The dynamical equations of a thin rectangle plate subjected to the friction support boundary and its plane force are established in this paper. The local bifurcation of this system is investigated by using L S method...The dynamical equations of a thin rectangle plate subjected to the friction support boundary and its plane force are established in this paper. The local bifurcation of this system is investigated by using L S method and the singularity theory. The Z 2 bifurcation in non degenerate case is discussed. The local bifurcation diagrams of the unfolding parameters and the bifurcation response characters referred to the physical parameters of the system are obtained by numerical simulation. The results of the computer simulation are coincident with the theoretical analysis and experimental results.展开更多
The effect of rectangle wave pulse current on solidification structure of ZA27 alloy was studied. The restdts show that the wave pattern relies on the frequency range of harmonic wave and the energy of pulse current w...The effect of rectangle wave pulse current on solidification structure of ZA27 alloy was studied. The restdts show that the wave pattern relies on the frequency range of harmonic wave and the energy of pulse current within the frequency range of pulse current. Imposed pulse current could induce the solidification system to oscillate. The frequency range and the relevant energy distribution of pulse current exert an influence on the amount of atoms involved for forming critical nucleus, the surface states of dusters in melt, the oscillating state of melt on the surface of dusters, the active energy of atom diffusion , the frequnce response of the resonance of bulk melt and the absorbability of the solidification system to the external work. Rectangle wave pulse current involves rich harmonic waves ; the amplitudes of high order of harmonic waves are higher and reduce slowly, so it has a better effect on inoculation and modification.展开更多
As a coprocessor, field-programmable gate array （FPGA） is the hardware computing processor accelerating the computing capacity of coraputers. To efficiently manage the hardware free resources for the placing of task...As a coprocessor, field-programmable gate array （FPGA） is the hardware computing processor accelerating the computing capacity of coraputers. To efficiently manage the hardware free resources for the placing of tasks on FPGA and take full advantage of the partially reconfigurable units, good utilization of chip resources is an important and necessary work. In this paper, a new method is proposed to find the complete set of maximal free resource rectangles based on the cross point of edge lines of running tasks on FPGA area, and the prove process is provided to make sure the correctness of this method.展开更多
In this paper, the principle of multi-point forming (MPF) technique is presented. One of the most serious defects, wrinkling, during the multi-point forming process of a shallow rectangle cup is discussed by means of ...In this paper, the principle of multi-point forming (MPF) technique is presented. One of the most serious defects, wrinkling, during the multi-point forming process of a shallow rectangle cup is discussed by means of numerical simulation on the shallow rectangle cup forming process. The effects of thickness, material of sheet metal and the pressure of the blank holder are investigated. Based on the simulation results, the reasons and control methods of wrinkling are pointed out. Moreover, the experiment on the multi-point die forming of the shallow rectangle cup by the MPF machine is done to validate the efficiency of the numerical simulation, and the result proves that the application of an elastic cushion in the forming can restrain wrinkling efficiently.展开更多
The problem of tiling rectangles by polyominoes generated large interest. A related one is the problem of tiling parallelograms by twisted polyominoes. Both problems are related with tilings of (skewed) quadrants by p...The problem of tiling rectangles by polyominoes generated large interest. A related one is the problem of tiling parallelograms by twisted polyominoes. Both problems are related with tilings of (skewed) quadrants by polyominoes. Indeed, if all tilings of a (skewed) quadrant by a tile set can be reduced to a tiling by congruent rectangles (parallelograms), this provides information about tilings of rectangles (parallelograms). We consider a class of tile sets in a square lattice appearing from arbitrary dissections of rectangles in two L-shaped polyominoes and from symmetries of these tiles about the first bisector. Only translations of the tiles are allowed in a tiling. If the sides of the dissected rectangle are coprime, we show the existence of tilings of all (skewed) quadrants that do not follow the rectangular (parallelogram) pattern. If one of the sides of the dissected rectangle is 2 and the other is odd, we also show tilings of rectangles by the tile set that do not follow the rectangular pattern. If one of the sides of the dissected rectangle is 2 and the other side is even, we show a new infinite family of tile sets that follows the rectangular pattern when tiling one of the quadrants. For this type of dis-section, we also show a new infinite family that does not follow the rectangular pattern when tiling rectangles. Finally, we investigate more general dissections of rectangles, with. Here we show infinite families of tile sets that follow the rectangular pattern for a quadrant and infinite families that do not follow the rectangular pattern for any quadrant. We also show, for infinite families of tile sets of this type, tilings of rectangles that do not follow the rectangular pattern.展开更多
