In high-speed railway(HSR)wireless communication,the rapid channel changes and limited high-capacity access cause significant impact on the link performance.Meanwhile,the Doppler shift caused by high mobility leads to...In high-speed railway(HSR)wireless communication,the rapid channel changes and limited high-capacity access cause significant impact on the link performance.Meanwhile,the Doppler shift caused by high mobility leads to the inter-carrier interference.In this paper,we propose a reconfigurable intelligent surface(RIS)-assisted receive spatial modulation(SM)scheme based on the spatial-temporal correlated HSR Rician channel.The characteristics of SM and the phase shift adjustment of RIS are used to mitigate the performance degradation in high mobility scenarios.Considering the influence of channel spatial-temporal correlation and Doppler shift,the effects of different parameters on average bit error rate(BER)performance and upper bound of ergodic capacity are analyzed.Therefore,a joint antenna and RIS-unit selection algorithm based on the antenna removal method is proposed to increase the capacity performance of communication links.Numerical results show that the proposed RIS-assisted receive SM scheme can maintain high transmission capacity compared to the conventional HSR-SM scheme,whereas the degradation of BER performance can be compensated by arranging a large number of RIS-units.In addition,selecting more RIS-units has better capacity performance than activating more antennas in the low signal-to-noise ratio regions.展开更多
We present novel vector permutation and branch reduction methods to minimize the number of execution cycles for bit reversal algorithms.The new methods are applied to single instruction multiple data(SIMD)parallel imp...We present novel vector permutation and branch reduction methods to minimize the number of execution cycles for bit reversal algorithms.The new methods are applied to single instruction multiple data(SIMD)parallel implementation of complex data floating-point fast Fourier transform(FFT).The number of operational clock cycles can be reduced by an average factor of 3.5 by using our vector permutation methods and by 1.1 by using our branch reduction methods,compared with conventional im-plementations.Experiments on MPC7448(a well-known SIMD reduced instruction set computing processor)demonstrate that our optimal bit-reversal algorithm consistently takes fewer than two cycles per element in complex array operations.展开更多
Development of unconventional tight oil and gas reservoirs such as shale pays presents a huge challenge to the petroleum industry due to the naturally low permeability of shale formations and thus low productivity of ...Development of unconventional tight oil and gas reservoirs such as shale pays presents a huge challenge to the petroleum industry due to the naturally low permeability of shale formations and thus low productivity of oil and gas wells.Shale formations are also vulnerable to the contamination of the water in the drilling and completion fluids,which further reduces reservoir permeability.Although gas-drilling(drilling with gas)has been used to address the issue,several problems such as formation water influx,wellbore collapse,excessive gas volume requirement and hole cleaning in horizontal drilling,still hinder its application.A new technique called gas-lift drilling has recently been proposed to solve these problems,but the optimal design of drilling operation requires a thorough investigation of fluid flow field below the asymmetric drill bits for evaluating the fluid power needed to clean the bottom hole.Such an investigation is conducted in this work based on the Finite Element Method(FEM)implemented in an open source computational framework,FEniCS.Pressure and flow velocity fields were computed for three designs of drill bit face characterized by radial bit blades and one eccentric orifice of discharge.One of the designs is found superior over the other two because it generates relatively uniform flow velocities between blades and provides a balanced fluid power needed to clean all the bit teeth on each bit blade.To quantify the capability of borehole cleanup presented by three drill bit designs,the energy per unit volume is calculated in each region of drill bit and compared with the required value suggested by the literature.In addition,the developed FEM model under FEniCS framework provides engineers an accurate tool for optimizing drill bit design for efficiently gas-lift drilling unconventional tight oil and gas reservoirs.展开更多
A set of experimental apparatus on reverse circulation bit are developed, in order to lucubrate the mechanism of the new type reverse circulation bits, and the structure of the bits influencing the ability of taking c...A set of experimental apparatus on reverse circulation bit are developed, in order to lucubrate the mechanism of the new type reverse circulation bits, and the structure of the bits influencing the ability of taking core and carrying powder.Both the major structure of the equipment and the procession of experiment are described.展开更多
