a patient with bilateral fibular hemimelia type II according to the Achterman- Kalamchi classification. She underwent bifocal deformity corrections of the bilateral tibiae using Taylor spatial frames in combination with the Ilizarov external fixator. Complete bony union was achieved, without angular deformity or limb length discrepancy.展开更多
Coastal seas,located between continents and the open ocean,are an important active carbon pool.The sedimentary total organic carbon(TOC)in these areas is a mixture of terrestrial and marine sources,and can be a powerf...Coastal seas,located between continents and the open ocean,are an important active carbon pool.The sedimentary total organic carbon(TOC)in these areas is a mixture of terrestrial and marine sources,and can be a powerful proxy for tracing natural processes and human activities.In this study,one fine-grained sediment core(DH5-1) from the inner shelf of the East China Sea was systematically analyzed for TOC and black carbon(BC) contents and TOC stable carbon isotope ratios(d13 C).By combining these data with 210~Pb dating,an improved carbon correction model and a two end-member mixing model,we reconstructed century-scale high-resolution sequences of corrected TOC,terrestrial TOC and marine TOC contents and identified two carbon depletion events in the DH5-1 record.The two events,shown as two minima in the TOC profiles,correspond temporally to 1985-1987 AD and 2003-2006 AD,which exactly matches the water impoundment of the Gezhouba Dam and Three Gorges Dam,respectively.In addition,the variations in TOC contents and δ^(13)C values before,during or after the minima demonstrate a relationship between the depletion events and water impoundment of the dams on the Changjiang River.The TOC reductions may represent synchronous responses of sedimentary TOC and resultant ecological ef fects on the inner shelf of the East China Sea to the water impoundment of the dams.These new TOC records reflect the interaction between natural and anthropogenic processes and,accordingly,provide a deep insight and important references for assessing marine ecological ef fects resulting from water impoundment of largescale dams.展开更多
AIM: To assess the sutureless scleral fixation technique for posterior chamber foldable intraocular lens(PCIOL) implantation in aphakic eyes with insufficient or no capsular support. METHODS: A technique for sutureles...AIM: To assess the sutureless scleral fixation technique for posterior chamber foldable intraocular lens(PCIOL) implantation in aphakic eyes with insufficient or no capsular support. METHODS: A technique for sutureless intrascleral fixation of the haptics of a standard 3-piece PCIOL was used which ensures sutureless fixation by permanent incarceration of the haptics in a scleral tunnel parallel to the limbus. All patients were evaluated for preoperative status [visual acuity, refractive error, K readings, intraocular pressure(IOP) measurement, slit lamp examination, fundus examination and optical biometry], postoperative status and complications. Ultrasound biomicroscopy(UBM) was done for 10 cases to evaluate optic tilt. RESULTS: The study evaluated 42 eyes of 42 patients. The follow-up period was 6 mo. Improvement of best corrected visual acuity(BCVA) one line occurred in 10 cases(23.8%) and loss of one line in 3 cases(7.1%). Intraoperative complications included: haptic kink in 4 cases(9.5%), haptic breakage in 1 case(2.4%), haptic dislocation in 1 case(2.4%), haptic slippage in 3 cases(7.1%), IOL dislocation in 1 case(2.4%) and sclerotomy related bleeding in 1 case(2.4%). Postoperative complications included: transient mild vitreous hemorrhage in 3 cases(7.1%), choroidal detachment in 1 case(2.4%), cystoid macular edema(CME) in 1 case(2.4%), optic capture in 1 case(2.4%), subconjunctival haptic in 2 cases(4.8%), ocular hypotony in 4 cases(9.5%) and ocular hypertension in 1 case(2.4%). There were no cases of retinal detachment or endophthalmitis. UBM showed optic tilt in 3 cases(30%). CONCLUSION: Fixation of three-piece foldable IOL haptics in scleral tunnel parallel to the limbus-providedaxial stability and proper centration of the IOL with minimal or no tilt in most cases and a low complication rate during the follow up period which lasted 6 mo.展开更多
Magnetometric resistivity(MMR)method is a new way to detect dam leakage.The coil sensor is generally used to collect data in geophysical exploration methods.Given the characteristics of accurate vector data requiremen...Magnetometric resistivity(MMR)method is a new way to detect dam leakage.The coil sensor is generally used to collect data in geophysical exploration methods.Given the characteristics of accurate vector data requirements and high sensitivity requirement,a three-component MMR air-core coil sensor is designed.Through the analysis of sensor sensitivity and coil structure parameters,the coil structure and turn number are designed.By analyzing the noise source of the sensor,a suitable amplifier is selected to reduce the background noise of the system.Through the analysis of the three-component non-orthogonal angles,the parameters of the non-orthogonal angles of the coils are corrected.Finally,a three-component MMR induction magnetic field sensor is designed.The volume of the sensor is controlled at 0.027 m 3.The background noise of X、Y and Z are 5.030435 nV/Hz@380 Hz and magnetic field sensitivities are 0.18995 pT/Hz@380 Hz.The three channels have good consistency,and the three-component nonorthogonal angles correction error of three components is controlled within 0.2%.展开更多
