While cable-driven snake robots are promising in exploring confined spaces, their hyper-redundancy makes the collision-free motion planning difficult. In this paper, by combining the prediction lookup and interpolatio...While cable-driven snake robots are promising in exploring confined spaces, their hyper-redundancy makes the collision-free motion planning difficult. In this paper, by combining the prediction lookup and interpolation algorithms, we present a new path following method for cable-driven snake robots to high-efficiently slither into complex terrains along a desired path. In our method, we first discretize the desired path into points, and develop the prediction lookup algorithm to efficiently find the points matched with joints of the robot. According to geometric relations between the prediction lookup results and link length of the robot, we develop the interpolation algorithm to reduce the tracking errors caused by the discretization. Finally, simulations and experiments of inspections in two confined spaces including the obstacle array and pipe tank system are performed on our custom-built 25 degree of freedoms(DOFs) cable-driven snake robot. The results demonstrate that the presented method can successfully navigate our snake robot into confined spaces with high computational efficiency and good accuracy, which well verifies effectiveness of our development.展开更多
Two different methods from graphic processing unit （GPU） and central processing unit （CPU） are proposed to suitably optimize look-up table algorithms of computer generated holography （CGH）. The numerical simula-...Two different methods from graphic processing unit （GPU） and central processing unit （CPU） are proposed to suitably optimize look-up table algorithms of computer generated holography （CGH）. The numerical simula- tions and experimental results show that we can reconstruct a good quality object. The computation of CGH for a three-dimensional （3D） dynamic holographic display can also be sped up by programming with our proposed method. It can optimize both file loading and the inline calculation process. The phase-only CGH with gigabyte data for reconstructing 10 MB object samplings is generated. In addition, the proposed method effectively re- duced time costs of loading and writing offline tables on a CPU. It is believed the proposed method can provide high speed and huge data CGH for 3D dynamic holographic displays in the near future.展开更多
为了能够实时、高效地获取Twitter数据,在分析了传统采集方法的缺陷后,提出了基于Twitter List API和Lookup API的用户数据采集方案。该方案通过对用户进行分类,进而精确控制API的调用频率。经在超过26万Twitter用户和600万条消息的一...为了能够实时、高效地获取Twitter数据,在分析了传统采集方法的缺陷后,提出了基于Twitter List API和Lookup API的用户数据采集方案。该方案通过对用户进行分类,进而精确控制API的调用频率。经在超过26万Twitter用户和600万条消息的一系列实验证明,通过两套方案的结合可以实现Twitter用户数据高效实时的获取。展开更多
White-box cryptography is critical in a communication system to protect the secret key from being disclosed in a cryptographic algorithm code implementation.The stream cipher is a main dataflow encryption approach in ...White-box cryptography is critical in a communication system to protect the secret key from being disclosed in a cryptographic algorithm code implementation.The stream cipher is a main dataflow encryption approach in mobile communication.However,research work on white-box cryptographic implementation for stream cipher is rare.A new white-box Zu Chongzhi-128(ZUC-128)cryptographic implementation algorithm named WBZUC was proposed.WBZUC adopts lookup table and random coding in the non-linear function to make the intermediate value chaotic without changing the final encryption result.Thus,the WBZUC algorithm’s security gets improved compared with the original ZUC-128 algorithm.As for the efficiency,a test experiment on WBZUC shows that the average speed of key generation,encryption,and decryption can reach at 33.74 kbit/s,23.31 kbit/s,24.06 kbit/s respectively.Despite its running speed is relatively a bit lower than original ZUC-128 algorithm,WBZUC can provide better security and comprehensive performance in mobile communication system environment.展开更多
Maintaining a semantic cache of materialized XPath views inside or outside the database is a novel, feasible and efficient approach to facilitating XML query processing. However, most of the existing approaches incur ...Maintaining a semantic cache of materialized XPath views inside or outside the database is a novel, feasible and efficient approach to facilitating XML query processing. However, most of the existing approaches incur the following disadvantages： 1） they cannot discover enough potential cached views sufficiently to effectively answer subsequent queries; or 2） they are inefficient for view selection due to the complexity of XPath expressions. In this paper, we propose SCEND, an effective Semantic Cache based on dEcompositioN and Divisibility, to exploit the XPath query/view answerability. The contributions of this paper include： 1） a novel technique of decomposing complex XPath queries into some much simpler ones, which can facilitate discovering more potential views to answer a new query than the existing methods and thus can adequately exploit the query/view answerability; 2） an efficient view-section method by checking the divisibility between two positive numbers assigned to queries and views; 3） a cache-replacement approach to further enhancing the query/view answerability; 4） an extensive experimental study which demonstrates that our approach achieves higher performance and outperforms the existing state-of-the-art alternative methods significantly.展开更多