Reversible data hiding in encrypted image(RDHEI)is a widely used technique for privacy protection,which has been developed in many applications that require high confidentiality,authentication and integrity.Proposed R...Reversible data hiding in encrypted image(RDHEI)is a widely used technique for privacy protection,which has been developed in many applications that require high confidentiality,authentication and integrity.Proposed RDHEI methods do not allow high embedding rate while ensuring losslessly recover the original image.Moreover,the ciphertext form of encrypted image in RDHEI framework is easy to cause the attention of attackers.This paper proposes a reversible data hiding algorithm based on image camouflage encryption and bit plane compression.A camouflage encryption algorithm is used to transform a secret image into another meaningful target image,which can cover both secret image and encryption behavior based on“plaintext to plaintext”transformation.An edge optimization method based on prediction algorithm is designed to improve the image camouflage encryption quality.The reversible data hiding based bit-plane level compression,which can improve the redundancy of the bit plane by Gray coding,is used to embed watermark in the camouflage image.The experimental results also show the superior performance of the method in terms of embedding capacity and image quality.展开更多
Casing-while-drilling(CWD)with down the hole(DTH)hammer drilling technology has been widely used in unconsolidated formations,due to its advantages in protecting the borehole wall,excellent rock cuttings capacity,and ...Casing-while-drilling(CWD)with down the hole(DTH)hammer drilling technology has been widely used in unconsolidated formations,due to its advantages in protecting the borehole wall,excellent rock cuttings capacity,and fast penetration rate in hard rock.As an important component of the CWD system,the structure of the retractable drill bit needs not only to ensure to form stronger reverse circulation,but also to be expandable or retractable as needed,otherwise the drill bit cannot be lift and put down smoothly in the casing,and may lead to drilling accidents.This paper developed a new type of reverse circulation DTH hammer drill bit used for CWD drilling technology.The retractable performance of this type of drill bit is studied using ADAMS software.The results show that it is smoothly expandable and retractable as designed under the conditions of the weight of the bit(WOB)of 0.5–2.0 t and the rotation speed of 30–60 r/min.To investigate the reverse circulation effect of the drill bit,Fluent software was used to simulate the flow characteristic inside it.The simulation results indicated that it can form strong reverse circulation,and the entrainment ratio h can reach 9.5%.展开更多
By field experiment in Sandaozhuang W-Mo mining area in Luanchuan of Henan Province, the authors analyzed the Experimental result of reverse circulation bit on the basis of different structures and obtained the follow...By field experiment in Sandaozhuang W-Mo mining area in Luanchuan of Henan Province, the authors analyzed the Experimental result of reverse circulation bit on the basis of different structures and obtained the following conclusion: the design parameter of reverse circulation bit, the number, diameter and angle of the spurt hole can influence on the reverse circulation effect. The bit with inner spurt hole is better obviously than that one without inner spurt hole in reverse circulation, one or two right and the best choice of inner spurt hole is that the diameter is Φ8, the angle is 30° dip up and the suitable number is two to three.展开更多
By using fluent fluid engineer emulator software to simulate negative pressure formed inside the injector added in the reverse-circulation sampling drilling bit, at six angles of 15, 30, 45, 60, 75 and 90 degrees. The...By using fluent fluid engineer emulator software to simulate negative pressure formed inside the injector added in the reverse-circulation sampling drilling bit, at six angles of 15, 30, 45, 60, 75 and 90 degrees. The pressure distributing nephogram and the corresponding numerical value gotten compared with the experiment data received by an injector with 6 angles designed by emulation the conclusion. It has been found that the two values are coincident essentially. The article shows that using emulator technology to design optimizely is credible and simple. The cost is low and the design cycle is short compared with the method through experience and test.展开更多
The concept of dual image reversible data hiding（DIRDH） is the technique that can produce two camouflage images after embedding secret data into one original image.Moreover,not only can the secret data be extracted ...The concept of dual image reversible data hiding（DIRDH） is the technique that can produce two camouflage images after embedding secret data into one original image.Moreover,not only can the secret data be extracted from two camouflage images but also the original image can be recovered.To achieve high image quality,Lu et al.＇s method applied least-significant-bit（LSB） matching revisited to DIRDH.In order to further improve the image quality,the proposed method modifies LSB matching revisited rules and applies them to DIRDH.According to the experimental results,the image quality of the proposed method is better than that of Lu et al.＇s method.展开更多