The statistical dynamics of partially incoherent ultrafast lasers are complex and chaotic,which is significant for fundamental research and practical applications.We experimentally and theoretically reveal the statist...The statistical dynamics of partially incoherent ultrafast lasers are complex and chaotic,which is significant for fundamental research and practical applications.We experimentally and theoretically reveal the statistical dynamics of the spectral evolutions and correlations in an incoherent noise-like rectangle pulse laser(NLRPL).Based on statistical histogram analysis,the probability distribution asymmetry of the spectral intensity fluctuation is decayed with the wavelength far away from the spectral peak due to the detection noise.The full-spectral correlation values indicate that the spectral similarity between two round trips is exponentially weakened as the round-trip offset increases.By studying the correlation map of spectral components,we find that the area of the high-correlation region is relevant to the pump power,which is reduced by increasing the pump power.The mutual information of the spectra demonstrates that two spectral components with symmetry about the spectral peak have a statistical dependence.Experimental observations and statistical properties can coincide well with theoretical numerical simulations.We reveal the pump-dependent spectral correlation of the NLRPL and provide multiple statistical methods for the characterizations of chaotic dynamics in incoherent light sources.展开更多
Based on the TRMM dataset, this paper compares the applicability of the improved MCE(minimum circumscribed ellipse), MBR(minimum bounding rectangle), and DIA(direct indexing area) methods for rain cell fitting. These ...Based on the TRMM dataset, this paper compares the applicability of the improved MCE(minimum circumscribed ellipse), MBR(minimum bounding rectangle), and DIA(direct indexing area) methods for rain cell fitting. These three methods can reflect the geometric characteristics of clouds and apply geometric parameters to estimate the real dimensions of rain cells. The MCE method shows a major advantage in identifying the circumference of rain cells. The circumference of rain cells identified by MCE in most samples is smaller than that identified by DIA and MBR, and more similar to the observed rain cells. The area of rain cells identified by MBR is relatively robust. For rain cells composed of many pixels(N> 20), the overall performance is better than that of MCE, but the contribution of MBR to the best identification results,which have the shortest circumference and the smallest area, is less than that of MCE. The DIA method is best suited to small rain cells with a circumference of less than 100 km and an area of less than 120 km^(2), but the overall performance is mediocre. The MCE method tends to achieve the highest success at any angle, whereas there are fewer “best identification”results from DIA or MBR and more of the worst ones in the along-track direction and cross-track direction. Through this comprehensive comparison, we conclude that MCE can obtain the best fitting results with the shortest circumference and the smallest area on behalf of the high filling effect for all sizes of rain cells.展开更多
BACKGROUND For total laparoscopic distal gastrectomies for gastric cancer,the reconstruction method is critical to the clinical outcome of the procedure.However,which reconstruction technique is optimal remains contro...BACKGROUND For total laparoscopic distal gastrectomies for gastric cancer,the reconstruction method is critical to the clinical outcome of the procedure.However,which reconstruction technique is optimal remains controversial.We originally reported the augmented rectangle technique(ART)as a reconstruction option for total laparoscopic Billroth I reconstructions.Still,little is known about its effect on long-term outcomes,specifically the incidence of postgastrectomy syndrome and its impact on quality of life.AIM To analyze postgastrectomy syndrome and quality of life after ART using the Postgastrectomy Syndrome Assessment Scale-37(PGSAS-37)questionnaire.METHODS At Juntendo University,a total of 94 patients who underwent ART for Billroth I reconstruction with total laparoscopic distal gastrectomies for gastric cancer between July 2016 and March 2020 completed the PGSAS-37 questionnaire.Multidimensional analysis was performed,comparing those 94 ART cases from our institution(ART group)to 909 distal gastrectomy cases with a Billroth I reconstruction from other Japanese institutions who also completed the PGSAS-37 as part of a larger national database(PGSAS group).RESULTS Patients in the ART group had significantly better total symptom scores in all the symptom subscales(i.e.,esophageal reflux,abdominal pain,meal-related distress,indigestion,diarrhea,constipation,and dumping).The loss of body weight was marginally greater for those in the ART group than in the PGSAS group(-9.3%vs-7.9%,P=0.054).The ART group scored significantly lower in their dissatisfaction of ongoing symptoms,during meals,and with daily life.CONCLUSION ART for Billroth I reconstruction provided beneficial long-term results for postgastrectomy syndrome and quality of life in patients undergoing total laparoscopic distal gastrectomies for gastric cancer.展开更多
