Optical Orthogonal Frequency Division Multiplexing (OOFDM) has been proposed as a highly spectrum-efficient modulation technique, which can provide flexible spectrum assignment with fine granularity. In OOFDM-based fl...Optical Orthogonal Frequency Division Multiplexing (OOFDM) has been proposed as a highly spectrum-efficient modulation technique, which can provide flexible spectrum assignment with fine granularity. In OOFDM-based flexible optical networks, Routing and Spectrum Assignment (RSA) has become a key problem. However, widely used dynamic RSA schemes, such as Fixed Routing (FR) and K-shortest Paths (KSP) routing schemes, are not able to realize route computation based on the link state information, thus leading to poor blocking performance and inefficient resource utilization. To solve this problem, Adaptive Routing (AR) schemes, e.g., the Entire Path Searching (EPS) scheme, have been proposed recently. These schemes have low blocking probability; however, since their computational complexities are factorial, they are not suitable for use in real networks. In this paper, we propose a novel Spectrum-Scan Routing (SSR) scheme in dynamic flexible optical networks. To the best of our knowledge, SSR is the first polynomial-time AR scheme that can realize adaptive shortest-route computation. Simulation results show that our proposed SSR scheme has lower blocking probability and higher resource utilization compared with FR and EPS. Moreover, the worst-case computational complexity of SSR increases linearly with the network scale of the torus topologies, making it applicable to real networks.展开更多
为进一步研究现有基于对象的图像压缩技术,介绍两种基于对象的嵌入式小波图像编码算法——基于对象的集合分裂嵌入块(Object-Based SetPartitioned Embedded bloCK,OB-SPECK)编码算法和基于k-d树的二元集合分裂(Binary Set Splitting wi...为进一步研究现有基于对象的图像压缩技术,介绍两种基于对象的嵌入式小波图像编码算法——基于对象的集合分裂嵌入块(Object-Based SetPartitioned Embedded bloCK,OB-SPECK)编码算法和基于k-d树的二元集合分裂(Binary Set Splitting with k-d trees,BISK)编码算法,并进行比较分析.结果表明两种算法在集合分裂方案、对透明因数的处理方法及算法复杂度上有不同之处.在Matlab中进行的仿真实验表明,在对任意形状对象进行编码时,BISK编码算法在算法性能和图像压缩质量上较OB-SPECK编码算法更优.展开更多
To enhance the reverse blocking capability with low specific on-resistance,a novel vertical metal-oxidesemiconductor field-effect transistor（MOSFET） with a Schottky-drian（SD） and SD-connected semisuperjunctions（S...To enhance the reverse blocking capability with low specific on-resistance,a novel vertical metal-oxidesemiconductor field-effect transistor（MOSFET） with a Schottky-drian（SD） and SD-connected semisuperjunctions（SDD-semi-SJ）,named as SD-D-semi-SJ MOSFET is proposed and demonstrated by two-dimensional（2D） numerical simulations.The SD contacted with the n-pillar exhibits the Schottky-contact property,and that with the p-pillar the Ohmic-contact property.Based on these features,the SD-D-semi-SJ MOSFET could obviously overcome the great obstacle of the ineffectivity of the conventional superjunctions（SJ） or semisuperjunctions（semi-SJ） for the reverse applications and achieve a satisfactory trade-off between the reverse breakdown voltage（BV） and the specific on-resistance（R_（on）A）.For a given pillar width and n-drift thickness,there exists a proper range of n-drift concentration（N）,in which the SD-D-semi-SJ MOSFET could exhibit a better trade-off of R_（on）A-BV compared to the predication of SJ MOSFET in the forward applications.And what is much valuable,in this proper range of N,the desired BV and good trade-off could be achieved only by determining the pillar thickness,with the top assist layer thickness unchanged.Detailed analyses have been carried out to get physical insights into the intrinsic mechanism of R_（on）A-BV improvement in SD-D-semi-SJ MOSFET.These results demonstrate a great potential of SD-D-semi-SJ MOSFET in reverse applications.展开更多
基金supported in part by projects of National 863 Program under Grant No.2012AA011301National 973 Program under Grants No. 2010CB328203, No. 2010CB328205National Natural Science Foundation of China under Grant No. 61201188
文摘Optical Orthogonal Frequency Division Multiplexing (OOFDM) has been proposed as a highly spectrum-efficient modulation technique, which can provide flexible spectrum assignment with fine granularity. In OOFDM-based flexible optical networks, Routing and Spectrum Assignment (RSA) has become a key problem. However, widely used dynamic RSA schemes, such as Fixed Routing (FR) and K-shortest Paths (KSP) routing schemes, are not able to realize route computation based on the link state information, thus leading to poor blocking performance and inefficient resource utilization. To solve this problem, Adaptive Routing (AR) schemes, e.g., the Entire Path Searching (EPS) scheme, have been proposed recently. These schemes have low blocking probability; however, since their computational complexities are factorial, they are not suitable for use in real networks. In this paper, we propose a novel Spectrum-Scan Routing (SSR) scheme in dynamic flexible optical networks. To the best of our knowledge, SSR is the first polynomial-time AR scheme that can realize adaptive shortest-route computation. Simulation results show that our proposed SSR scheme has lower blocking probability and higher resource utilization compared with FR and EPS. Moreover, the worst-case computational complexity of SSR increases linearly with the network scale of the torus topologies, making it applicable to real networks.
文摘为进一步研究现有基于对象的图像压缩技术,介绍两种基于对象的嵌入式小波图像编码算法——基于对象的集合分裂嵌入块(Object-Based SetPartitioned Embedded bloCK,OB-SPECK)编码算法和基于k-d树的二元集合分裂(Binary Set Splitting with k-d trees,BISK)编码算法,并进行比较分析.结果表明两种算法在集合分裂方案、对透明因数的处理方法及算法复杂度上有不同之处.在Matlab中进行的仿真实验表明,在对任意形状对象进行编码时,BISK编码算法在算法性能和图像压缩质量上较OB-SPECK编码算法更优.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61574112,61334002,61306017,61474091,and 61574110)the Natural Science Basic Research Plan in Shaanxi Province of China(Grant No.605119425012)
文摘To enhance the reverse blocking capability with low specific on-resistance,a novel vertical metal-oxidesemiconductor field-effect transistor（MOSFET） with a Schottky-drian（SD） and SD-connected semisuperjunctions（SDD-semi-SJ）,named as SD-D-semi-SJ MOSFET is proposed and demonstrated by two-dimensional（2D） numerical simulations.The SD contacted with the n-pillar exhibits the Schottky-contact property,and that with the p-pillar the Ohmic-contact property.Based on these features,the SD-D-semi-SJ MOSFET could obviously overcome the great obstacle of the ineffectivity of the conventional superjunctions（SJ） or semisuperjunctions（semi-SJ） for the reverse applications and achieve a satisfactory trade-off between the reverse breakdown voltage（BV） and the specific on-resistance（R_（on）A）.For a given pillar width and n-drift thickness,there exists a proper range of n-drift concentration（N）,in which the SD-D-semi-SJ MOSFET could exhibit a better trade-off of R_（on）A-BV compared to the predication of SJ MOSFET in the forward applications.And what is much valuable,in this proper range of N,the desired BV and good trade-off could be achieved only by determining the pillar thickness,with the top assist layer thickness unchanged.Detailed analyses have been carried out to get physical insights into the intrinsic mechanism of R_（on）A-BV improvement in SD-D-semi-SJ MOSFET.These results demonstrate a great potential of SD-D-semi-SJ MOSFET in reverse applications.