The technical characteristics and operational principal of the reverse circulation DTH hammer drilling technology is integrated introduced in this paper. Using simulation technology to assist the drilling tool design,...The technical characteristics and operational principal of the reverse circulation DTH hammer drilling technology is integrated introduced in this paper. Using simulation technology to assist the drilling tool design, the optimum designed DTH hammer gets stable performance, and the bit has reverse circulation ability, and further more, it has already developed serial products. The reverse circulation DTH hammer drilling technique has been fully applied in field such as the geological core exploration in complex strata, water well drilling, and large diameter rock embedding piles drilling in hard rock, and obviously, it is achieved favorable economic and social benefits.展开更多
Air DTH hammer has been successfully applied in minor-caliber solid mineral exploration,water-well drilling and other drilling areas. In order to expand the applications of the technology,the authors further studied t...Air DTH hammer has been successfully applied in minor-caliber solid mineral exploration,water-well drilling and other drilling areas. In order to expand the applications of the technology,the authors further studied the principle and analyzed the mechanism of reverse circulation drilling technique with air DTH hammer to get the perfect assembles of equipments by optimizing working parameters. No parameter seemed more important than the air volume because it could maintain the working performance stability. The minimum air volume is related to the parameters such as depth and pressure,which was calculated under the actual conditions. It was solved for the air injection flow tables of the air DTH Hammer working at the different pressures. According to the data tables,operators could adjust the air volume to meet the demand on this technique,which had a realistic guiding significance. So it could build up a set of systematic and complete hi-technique.展开更多
A more efficient permutation algorithm which has less computer operation and better structure is presented here for radix-2 FFT(FHT). It can fasten the FFT and FHT efficiently when N becomes large.
If cuttings carrying performance is poor and cuttings removal is not in time during the drilling of horizontal wells,drilling cuttings will accumulate in the lower sections,leading to backing pressure,BHA binding and ...If cuttings carrying performance is poor and cuttings removal is not in time during the drilling of horizontal wells,drilling cuttings will accumulate in the lower sections,leading to backing pressure,BHA binding and even drill pipe sticking.In this paper,a new type of Helmholtz pulse grinding bits suitable for horizontal wells was designed based on the theory of Helmholtz oscillation chamber to generate pulse,jet pump and high pressure jet after the formation of cuttings beds was analyzed.In this type of bit,a high-speed pulse jet is used to assist rock breaking,a reverse jet is used to remove the cuttings at the bottom of the bit under negative pressure,and its inner grinding structure is used to reduce the particle size of cuttings.By using this bit,efficient cuttings removal and rock breaking will be both realized,the chip hold-down effect will be reduced and the cuttings beds in a horizontal well will be also removed.Then,the hydraulic models were established for a pulse generation device,an efficient rock breaking device and a reverse swabbing device,respectively.It is shown from the simulation results that the optimal resonance flowrate increases with the increase of the diameters of an inlet chamber and a feedback chamber and with the decrease of the diameter of a resonance chamber,and it is approximately in linear relationship with each factor.The optimal flowrate ratio of the reverse swabbing device increases first and then decreases with the increase of dimensionless flowrate ratio,and decreases with the increase of dimensionless area ratio.It is indicated from example analysis that the inherent frequency of Helmholtz oscillation chamber is 24.00 Hz,the optimal oscillation flowrate is 23.92 L/s and the optimal flowrate ratio is 0.59.Based on case studies,the accuracy of hydraulic models is verified.It is concluded that this new type of bits provides a new solution to the accumulation of cuttings beds.展开更多
自适应最高有效位预测(adaptive most significant bit prediction,AMP)是当前实现加密域可逆信息隐藏的一种重要算法。通过比较分块内首像素与其余像素,提取出公共最高有效位并用于像素预测,可节省空间嵌入秘密信息。然而,分块内首像...自适应最高有效位预测(adaptive most significant bit prediction,AMP)是当前实现加密域可逆信息隐藏的一种重要算法。通过比较分块内首像素与其余像素,提取出公共最高有效位并用于像素预测,可节省空间嵌入秘密信息。然而,分块内首像素与其他像素差异较大,会制约嵌入容量。为解决这个问题,本文将分块内嵌入数据时没有变化的像素聚集,构建为虚拟像素块。通过对虚拟像素块再次执行AMP算法,实现对当前方案嵌入容量的提升。为进一步增加虚拟像素块的数量,本文提出一种填充策略。以22的像素块为例,在分块嵌入容量足够大时,通过填充固定比特位增加像素相关性,使得嵌入过程中前两个像素保持不变,这样全部可用来构建虚拟块。因为填充策略构建T字段并提出新的32 bits像素结构,该结构能够提升像素相关性从而提升嵌入容量。通过在真实世界数据集上开展实验,结果表明本文所提算法相比当前的主流AMP算法,能够在保证可逆的前提下大幅提高嵌入容量。展开更多
基金supported in part by National Natural Science Foundation of China under Grant 62461024Jiangxi Provincial Natural Science Foundation of China under Grant 20224ACB202001.