In predictive direct power control(PDPC)system of three-phase pulse width modulation(PWM)rectifier,grid voltage sensor makes the whole system more complex and costly.Therefore,third-order generalized integrator(TOGI)i...In predictive direct power control(PDPC)system of three-phase pulse width modulation(PWM)rectifier,grid voltage sensor makes the whole system more complex and costly.Therefore,third-order generalized integrator(TOGI)is used to generate orthogonal signals with the same frequency to estimate the grid voltage.In addition,in view of the deviation between actual and reference power in the three-phase PWM rectifier traditional PDPC strategy,a power correction link is designed to correct the power reference value.The grid voltage sensor free algorithm based on TOGI and the corrected PDPC strategy are applied to three-phase PWM rectifier and simulated on the simulation platform.Simulation results show that the proposed method can effectively eliminate the power tracking deviation and the grid voltage.The effectiveness of the proposed method is verified by comparing the simulation results.展开更多
To evaluate the results of the TRAFIX instrumentation in correcting s coliosis. Methods. Since October 1997, 47 patients with scoliosis received spinal fixation with the TRAFIX instrumentation at the Peking Union Medi...To evaluate the results of the TRAFIX instrumentation in correcting s coliosis. Methods. Since October 1997, 47 patients with scoliosis received spinal fixation with the TRAFIX instrumentation at the Peking Union Medical College Hospital. T he average age was 14.3 years (range 10 to 38 years). There were 27 idiopathic c ases, 16 congenital cases, 2 cases with Marfan syndrome and 2 with neurofibromat osis. Twelve of the 47 patients underwent anterior release, while 4 patients rec eived the revision approach. The average follow up time was 26 months (13～38 m onths). Results. The measurements of primary coronal deformity before and after surgery were 74°(50°～115°) and 38.7° (11°～95°), respectively. The average curve correction was 54%. The average number of fused segments was 12.5 (7～17) verte brae. The distance between the center of apex and the C7 plumb line was 56.8 mm before surgery (25～107mm) and 31 mm after surgery (10～87mm). Conclusion. The TRAFIX instrumentation provides three dimensional correction wi th refinement, convenience and reliable fixation.展开更多
基金supported by the Natural Science Foundation of Shandong Province (No. ZR2021MF024)the National Natural Science Foundation of China (No. 62273274)。
文摘In three-dimensional imaging employing phase-shifting profilometry(PSP), the nonlinear response of projector and camera makes the fringe gray distribution non-sinusoidal, which further leads to phase error. Although the double 3-step phaseshifting method is simple and effective, it needs to add an additional set of fringe sequences, which reduces the measurement efficiency. To this end, this paper introduces a generic and flexible self-correction method for nonlinearity-induced phase error.First, according to the nonlinearity-induced phase error model, we introduce an additional wrapped phase with a phase difference of π/3. The error waveform of the two wrapped phases is opposite but not coincident. Then, we introduce an estimation algorithm for the additional wrapped phase offset. Finally, we fuse the two wrapped phases to correct the phase error. Experiments confirm that the root mean squared error of the proposed method is 64.1% lower than that of the traditional method and 13.3% lower than that of the Hilbert transform method. The proposed method does not require any additional fringes or hardware assistance and can be easily extended to 4-step or 5-step PSP.
文摘To correct a lower limb deformity, orthopedic surgeons must have an exact understanding of the deformity. In general, preoperative planning is carried out using anterior-posterior (AP) and lateral radiographs. However, for severe cases with a combination of angular and rotational deformities of the lower limb, obtaining true AP and lateral radiographs is difficult and accurate calculation of the rotational deformity from radiographs is impossible. In this report, we propose to focus on preoperative assessment using three-dimensional (3D) reconstruction images of computed tomography (CT) scans for severe lower limb deformity in a patient with bilateral fibular hemimelia type II according to the Achterman- Kalamchi classification. She underwent bifocal deformity corrections of the bilateral tibiae using Taylor spatial frames in combination with the Ilizarov external fixator. Complete bony union was achieved, without angular deformity or limb length discrepancy.
基金Supported by the National Basic Research Program of China(973 Program)(No.2012CB956004)the Fundamental Research Funds for the Central Universities(No.16lgjc22)
文摘Coastal seas,located between continents and the open ocean,are an important active carbon pool.The sedimentary total organic carbon(TOC)in these areas is a mixture of terrestrial and marine sources,and can be a powerful proxy for tracing natural processes and human activities.In this study,one fine-grained sediment core(DH5-1) from the inner shelf of the East China Sea was systematically analyzed for TOC and black carbon(BC) contents and TOC stable carbon isotope ratios(d13 C).By combining these data with 210~Pb dating,an improved carbon correction model and a two end-member mixing model,we reconstructed century-scale high-resolution sequences of corrected TOC,terrestrial TOC and marine TOC contents and identified two carbon depletion events in the DH5-1 record.The two events,shown as two minima in the TOC profiles,correspond temporally to 1985-1987 AD and 2003-2006 AD,which exactly matches the water impoundment of the Gezhouba Dam and Three Gorges Dam,respectively.In addition,the variations in TOC contents and δ^(13)C values before,during or after the minima demonstrate a relationship between the depletion events and water impoundment of the dams on the Changjiang River.The TOC reductions may represent synchronous responses of sedimentary TOC and resultant ecological ef fects on the inner shelf of the East China Sea to the water impoundment of the dams.These new TOC records reflect the interaction between natural and anthropogenic processes and,accordingly,provide a deep insight and important references for assessing marine ecological ef fects resulting from water impoundment of largescale dams.