To compensate for nonlinear distortion introduced by RF power amplifiers （PAs） with memory effects, two correlated models, namely an extended memory polynomial （EMP） model and a memory lookup table （LUT） model, ...To compensate for nonlinear distortion introduced by RF power amplifiers （PAs） with memory effects, two correlated models, namely an extended memory polynomial （EMP） model and a memory lookup table （LUT） model, are proposed for predistorter design. Two adaptive digital predistortion （ADPD） schemes with indirect learning architecture are presented. One adopts the EMP model and the recursive least square （RLS） algorithm, and the other utilizes the memory LUT model and the least mean square （LMS） algorithm. Simulation results demonstrate that the EMP-based ADPD yields the best linearization performance in terms of suppressing spectral regrowth. It is also shown that the ADPD based on memory LUT makes optimum tradeoff between performance and computational complexity.展开更多
In this paper,it has proposed a realtime implementation of low-density paritycheck(LDPC) decoder with less complexity used for satellite communication on FPGA platform.By adopting a(2048.4096)irregular quasi-cyclic(QC...In this paper,it has proposed a realtime implementation of low-density paritycheck(LDPC) decoder with less complexity used for satellite communication on FPGA platform.By adopting a(2048.4096)irregular quasi-cyclic(QC) LDPC code,the proposed partly parallel decoding structure balances the complexity between the check node unit(CNU) and the variable node unit(VNU) based on min-sum(MS) algorithm,thereby achieving less Slice resources and superior clock performance.Moreover,as a lookup table(LUT) is utilized in this paper to search the node message stored in timeshare memory unit,it is simple to reuse and save large amount of storage resources.The implementation results on Xilinx FPGA chip illustrate that,compared with conventional structure,the proposed scheme can achieve at last 28.6%and 8%cost reduction in RAM and Slice respectively.The clock frequency is also increased to 280 MHz without decoding performance deterioration and convergence speed reduction.展开更多
A halftone watermarking method of high quality, robustness, and capacity flexibility is presented in this paper. An objective halftone image quality evaluation method based on the human visual system obtained by a lea...A halftone watermarking method of high quality, robustness, and capacity flexibility is presented in this paper. An objective halftone image quality evaluation method based on the human visual system obtained by a least-mean-square algorithm is also introduced. In the encoder, the kernels-alternated error diffusion （KAEDF） is applied. It is able to maintain the computational complexity at the same level as ordinary error diffusion. Compared with Hel-Or using ordered dithering, the proposed KAEDF yields a better image quality through using error diffusion. We also propose a weighted lookup table （WLUT） in the decoder instead of lookup table （LUT）, as proposed by Pei and Guo, so as to achieve a higher decoded rate. As the experimental results demonstrate, this technique is able to guard against degradation due to tampering, cropping, rotation, and print-and-scan processes in error-diffused halftone images.展开更多
In this letter, we present a scheme generating OFDM signals in optical domain instead of electrical domain by transmitting subcarrier signals with multiple LEDs. According to the simulation, this scheme can effectivel...In this letter, we present a scheme generating OFDM signals in optical domain instead of electrical domain by transmitting subcarrier signals with multiple LEDs. According to the simulation, this scheme can effectively eliminate signal degradation caused by the high peak-to-average power ratio of OFDM signals in traditional transmitter. Computational complexity in digital part of the transmitter can be reduced by using look-uo table. Receiver will stay unchanged.展开更多