The oil film thickness of oil hydrostatic guide with constant pressure supply based on capillary restrictor is greatly affected by load,and this kind of hydrostatic guide is usually applied to the machine tools with m...The oil film thickness of oil hydrostatic guide with constant pressure supply based on capillary restrictor is greatly affected by load,and this kind of hydrostatic guide is usually applied to the machine tools with moderate load.The static and dynamic characteristics of the guide have been studied by using some theoretical,numerical and experimental approaches,and some methods and measures have been proposed to improve its performances.The hydrostatic guide based on progressive mengen(PM)flow controller is especially suitable for the heavy numerical control(NC)machine tools.However,few literatures about the research on the static and dynamic characteristics of the hydrostatic guides based on PM flow controller are reported.In this paper,the formulae are derived for analyzing the static and dynamic characteristics of hydrostatic guides with rectangle pockets and PM flow controller according to the theory of hydrostatic bearing.On the basis of the analysis of hydrostatic bearing with circular pocket,some equations are derived for solving the static pressure,volume pressure and squeezing pressure which influence the dynamic characteristics of hydrostatic guides with rectangle pocket.The function and the influencing factors of three pressures are clarified.The formulae of amplitude-frequency characteristics and dynamic stiffness of the hydrostatic guide system are derived.With the help of software MATLAB,programs are coded with C++language to simulate numerically the static and dynamic characteristics of the hydrostatic guide based on PM flow controller.The simulation results indicate that the sensitive oil volume between the outlet of the PM flow controller and the guide pocket has the greatest influence on the characteristics of the guide,and it should be reduced as small as possible when the field working condition is met.Choosing the oil with a greater viscosity is also helpful in improving the dynamic performance of hydrostatic guides.The research work has instructing significance for analyzing and designing the guide with PM flow controller.展开更多
The internal quality inspection of the continuous casting billets is very important,and mis-inspection will seriously affect the subsequent production process.The UNet-VGG16 transfer learning model was used for semant...The internal quality inspection of the continuous casting billets is very important,and mis-inspection will seriously affect the subsequent production process.The UNet-VGG16 transfer learning model was used for semantic segmentation of the central shrinkage defects of the continuous casting billets.The automatic recognition accuracy of the central shrinkage defects of the continuous casting billets reaches more than 0.9.We use the minimum circumscribed rectangle to quantify the geometric dimensions such as length,width and area of the central shrinkage defects and use the threshold method to rate the central shrinkage defects of the continuous casting billets.The results show that all the testing images are rated correctly,and this method achieves the automatic recognition and intelligent analysis of the central shrinkage defects of the continuous casting billets.展开更多
Helicopters are widely used in maritime Search and Rescue(SAR) missions. To ensure the success of SAR missions, search areas need to be carefully planned. With the development of computer technology and weather foreca...Helicopters are widely used in maritime Search and Rescue(SAR) missions. To ensure the success of SAR missions, search areas need to be carefully planned. With the development of computer technology and weather forecast technology, the survivors’ drift trajectories can be predicted more precisely, which strongly supports the planning of search areas for the rescue helicopter. However, the methods used to determine the search area based on the predicted drift trajectories are mainly derived from the continuous expansion of the area with the highest Probability of Containment(POC), which may lead to local optimal solutions and a decrease in the Probability of Success(POS), especially when there are several subareas with a high POC. To address this problem, this paper proposes a method based on a Minimum Bounding Rectangle and Kmeans clustering(MBRK). A silhouette coefficient is adopted to analyze the distribution of the survivors’ probable locations, which are divided into multiple clusters with K-means clustering. Then,probability maps are generated based on the minimum bounding rectangle of each cluster. By adding or subtracting one row or column of cells or shifting the planned search area, 12 search methods are used to generate the optimal search area starting from the cell with the highest POC in each probability map. Taking a real case as an example, the simulation experiment results show that the POS values obtained by the MBRK method are higher than those obtained by other methods,which proves that the MBRK method can effectively support the planning of search areas and that K-means clustering improves the POS of search plans.展开更多
In this paper,the classical composite middle rectangle rule for the computation of Cauchy principal value integral(the singular kernel 1=(x-s))is discussed.With the density function approximated only while the singula...In this paper,the classical composite middle rectangle rule for the computation of Cauchy principal value integral(the singular kernel 1=(x-s))is discussed.With the density function approximated only while the singular kernel is calculated analysis,then the error functional of asymptotic expansion is obtained.We construct a series to approach the singular point.An extrapolation algorithm is presented and the convergence rate of extrapolation algorithm is proved.At last,some numerical results are presented to confirm the theoretical results and show the efficiency of the algorithms.展开更多