文摘In high-speed railway(HSR)wireless communication,the rapid channel changes and limited high-capacity access cause significant impact on the link performance.Meanwhile,the Doppler shift caused by high mobility leads to the inter-carrier interference.In this paper,we propose a reconfigurable intelligent surface(RIS)-assisted receive spatial modulation(SM)scheme based on the spatial-temporal correlated HSR Rician channel.The characteristics of SM and the phase shift adjustment of RIS are used to mitigate the performance degradation in high mobility scenarios.Considering the influence of channel spatial-temporal correlation and Doppler shift,the effects of different parameters on average bit error rate(BER)performance and upper bound of ergodic capacity are analyzed.Therefore,a joint antenna and RIS-unit selection algorithm based on the antenna removal method is proposed to increase the capacity performance of communication links.Numerical results show that the proposed RIS-assisted receive SM scheme can maintain high transmission capacity compared to the conventional HSR-SM scheme,whereas the degradation of BER performance can be compensated by arranging a large number of RIS-units.In addition,selecting more RIS-units has better capacity performance than activating more antennas in the low signal-to-noise ratio regions.
文摘We present novel vector permutation and branch reduction methods to minimize the number of execution cycles for bit reversal algorithms.The new methods are applied to single instruction multiple data(SIMD)parallel implementation of complex data floating-point fast Fourier transform(FFT).The number of operational clock cycles can be reduced by an average factor of 3.5 by using our vector permutation methods and by 1.1 by using our branch reduction methods,compared with conventional im-plementations.Experiments on MPC7448(a well-known SIMD reduced instruction set computing processor)demonstrate that our optimal bit-reversal algorithm consistently takes fewer than two cycles per element in complex array operations.
基金This research was supported by the Open Fund(PLN201704)of the China State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation at the Southwest Petroleum University and the China National Natural Science Foundation Founding Nos.51874252,51534006 and 51674044.This research was also supported by the China Scholarship Council Founding No.201808510219.
文摘Development of unconventional tight oil and gas reservoirs such as shale pays presents a huge challenge to the petroleum industry due to the naturally low permeability of shale formations and thus low productivity of oil and gas wells.Shale formations are also vulnerable to the contamination of the water in the drilling and completion fluids,which further reduces reservoir permeability.Although gas-drilling(drilling with gas)has been used to address the issue,several problems such as formation water influx,wellbore collapse,excessive gas volume requirement and hole cleaning in horizontal drilling,still hinder its application.A new technique called gas-lift drilling has recently been proposed to solve these problems,but the optimal design of drilling operation requires a thorough investigation of fluid flow field below the asymmetric drill bits for evaluating the fluid power needed to clean the bottom hole.Such an investigation is conducted in this work based on the Finite Element Method(FEM)implemented in an open source computational framework,FEniCS.Pressure and flow velocity fields were computed for three designs of drill bit face characterized by radial bit blades and one eccentric orifice of discharge.One of the designs is found superior over the other two because it generates relatively uniform flow velocities between blades and provides a balanced fluid power needed to clean all the bit teeth on each bit blade.To quantify the capability of borehole cleanup presented by three drill bit designs,the energy per unit volume is calculated in each region of drill bit and compared with the required value suggested by the literature.In addition,the developed FEM model under FEniCS framework provides engineers an accurate tool for optimizing drill bit design for efficiently gas-lift drilling unconventional tight oil and gas reservoirs.