Routing technology has been forced to evolve towards higher capacity and per port packet processing speed. The ability to achieve high forwarding speed is due to either software or hardware technology. TCAM (Ternary C...Routing technology has been forced to evolve towards higher capacity and per port packet processing speed. The ability to achieve high forwarding speed is due to either software or hardware technology. TCAM (Ternary Content Addressable Memory) provides a performance advantage over other software or hardware search algorithms, often resulting in an order of magnitude reduction of search time. But slow updates may affect the performance of TCAM based routing lookup. So the key is to design a table management algorithm, which supports high speed updates in TCAMs. This paper presented three table management algorithms, and then compared their performance. Finally, the optimal one after comparing was given.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.51435010,and 91848204)。
文摘While cable-driven snake robots are promising in exploring confined spaces, their hyper-redundancy makes the collision-free motion planning difficult. In this paper, by combining the prediction lookup and interpolation algorithms, we present a new path following method for cable-driven snake robots to high-efficiently slither into complex terrains along a desired path. In our method, we first discretize the desired path into points, and develop the prediction lookup algorithm to efficiently find the points matched with joints of the robot. According to geometric relations between the prediction lookup results and link length of the robot, we develop the interpolation algorithm to reduce the tracking errors caused by the discretization. Finally, simulations and experiments of inspections in two confined spaces including the obstacle array and pipe tank system are performed on our custom-built 25 degree of freedoms(DOFs) cable-driven snake robot. The results demonstrate that the presented method can successfully navigate our snake robot into confined spaces with high computational efficiency and good accuracy, which well verifies effectiveness of our development.
基金supported by the National High Technology Research and Development Program of China(No.2015AA015905)the National Basic Research Program of China(Nos.2013CB328801 and2013CB328806)the National Natural Science Founding of China(Nos.61420106014 and 61235002)
文摘Two different methods from graphic processing unit （GPU） and central processing unit （CPU） are proposed to suitably optimize look-up table algorithms of computer generated holography （CGH）. The numerical simula- tions and experimental results show that we can reconstruct a good quality object. The computation of CGH for a three-dimensional （3D） dynamic holographic display can also be sped up by programming with our proposed method. It can optimize both file loading and the inline calculation process. The phase-only CGH with gigabyte data for reconstructing 10 MB object samplings is generated. In addition, the proposed method effectively re- duced time costs of loading and writing offline tables on a CPU. It is believed the proposed method can provide high speed and huge data CGH for 3D dynamic holographic displays in the near future.
文摘为了能够实时、高效地获取Twitter数据,在分析了传统采集方法的缺陷后,提出了基于Twitter List API和Lookup API的用户数据采集方案。该方案通过对用户进行分类,进而精确控制API的调用频率。经在超过26万Twitter用户和600万条消息的一系列实验证明,通过两套方案的结合可以实现Twitter用户数据高效实时的获取。
基金supported by the Beijing Natural Science Foundation(4232034)the Fundamental Research Funds for the Central Universities(328202222)the“Communication Engineering”and“Electronic Information Engineering”National First-Class Undergraduate Major Construction Project。
文摘White-box cryptography is critical in a communication system to protect the secret key from being disclosed in a cryptographic algorithm code implementation.The stream cipher is a main dataflow encryption approach in mobile communication.However,research work on white-box cryptographic implementation for stream cipher is rare.A new white-box Zu Chongzhi-128(ZUC-128)cryptographic implementation algorithm named WBZUC was proposed.WBZUC adopts lookup table and random coding in the non-linear function to make the intermediate value chaotic without changing the final encryption result.Thus,the WBZUC algorithm’s security gets improved compared with the original ZUC-128 algorithm.As for the efficiency,a test experiment on WBZUC shows that the average speed of key generation,encryption,and decryption can reach at 33.74 kbit/s,23.31 kbit/s,24.06 kbit/s respectively.Despite its running speed is relatively a bit lower than original ZUC-128 algorithm,WBZUC can provide better security and comprehensive performance in mobile communication system environment.
基金supported by the National Natural Science Foundation of China under Grant No.60873065the National High Technology Research and Development 863 Program of China under Grant Nos.2007AA01Z152 and 2009AA011906the National Basic Research 973 Program of China under Grant No.2006CB303103.