In many engineering applications, it is necessary to calculate the min-area encasing box of a circumscription. In this paper, an algorithm for generating the min-area rectangle encasing box, based on revolving angle, ...In many engineering applications, it is necessary to calculate the min-area encasing box of a circumscription. In this paper, an algorithm for generating the min-area rectangle encasing box, based on revolving angle, is investigated and hence put forward. The algorithm computes the areas of the outer rectangular bounds of a closed contour in different revolving angles θ by dispersing approach where 0< θ < π/2 because of the axial symmetry. It is very simple, straight forward and highly efficient. The complexity of its computing time reaches O(n·k ). Practical applications suggest its usefulness and efficiency.展开更多
BACKGROUND Total laparoscopic distal gastrectomy(TLDG)is increasing due to some advantages over open surgery,which has generated interest in gastrointestinal surgeons.However,TLDG is technically demanding especially f...BACKGROUND Total laparoscopic distal gastrectomy(TLDG)is increasing due to some advantages over open surgery,which has generated interest in gastrointestinal surgeons.However,TLDG is technically demanding especially for lymphadenectomy and gastrointestinal reconstruction.During the course of training,trainee surgeons have less chances to perform open gastrectomy compared with that of senior surgeons.AIM To evaluate an appropriate,efficient and safe laparoscopic training procedures suitable for trainee surgeons.METHODS Ninety-two consecutive patients with gastric cancer who underwent TLDG plus Billroth I reconstruction using an augmented rectangle technique and involving trainees were reviewed.The trainees were taught a laparoscopic view of surgical anatomy,standard operative procedures and practiced essential laparoscopic skills.The TLDG procedure was divided into regional lymph node dissections and gastrointestinal reconstruction for analyzing trainee skills.Early surgical outcomes were compared between trainees and trainers to clarify the feasibility and safety of TLDG performed by trainees.Learning curves were used to assess the utility of our training system.RESULTS Five trainees performed a total of 52 TLDGs(56.5%),while 40 TLDGs were conducted by two trainers(43.5%).Except for depth of invasion and pathologic stage,there were no differences in clinicopathological characteristics.Trainers performed more D2 gastrectomies than trainees.The total operation time was significantly longer in the trainee group.The time spent during the lesser curvature lymph node dissection and the Billroth I reconstruction were similar between the two groups.No difference was found in postoperative complications between the two groups.The learning curve of the trainees plateaued after five TLDG cases.CONCLUSION Preparing trainees with a laparoscopic view of surgical anatomy,standard operative procedures and practice in essential laparoscopic skills enabled trainees to perform TLDG safely and feasibly.展开更多
The gravity gradient is a secondary derivative of gravity potential,containing more high-frequency information of Earth’s gravity field.Gravity gradient observation data require deducting its prior and intrinsic part...The gravity gradient is a secondary derivative of gravity potential,containing more high-frequency information of Earth’s gravity field.Gravity gradient observation data require deducting its prior and intrinsic parts to obtain more variational information.A model generated from a topographic surface database is more appropriate to represent gradiometric effects derived from near-surface mass,as other kinds of data can hardly reach the spatial resolution requirement.The rectangle prism method,namely an analytic integration of Newtonian potential integrals,is a reliable and commonly used approach to modeling gravity gradient,whereas its computing efficiency is extremely low.A modified rectangle prism method and a graphical processing unit(GPU)parallel algorithm were proposed to speed up the modeling process.The modified method avoided massive redundant computations by deforming formulas according to the symmetries of prisms’integral regions,and the proposed algorithm parallelized this method’s computing process.The parallel algorithm was compared with a conventional serial algorithm using 100 elevation data in two topographic areas(rough and moderate terrain).Modeling differences between the two algorithms were less than 0.1 E,which is attributed to precision differences between single-precision and double-precision float numbers.The parallel algorithm showed computational efficiency approximately 200 times higher than the serial algorithm in experiments,demonstrating its effective speeding up in the modeling process.Further analysis indicates that both the modified method and computational parallelism through GPU contributed to the proposed algorithm’s performances in experiments.展开更多
文摘The dynamical equations of a thin rectangle plate subjected to the friction support boundary and its plane force are established in this paper. The local bifurcation of this system is investigated by using L S method and the singularity theory. The Z 2 bifurcation in non degenerate case is discussed. The local bifurcation diagrams of the unfolding parameters and the bifurcation response characters referred to the physical parameters of the system are obtained by numerical simulation. The results of the computer simulation are coincident with the theoretical analysis and experimental results.