基金Supported by Jilin Science & Technology leading Development No. 20045033
文摘A set of experimental apparatus on reverse circulation bit are developed, in order to lucubrate the mechanism of the new type reverse circulation bits, and the structure of the bits influencing the ability of taking core and carrying powder.Both the major structure of the equipment and the procession of experiment are described.
基金supported in part by the National Key R&D Program of China(2019YFB1406504)the National Natural Science Foundation of China(U1836108,U1936216,62002197).
文摘Reversible data hiding in encrypted image(RDHEI)is a widely used technique for privacy protection,which has been developed in many applications that require high confidentiality,authentication and integrity.Proposed RDHEI methods do not allow high embedding rate while ensuring losslessly recover the original image.Moreover,the ciphertext form of encrypted image in RDHEI framework is easy to cause the attention of attackers.This paper proposes a reversible data hiding algorithm based on image camouflage encryption and bit plane compression.A camouflage encryption algorithm is used to transform a secret image into another meaningful target image,which can cover both secret image and encryption behavior based on“plaintext to plaintext”transformation.An edge optimization method based on prediction algorithm is designed to improve the image camouflage encryption quality.The reversible data hiding based bit-plane level compression,which can improve the redundancy of the bit plane by Gray coding,is used to embed watermark in the camouflage image.The experimental results also show the superior performance of the method in terms of embedding capacity and image quality.
基金the National Key Research and Development Program of China(No.2018YFC1505303).
文摘Casing-while-drilling(CWD)with down the hole(DTH)hammer drilling technology has been widely used in unconsolidated formations,due to its advantages in protecting the borehole wall,excellent rock cuttings capacity,and fast penetration rate in hard rock.As an important component of the CWD system,the structure of the retractable drill bit needs not only to ensure to form stronger reverse circulation,but also to be expandable or retractable as needed,otherwise the drill bit cannot be lift and put down smoothly in the casing,and may lead to drilling accidents.This paper developed a new type of reverse circulation DTH hammer drill bit used for CWD drilling technology.The retractable performance of this type of drill bit is studied using ADAMS software.The results show that it is smoothly expandable and retractable as designed under the conditions of the weight of the bit(WOB)of 0.5–2.0 t and the rotation speed of 30–60 r/min.To investigate the reverse circulation effect of the drill bit,Fluent software was used to simulate the flow characteristic inside it.The simulation results indicated that it can form strong reverse circulation,and the entrainment ratio h can reach 9.5%.
基金Project of China Geological Survey (No. 200120170130)
文摘By field experiment in Sandaozhuang W-Mo mining area in Luanchuan of Henan Province, the authors analyzed the Experimental result of reverse circulation bit on the basis of different structures and obtained the following conclusion: the design parameter of reverse circulation bit, the number, diameter and angle of the spurt hole can influence on the reverse circulation effect. The bit with inner spurt hole is better obviously than that one without inner spurt hole in reverse circulation, one or two right and the best choice of inner spurt hole is that the diameter is Φ8, the angle is 30° dip up and the suitable number is two to three.
基金Project of Science & Technology Development Guidance of Jilin Province (No.200405033)
文摘By using fluent fluid engineer emulator software to simulate negative pressure formed inside the injector added in the reverse-circulation sampling drilling bit, at six angles of 15, 30, 45, 60, 75 and 90 degrees. The pressure distributing nephogram and the corresponding numerical value gotten compared with the experiment data received by an injector with 6 angles designed by emulation the conclusion. It has been found that the two values are coincident essentially. The article shows that using emulator technology to design optimizely is credible and simple. The cost is low and the design cycle is short compared with the method through experience and test.
基金supported by MOST under Grants No.105-2410-H-468-010 and No.105-2221-E-468-019
文摘The concept of dual image reversible data hiding（DIRDH） is the technique that can produce two camouflage images after embedding secret data into one original image.Moreover,not only can the secret data be extracted from two camouflage images but also the original image can be recovered.To achieve high image quality,Lu et al.＇s method applied least-significant-bit（LSB） matching revisited to DIRDH.In order to further improve the image quality,the proposed method modifies LSB matching revisited rules and applies them to DIRDH.According to the experimental results,the image quality of the proposed method is better than that of Lu et al.＇s method.