文摘Maintaining a semantic cache of materialized XPath views inside or outside the database is a novel, feasible and efficient approach to facilitating XML query processing. However, most of the existing approaches incur the following disadvantages： 1） they cannot discover enough potential cached views sufficiently to effectively answer subsequent queries; or 2） they are inefficient for view selection due to the complexity of XPath expressions. In this paper, we propose SCEND, an effective Semantic Cache based on dEcompositioN and Divisibility, to exploit the XPath query/view answerability. The contributions of this paper include： 1） a novel technique of decomposing complex XPath queries into some much simpler ones, which can facilitate discovering more potential views to answer a new query than the existing methods and thus can adequately exploit the query/view answerability; 2） an efficient view-section method by checking the divisibility between two positive numbers assigned to queries and views; 3） a cache-replacement approach to further enhancing the query/view answerability; 4） an extensive experimental study which demonstrates that our approach achieves higher performance and outperforms the existing state-of-the-art alternative methods significantly.
文摘To compensate for nonlinear distortion introduced by RF power amplifiers （PAs） with memory effects, two correlated models, namely an extended memory polynomial （EMP） model and a memory lookup table （LUT） model, are proposed for predistorter design. Two adaptive digital predistortion （ADPD） schemes with indirect learning architecture are presented. One adopts the EMP model and the recursive least square （RLS） algorithm, and the other utilizes the memory LUT model and the least mean square （LMS） algorithm. Simulation results demonstrate that the EMP-based ADPD yields the best linearization performance in terms of suppressing spectral regrowth. It is also shown that the ADPD based on memory LUT makes optimum tradeoff between performance and computational complexity.
文摘In this paper,it has proposed a realtime implementation of low-density paritycheck(LDPC) decoder with less complexity used for satellite communication on FPGA platform.By adopting a(2048.4096)irregular quasi-cyclic(QC) LDPC code,the proposed partly parallel decoding structure balances the complexity between the check node unit(CNU) and the variable node unit(VNU) based on min-sum(MS) algorithm,thereby achieving less Slice resources and superior clock performance.Moreover,as a lookup table(LUT) is utilized in this paper to search the node message stored in timeshare memory unit,it is simple to reuse and save large amount of storage resources.The implementation results on Xilinx FPGA chip illustrate that,compared with conventional structure,the proposed scheme can achieve at last 28.6%and 8%cost reduction in RAM and Slice respectively.The clock frequency is also increased to 280 MHz without decoding performance deterioration and convergence speed reduction.
基金supported by National Science Council under Grants No. NSC 99-2631-H-011-001
文摘A halftone watermarking method of high quality, robustness, and capacity flexibility is presented in this paper. An objective halftone image quality evaluation method based on the human visual system obtained by a least-mean-square algorithm is also introduced. In the encoder, the kernels-alternated error diffusion （KAEDF） is applied. It is able to maintain the computational complexity at the same level as ordinary error diffusion. Compared with Hel-Or using ordered dithering, the proposed KAEDF yields a better image quality through using error diffusion. We also propose a weighted lookup table （WLUT） in the decoder instead of lookup table （LUT）, as proposed by Pei and Guo, so as to achieve a higher decoded rate. As the experimental results demonstrate, this technique is able to guard against degradation due to tampering, cropping, rotation, and print-and-scan processes in error-diffused halftone images.
基金supported by the National Key Basic Research Program of China(No.2013CB329201)the National High Technology Research and Development Program of China(No.2013AA013601)
文摘In this letter, we present a scheme generating OFDM signals in optical domain instead of electrical domain by transmitting subcarrier signals with multiple LEDs. According to the simulation, this scheme can effectively eliminate signal degradation caused by the high peak-to-average power ratio of OFDM signals in traditional transmitter. Computational complexity in digital part of the transmitter can be reduced by using look-uo table. Receiver will stay unchanged.
文摘Routing technology has been forced to evolve towards higher capacity and per port packet processing speed. The ability to achieve high forwarding speed is due to either software or hardware technology. TCAM (Ternary Content Addressable Memory) provides a performance advantage over other software or hardware search algorithms, often resulting in an order of magnitude reduction of search time. But slow updates may affect the performance of TCAM based routing lookup. So the key is to design a table management algorithm, which supports high speed updates in TCAMs. This paper presented three table management algorithms, and then compared their performance. Finally, the optimal one after comparing was given.