基金Funded by the Natural Science Foundation of Gansu Province(No.ZS021-A25-027-C)
文摘The effect of rectangle wave pulse current on solidification structure of ZA27 alloy was studied. The restdts show that the wave pattern relies on the frequency range of harmonic wave and the energy of pulse current within the frequency range of pulse current. Imposed pulse current could induce the solidification system to oscillate. The frequency range and the relevant energy distribution of pulse current exert an influence on the amount of atoms involved for forming critical nucleus, the surface states of dusters in melt, the oscillating state of melt on the surface of dusters, the active energy of atom diffusion , the frequnce response of the resonance of bulk melt and the absorbability of the solidification system to the external work. Rectangle wave pulse current involves rich harmonic waves ; the amplitudes of high order of harmonic waves are higher and reduce slowly, so it has a better effect on inoculation and modification.
基金Project supported by the Shanghai Leading Academic Discipline Project(Grant No.J50103)the Natural Science Foundation of Jiangxi Province(Grant No.2010GZS0031)the Science Technology Project of Jiangxi Province(Grant No.2010BGB00604)
文摘As a coprocessor, field-programmable gate array （FPGA） is the hardware computing processor accelerating the computing capacity of coraputers. To efficiently manage the hardware free resources for the placing of tasks on FPGA and take full advantage of the partially reconfigurable units, good utilization of chip resources is an important and necessary work. In this paper, a new method is proposed to find the complete set of maximal free resource rectangles based on the cross point of edge lines of running tasks on FPGA area, and the prove process is provided to make sure the correctness of this method.
文摘In this paper, the principle of multi-point forming (MPF) technique is presented. One of the most serious defects, wrinkling, during the multi-point forming process of a shallow rectangle cup is discussed by means of numerical simulation on the shallow rectangle cup forming process. The effects of thickness, material of sheet metal and the pressure of the blank holder are investigated. Based on the simulation results, the reasons and control methods of wrinkling are pointed out. Moreover, the experiment on the multi-point die forming of the shallow rectangle cup by the MPF machine is done to validate the efficiency of the numerical simulation, and the result proves that the application of an elastic cushion in the forming can restrain wrinkling efficiently.
文摘The problem of tiling rectangles by polyominoes generated large interest. A related one is the problem of tiling parallelograms by twisted polyominoes. Both problems are related with tilings of (skewed) quadrants by polyominoes. Indeed, if all tilings of a (skewed) quadrant by a tile set can be reduced to a tiling by congruent rectangles (parallelograms), this provides information about tilings of rectangles (parallelograms). We consider a class of tile sets in a square lattice appearing from arbitrary dissections of rectangles in two L-shaped polyominoes and from symmetries of these tiles about the first bisector. Only translations of the tiles are allowed in a tiling. If the sides of the dissected rectangle are coprime, we show the existence of tilings of all (skewed) quadrants that do not follow the rectangular (parallelogram) pattern. If one of the sides of the dissected rectangle is 2 and the other is odd, we also show tilings of rectangles by the tile set that do not follow the rectangular pattern. If one of the sides of the dissected rectangle is 2 and the other side is even, we show a new infinite family of tile sets that follows the rectangular pattern when tiling one of the quadrants. For this type of dis-section, we also show a new infinite family that does not follow the rectangular pattern when tiling rectangles. Finally, we investigate more general dissections of rectangles, with. Here we show infinite families of tile sets that follow the rectangular pattern for a quadrant and infinite families that do not follow the rectangular pattern for any quadrant. We also show, for infinite families of tile sets of this type, tilings of rectangles that do not follow the rectangular pattern.