文摘AIM: To assess the sutureless scleral fixation technique for posterior chamber foldable intraocular lens(PCIOL) implantation in aphakic eyes with insufficient or no capsular support. METHODS: A technique for sutureless intrascleral fixation of the haptics of a standard 3-piece PCIOL was used which ensures sutureless fixation by permanent incarceration of the haptics in a scleral tunnel parallel to the limbus. All patients were evaluated for preoperative status [visual acuity, refractive error, K readings, intraocular pressure(IOP) measurement, slit lamp examination, fundus examination and optical biometry], postoperative status and complications. Ultrasound biomicroscopy(UBM) was done for 10 cases to evaluate optic tilt. RESULTS: The study evaluated 42 eyes of 42 patients. The follow-up period was 6 mo. Improvement of best corrected visual acuity(BCVA) one line occurred in 10 cases(23.8%) and loss of one line in 3 cases(7.1%). Intraoperative complications included: haptic kink in 4 cases(9.5%), haptic breakage in 1 case(2.4%), haptic dislocation in 1 case(2.4%), haptic slippage in 3 cases(7.1%), IOL dislocation in 1 case(2.4%) and sclerotomy related bleeding in 1 case(2.4%). Postoperative complications included: transient mild vitreous hemorrhage in 3 cases(7.1%), choroidal detachment in 1 case(2.4%), cystoid macular edema(CME) in 1 case(2.4%), optic capture in 1 case(2.4%), subconjunctival haptic in 2 cases(4.8%), ocular hypotony in 4 cases(9.5%) and ocular hypertension in 1 case(2.4%). There were no cases of retinal detachment or endophthalmitis. UBM showed optic tilt in 3 cases(30%). CONCLUSION: Fixation of three-piece foldable IOL haptics in scleral tunnel parallel to the limbus-providedaxial stability and proper centration of the IOL with minimal or no tilt in most cases and a low complication rate during the follow up period which lasted 6 mo.
文摘Magnetometric resistivity(MMR)method is a new way to detect dam leakage.The coil sensor is generally used to collect data in geophysical exploration methods.Given the characteristics of accurate vector data requirements and high sensitivity requirement,a three-component MMR air-core coil sensor is designed.Through the analysis of sensor sensitivity and coil structure parameters,the coil structure and turn number are designed.By analyzing the noise source of the sensor,a suitable amplifier is selected to reduce the background noise of the system.Through the analysis of the three-component non-orthogonal angles,the parameters of the non-orthogonal angles of the coils are corrected.Finally,a three-component MMR induction magnetic field sensor is designed.The volume of the sensor is controlled at 0.027 m 3.The background noise of X、Y and Z are 5.030435 nV/Hz@380 Hz and magnetic field sensitivities are 0.18995 pT/Hz@380 Hz.The three channels have good consistency,and the three-component nonorthogonal angles correction error of three components is controlled within 0.2%.
基金National Natural Science Foundation of China(Nos.51767013,52067013)。
文摘In predictive direct power control(PDPC)system of three-phase pulse width modulation(PWM)rectifier,grid voltage sensor makes the whole system more complex and costly.Therefore,third-order generalized integrator(TOGI)is used to generate orthogonal signals with the same frequency to estimate the grid voltage.In addition,in view of the deviation between actual and reference power in the three-phase PWM rectifier traditional PDPC strategy,a power correction link is designed to correct the power reference value.The grid voltage sensor free algorithm based on TOGI and the corrected PDPC strategy are applied to three-phase PWM rectifier and simulated on the simulation platform.Simulation results show that the proposed method can effectively eliminate the power tracking deviation and the grid voltage.The effectiveness of the proposed method is verified by comparing the simulation results.
文摘To evaluate the results of the TRAFIX instrumentation in correcting s coliosis. Methods. Since October 1997, 47 patients with scoliosis received spinal fixation with the TRAFIX instrumentation at the Peking Union Medical College Hospital. T he average age was 14.3 years (range 10 to 38 years). There were 27 idiopathic c ases, 16 congenital cases, 2 cases with Marfan syndrome and 2 with neurofibromat osis. Twelve of the 47 patients underwent anterior release, while 4 patients rec eived the revision approach. The average follow up time was 26 months (13～38 m onths). Results. The measurements of primary coronal deformity before and after surgery were 74°(50°～115°) and 38.7° (11°～95°), respectively. The average curve correction was 54%. The average number of fused segments was 12.5 (7～17) verte brae. The distance between the center of apex and the C7 plumb line was 56.8 mm before surgery (25～107mm) and 31 mm after surgery (10～87mm). Conclusion. The TRAFIX instrumentation provides three dimensional correction wi th refinement, convenience and reliable fixation.