基金Supported by the Fundamental Research Funds for Jilin University (No. 200903203)
文摘The technical characteristics and operational principal of the reverse circulation DTH hammer drilling technology is integrated introduced in this paper. Using simulation technology to assist the drilling tool design, the optimum designed DTH hammer gets stable performance, and the bit has reverse circulation ability, and further more, it has already developed serial products. The reverse circulation DTH hammer drilling technique has been fully applied in field such as the geological core exploration in complex strata, water well drilling, and large diameter rock embedding piles drilling in hard rock, and obviously, it is achieved favorable economic and social benefits.
基金supported by the project of the feasibility study on air reverse circulation drilling system,research foundation for out standingteachers,Jilin University(No.2006220100003435)
文摘Air DTH hammer has been successfully applied in minor-caliber solid mineral exploration,water-well drilling and other drilling areas. In order to expand the applications of the technology,the authors further studied the principle and analyzed the mechanism of reverse circulation drilling technique with air DTH hammer to get the perfect assembles of equipments by optimizing working parameters. No parameter seemed more important than the air volume because it could maintain the working performance stability. The minimum air volume is related to the parameters such as depth and pressure,which was calculated under the actual conditions. It was solved for the air injection flow tables of the air DTH Hammer working at the different pressures. According to the data tables,operators could adjust the air volume to meet the demand on this technique,which had a realistic guiding significance. So it could build up a set of systematic and complete hi-technique.
文摘A more efficient permutation algorithm which has less computer operation and better structure is presented here for radix-2 FFT(FHT). It can fasten the FFT and FHT efficiently when N becomes large.
文摘If cuttings carrying performance is poor and cuttings removal is not in time during the drilling of horizontal wells,drilling cuttings will accumulate in the lower sections,leading to backing pressure,BHA binding and even drill pipe sticking.In this paper,a new type of Helmholtz pulse grinding bits suitable for horizontal wells was designed based on the theory of Helmholtz oscillation chamber to generate pulse,jet pump and high pressure jet after the formation of cuttings beds was analyzed.In this type of bit,a high-speed pulse jet is used to assist rock breaking,a reverse jet is used to remove the cuttings at the bottom of the bit under negative pressure,and its inner grinding structure is used to reduce the particle size of cuttings.By using this bit,efficient cuttings removal and rock breaking will be both realized,the chip hold-down effect will be reduced and the cuttings beds in a horizontal well will be also removed.Then,the hydraulic models were established for a pulse generation device,an efficient rock breaking device and a reverse swabbing device,respectively.It is shown from the simulation results that the optimal resonance flowrate increases with the increase of the diameters of an inlet chamber and a feedback chamber and with the decrease of the diameter of a resonance chamber,and it is approximately in linear relationship with each factor.The optimal flowrate ratio of the reverse swabbing device increases first and then decreases with the increase of dimensionless flowrate ratio,and decreases with the increase of dimensionless area ratio.It is indicated from example analysis that the inherent frequency of Helmholtz oscillation chamber is 24.00 Hz,the optimal oscillation flowrate is 23.92 L/s and the optimal flowrate ratio is 0.59.Based on case studies,the accuracy of hydraulic models is verified.It is concluded that this new type of bits provides a new solution to the accumulation of cuttings beds.
文摘自适应最高有效位预测(adaptive most significant bit prediction,AMP)是当前实现加密域可逆信息隐藏的一种重要算法。通过比较分块内首像素与其余像素,提取出公共最高有效位并用于像素预测,可节省空间嵌入秘密信息。然而,分块内首像素与其他像素差异较大,会制约嵌入容量。为解决这个问题,本文将分块内嵌入数据时没有变化的像素聚集,构建为虚拟像素块。通过对虚拟像素块再次执行AMP算法,实现对当前方案嵌入容量的提升。为进一步增加虚拟像素块的数量,本文提出一种填充策略。以22的像素块为例,在分块嵌入容量足够大时,通过填充固定比特位增加像素相关性,使得嵌入过程中前两个像素保持不变,这样全部可用来构建虚拟块。因为填充策略构建T字段并提出新的32 bits像素结构,该结构能够提升像素相关性从而提升嵌入容量。通过在真实世界数据集上开展实验,结果表明本文所提算法相比当前的主流AMP算法,能够在保证可逆的前提下大幅提高嵌入容量。