基金support from the National Key R&D Program of China(Grant No.2020YFB1805901)the National Natural Science Foundation of China(Grant No.62105274)+1 种基金the Technology and Innovation Commission of Shenzhen Municipality(Grant No.JCYJ20210324133406018)the Research Grants Council,University Grants Committee of Hong Kong SAR(Grant No.PolyU15301022).
文摘The statistical dynamics of partially incoherent ultrafast lasers are complex and chaotic,which is significant for fundamental research and practical applications.We experimentally and theoretically reveal the statistical dynamics of the spectral evolutions and correlations in an incoherent noise-like rectangle pulse laser(NLRPL).Based on statistical histogram analysis,the probability distribution asymmetry of the spectral intensity fluctuation is decayed with the wavelength far away from the spectral peak due to the detection noise.The full-spectral correlation values indicate that the spectral similarity between two round trips is exponentially weakened as the round-trip offset increases.By studying the correlation map of spectral components,we find that the area of the high-correlation region is relevant to the pump power,which is reduced by increasing the pump power.The mutual information of the spectra demonstrates that two spectral components with symmetry about the spectral peak have a statistical dependence.Experimental observations and statistical properties can coincide well with theoretical numerical simulations.We reveal the pump-dependent spectral correlation of the NLRPL and provide multiple statistical methods for the characterizations of chaotic dynamics in incoherent light sources.
基金supported by the National Natural Science Foundation of China (Grant Nos. U20A2097,42075087, 91837310)the National Key Research and Development Program of China (Grant No. 2021YFC3000902)。
文摘Based on the TRMM dataset, this paper compares the applicability of the improved MCE(minimum circumscribed ellipse), MBR(minimum bounding rectangle), and DIA(direct indexing area) methods for rain cell fitting. These three methods can reflect the geometric characteristics of clouds and apply geometric parameters to estimate the real dimensions of rain cells. The MCE method shows a major advantage in identifying the circumference of rain cells. The circumference of rain cells identified by MCE in most samples is smaller than that identified by DIA and MBR, and more similar to the observed rain cells. The area of rain cells identified by MBR is relatively robust. For rain cells composed of many pixels(N> 20), the overall performance is better than that of MCE, but the contribution of MBR to the best identification results,which have the shortest circumference and the smallest area, is less than that of MCE. The DIA method is best suited to small rain cells with a circumference of less than 100 km and an area of less than 120 km^(2), but the overall performance is mediocre. The MCE method tends to achieve the highest success at any angle, whereas there are fewer “best identification”results from DIA or MBR and more of the worst ones in the along-track direction and cross-track direction. Through this comprehensive comparison, we conclude that MCE can obtain the best fitting results with the shortest circumference and the smallest area on behalf of the high filling effect for all sizes of rain cells.
文摘BACKGROUND For total laparoscopic distal gastrectomies for gastric cancer,the reconstruction method is critical to the clinical outcome of the procedure.However,which reconstruction technique is optimal remains controversial.We originally reported the augmented rectangle technique(ART)as a reconstruction option for total laparoscopic Billroth I reconstructions.Still,little is known about its effect on long-term outcomes,specifically the incidence of postgastrectomy syndrome and its impact on quality of life.AIM To analyze postgastrectomy syndrome and quality of life after ART using the Postgastrectomy Syndrome Assessment Scale-37(PGSAS-37)questionnaire.METHODS At Juntendo University,a total of 94 patients who underwent ART for Billroth I reconstruction with total laparoscopic distal gastrectomies for gastric cancer between July 2016 and March 2020 completed the PGSAS-37 questionnaire.Multidimensional analysis was performed,comparing those 94 ART cases from our institution(ART group)to 909 distal gastrectomy cases with a Billroth I reconstruction from other Japanese institutions who also completed the PGSAS-37 as part of a larger national database(PGSAS group).RESULTS Patients in the ART group had significantly better total symptom scores in all the symptom subscales(i.e.,esophageal reflux,abdominal pain,meal-related distress,indigestion,diarrhea,constipation,and dumping).The loss of body weight was marginally greater for those in the ART group than in the PGSAS group(-9.3%vs-7.9%,P=0.054).The ART group scored significantly lower in their dissatisfaction of ongoing symptoms,during meals,and with daily life.CONCLUSION ART for Billroth I reconstruction provided beneficial long-term results for postgastrectomy syndrome and quality of life in patients undergoing total laparoscopic distal gastrectomies for gastric cancer.
文摘The oil film thickness of oil hydrostatic guide with constant pressure supply based on capillary restrictor is greatly affected by load,and this kind of hydrostatic guide is usually applied to the machine tools with moderate load.The static and dynamic characteristics of the guide have been studied by using some theoretical,numerical and experimental approaches,and some methods and measures have been proposed to improve its performances.The hydrostatic guide based on progressive mengen(PM)flow controller is especially suitable for the heavy numerical control(NC)machine tools.However,few literatures about the research on the static and dynamic characteristics of the hydrostatic guides based on PM flow controller are reported.In this paper,the formulae are derived for analyzing the static and dynamic characteristics of hydrostatic guides with rectangle pockets and PM flow controller according to the theory of hydrostatic bearing.On the basis of the analysis of hydrostatic bearing with circular pocket,some equations are derived for solving the static pressure,volume pressure and squeezing pressure which influence the dynamic characteristics of hydrostatic guides with rectangle pocket.The function and the influencing factors of three pressures are clarified.The formulae of amplitude-frequency characteristics and dynamic stiffness of the hydrostatic guide system are derived.With the help of software MATLAB,programs are coded with C++language to simulate numerically the static and dynamic characteristics of the hydrostatic guide based on PM flow controller.The simulation results indicate that the sensitive oil volume between the outlet of the PM flow controller and the guide pocket has the greatest influence on the characteristics of the guide,and it should be reduced as small as possible when the field working condition is met.Choosing the oil with a greater viscosity is also helpful in improving the dynamic performance of hydrostatic guides.The research work has instructing significance for analyzing and designing the guide with PM flow controller.
基金the National Natural Science Foundation of China(Nos.U21A20117,U1560207 and 52003039)the National Key R&D Program of China(No.2017YFB0304402)+2 种基金the Fundamental Research Funds for the Central Universities(Nos.N2125018 and N2109001)the Liaoning Natural Science Foundation(No.2022-MS-365)the Liaoning Innovative Research Team in University(No.LT2017011).
文摘The internal quality inspection of the continuous casting billets is very important,and mis-inspection will seriously affect the subsequent production process.The UNet-VGG16 transfer learning model was used for semantic segmentation of the central shrinkage defects of the continuous casting billets.The automatic recognition accuracy of the central shrinkage defects of the continuous casting billets reaches more than 0.9.We use the minimum circumscribed rectangle to quantify the geometric dimensions such as length,width and area of the central shrinkage defects and use the threshold method to rate the central shrinkage defects of the continuous casting billets.The results show that all the testing images are rated correctly,and this method achieves the automatic recognition and intelligent analysis of the central shrinkage defects of the continuous casting billets.
文摘Helicopters are widely used in maritime Search and Rescue(SAR) missions. To ensure the success of SAR missions, search areas need to be carefully planned. With the development of computer technology and weather forecast technology, the survivors’ drift trajectories can be predicted more precisely, which strongly supports the planning of search areas for the rescue helicopter. However, the methods used to determine the search area based on the predicted drift trajectories are mainly derived from the continuous expansion of the area with the highest Probability of Containment(POC), which may lead to local optimal solutions and a decrease in the Probability of Success(POS), especially when there are several subareas with a high POC. To address this problem, this paper proposes a method based on a Minimum Bounding Rectangle and Kmeans clustering(MBRK). A silhouette coefficient is adopted to analyze the distribution of the survivors’ probable locations, which are divided into multiple clusters with K-means clustering. Then,probability maps are generated based on the minimum bounding rectangle of each cluster. By adding or subtracting one row or column of cells or shifting the planned search area, 12 search methods are used to generate the optimal search area starting from the cell with the highest POC in each probability map. Taking a real case as an example, the simulation experiment results show that the POS values obtained by the MBRK method are higher than those obtained by other methods,which proves that the MBRK method can effectively support the planning of search areas and that K-means clustering improves the POS of search plans.
基金The work of Jin Li was supported by National Natural Science Foundation of China(Grant No.11471195)China Postdoctoral Science Foundation(Grant No.2015T80703)+1 种基金Shan-dong Provincial Natural Science Foundation of China(Grant No.ZR2016JL006)Na-tional Natural Science Foundation of China(Grant No.11771398).
文摘In this paper,the classical composite middle rectangle rule for the computation of Cauchy principal value integral(the singular kernel 1=(x-s))is discussed.With the density function approximated only while the singular kernel is calculated analysis,then the error functional of asymptotic expansion is obtained.We construct a series to approach the singular point.An extrapolation algorithm is presented and the convergence rate of extrapolation algorithm is proved.At last,some numerical results are presented to confirm the theoretical results and show the efficiency of the algorithms.
文摘In many engineering applications, it is necessary to calculate the min-area encasing box of a circumscription. In this paper, an algorithm for generating the min-area rectangle encasing box, based on revolving angle, is investigated and hence put forward. The algorithm computes the areas of the outer rectangular bounds of a closed contour in different revolving angles θ by dispersing approach where 0< θ < π/2 because of the axial symmetry. It is very simple, straight forward and highly efficient. The complexity of its computing time reaches O(n·k ). Practical applications suggest its usefulness and efficiency.
基金Japan China Sasakawa Medical Fellowshipthe China Scholarship Council,No.201908310012。
文摘BACKGROUND Total laparoscopic distal gastrectomy(TLDG)is increasing due to some advantages over open surgery,which has generated interest in gastrointestinal surgeons.However,TLDG is technically demanding especially for lymphadenectomy and gastrointestinal reconstruction.During the course of training,trainee surgeons have less chances to perform open gastrectomy compared with that of senior surgeons.AIM To evaluate an appropriate,efficient and safe laparoscopic training procedures suitable for trainee surgeons.METHODS Ninety-two consecutive patients with gastric cancer who underwent TLDG plus Billroth I reconstruction using an augmented rectangle technique and involving trainees were reviewed.The trainees were taught a laparoscopic view of surgical anatomy,standard operative procedures and practiced essential laparoscopic skills.The TLDG procedure was divided into regional lymph node dissections and gastrointestinal reconstruction for analyzing trainee skills.Early surgical outcomes were compared between trainees and trainers to clarify the feasibility and safety of TLDG performed by trainees.Learning curves were used to assess the utility of our training system.RESULTS Five trainees performed a total of 52 TLDGs(56.5%),while 40 TLDGs were conducted by two trainers(43.5%).Except for depth of invasion and pathologic stage,there were no differences in clinicopathological characteristics.Trainers performed more D2 gastrectomies than trainees.The total operation time was significantly longer in the trainee group.The time spent during the lesser curvature lymph node dissection and the Billroth I reconstruction were similar between the two groups.No difference was found in postoperative complications between the two groups.The learning curve of the trainees plateaued after five TLDG cases.CONCLUSION Preparing trainees with a laparoscopic view of surgical anatomy,standard operative procedures and practice in essential laparoscopic skills enabled trainees to perform TLDG safely and feasibly.
文摘The gravity gradient is a secondary derivative of gravity potential,containing more high-frequency information of Earth’s gravity field.Gravity gradient observation data require deducting its prior and intrinsic parts to obtain more variational information.A model generated from a topographic surface database is more appropriate to represent gradiometric effects derived from near-surface mass,as other kinds of data can hardly reach the spatial resolution requirement.The rectangle prism method,namely an analytic integration of Newtonian potential integrals,is a reliable and commonly used approach to modeling gravity gradient,whereas its computing efficiency is extremely low.A modified rectangle prism method and a graphical processing unit(GPU)parallel algorithm were proposed to speed up the modeling process.The modified method avoided massive redundant computations by deforming formulas according to the symmetries of prisms’integral regions,and the proposed algorithm parallelized this method’s computing process.The parallel algorithm was compared with a conventional serial algorithm using 100 elevation data in two topographic areas(rough and moderate terrain).Modeling differences between the two algorithms were less than 0.1 E,which is attributed to precision differences between single-precision and double-precision float numbers.The parallel algorithm showed computational efficiency approximately 200 times higher than the serial algorithm in experiments,demonstrating its effective speeding up in the modeling process.Further analysis indicates that both the modified method and computational parallelism through GPU contributed to the proposed algorithm’s performances in experiments.
