用动光弹方法研究隧道岩爆的爆破扰动机理

利用动态光弹性方法,以Lamb模型为依据,研究了不同荷载形式下,模型内应力波的传播、相互作用规律以及刻槽的拦截效应。实验结果与弹性动力学解答基本一致:(1)倾斜冲击荷载作用下,模型内传播的有P波、S波和Rayleigh波,其中P波和Rayleigh波对岩爆有突出贡献;(2)等差条纹图的分布规律,可以合理解释岩爆高发区段与开挖面的位置关系;(3)模型表面的刻槽,可以实现对Rayleigh波的大量拦截,说明隧道表面切槽的岩爆控制方法理论上是可行的。     

用自相关法确定VITA法的门限K

研究了用ＶＩＴＡ条件采样方法壁湍猝发的门限值与壁湍流猝发平均周期之间的关系,根据用壁湍流流向脉动速度自相关函数检测得到的壁湍流猝发平均周期,确定壁,湍猝发ＶＩＴＡ条件采样的门限值Ｋ。     

2.3 Wood pulp manufacturing and quality characteristics

Cellulose acetate being important in the fiber and textile industries is usually prepared from high quality cellulose such as cotton linters and wood pulps with an alpha cellulose content of more than 95%. In this section, therefore, wood pulps and cotton linters appropriate for cellulose acetate production were discussed in their chemical and physical properties so as to use them judiciously as natural raw materials for cellulose acetate production.     

Performance enhancement of optical burst switched networks

Optical burst switching (OBS) is an optical switching paradigm which offers a good tradeoff between the traditional optical circuit switching (OCS) and optical packet switching (OPS) since it has the relatively easy implementation of the first and the efficient bandwidth utilization of the second. Hence, OBS is a promising technology for the next generation optical Internet. A buffer-less OBS network can be implemented using ordinary optical communication equipment without the need for either wavelength converters or optical memories. In an OBS network, burst-loss performance is a critical concern. In OBS, the data-burst transmission is delayed by an offset time (relative to its burst control packet (BCP), or header) and the burst follows its header without waiting for an acknowledgment for resource reservation. Thus, a burst may be lost at an intermediate node due to contention, which is generally resolved according to the local routing and bandwidth information. The routing table maintained in each OBS node is generally pre-computed and fixed to forward the data bursts. Such a static forwarding feature might have limited efficiency to resolve contentions. Moreover, a burst may be lost and the network may be congested when a network element (e.g., fiber link) fails. In this paper, an efficient integrated scheme based on dynamic routing and burst segmentation has been proposed to improve reliability of data transport and network load balancing in optical burst switched networks. Simulation results demonstrate that the proposed approach reduces effectively blocking probability and hence contention. Further, it provides end-to-end throughput performance also. Hence, it establishes an appropriate tradeoff between loss rate and end-to-end throughput.     

Performance analysis of an improved burst-outputted model for an OBS core router

Differentiated probability outputted scheme (DPOS) is an improved burst-outputted paradigm in optical burst switching (OBS) core routers. In this paper, the blocking performance for multi-priority traffic in a DPOS applied OBS core router with limited buffers has been analyzed and discussed firstly. Several simulation results indicted that DPOS had a better performance in blocking than the outputted model presented in the previous work had. Besides, our proposed scheduling mechanism can supported the quality-of-service (QoS) efficiently for OBS networks.     

Comprehension of Jet Physics from the Analysis of the Gamma-Ray Burst Afterglow Parameter Distributions

The discovery of a short gamma-ray burst (GRB), GRB170817A, in association with a gravitational wave (GW) and a bright kilonova started a new era in the high-energy astrophysics. The observation of GRB170817A and more recently, GRB200826A and GRB211211A, a short and a long burst, respectively, with a possible kilonova, reinforce the concern about new ways of classification. For this reason, a new machine learning technique is applied to Swift-BAT data, searching for morphological similarities in the light curves. The resulting map is characterized by two distinct groups, although still correlated with standard T90 duration. Since a jet viewed off-axis could explain the emission from GRB170817A, the modeling of this kind of sources is of great importance. A public code called JetFit, based on the “boosted fireball” model, is applied to fit Swift-XRT afterglow light curves of short and long GRBs, with known red-shift, from 2005 to 2021. JetFit does not model the flaring activity. For this purpose, a new technique to remove the time flaring phases, is developed. This analysis provides a comprehensive study of the prompt and of the afterglow phase, trough the study of the best-fit parameters.     

An optimal burst assembly approach employing traffic shaping (OBATS) for OBS

Optical burst switching (OBS) aims at combining the strengths of packet and circuit switching and is considered as a promising technology for implementing the next generation optical Internet, required to cope with the rapid growth of Internet traffic and the increased deployment of new services. In this paper, an optimal burst assembly approach employing traffic shaping (OBATS) for OBS networks has been proposed in order to improve network performance in terms of reduced blocking probability, congestion control and better utilization of bandwidth. Particularly, the proposed scheme aims at reducing the average delay experienced by the packets during the burstification process in optical burst switched (OBS) networks, for a given average size of the bursts produced. Reducing the packet burstification delay, for a given average burst size, is essential for real-time applications; correspondingly, increasing the average burst size for a given packet burstification delay is important for reducing the number of bursts injected into the network and the associated overhead imposed on the core nodes. Simulation results show that the proposed burst assembly approach gives better network performance in terms of burst drop, resource contention and delay as compared to conventional burst assembly approaches.     

Congestion prevention for reliable OBS

It is known that Internet traffic exhibits a structural self-similarity over a wide range of time scales. Existing performance evaluation studies in optical burst switching (OBS) networks show high contention performance degradation in the nodes under correlated traffic. Due to its buffer-less nature, OBS efficiency can be reduced by resource contention leading to burst loss. Several methods have been proposed to address this problem, most of them relying on reactive mechanisms, which increase the complexity of core nodes, hampering scalability. In this paper to have congestion prevention, an efficient scheme incorporating delayed reservation decision has been proposed which not only offers reduction in resource contention by maintaining the same node complexity as that in general OBS networks with optical buffers but also provides improvement in system's throughput. Simulations show the proposed scheme has better performance than existing schemes in terms of burst loss probability.     

光突发与光电路混合交换边缘节点的设计与实现

提出了一种将光电路交换和光突发交换融合于同一网络的边缘节点设计方案.根据此方案，网络边缘节点能根据业务需求灵活选择交换方式.该方案在实际实验系统中进行了验证.结果表明，采用光电路交换方式，网络传输速率相对较快，而采用光突发交换方式，网络的带宽利用率更好.这两种交换方式共存于同一网络,一定程度上能提高网络的灵活性和适应性.     

具有氢键结构的有机材料及聚合物材料的压力诱导位移突变

利用纳米压痕技术研究了具有氢键结构的聚乙烯醇(PVA)和聚甲基丙烯酸甲酯(PMMA)的表面力学行为。与PMMA薄膜相比,在PVA薄膜的载荷-位移曲线上观察到了明显的位移突变现象。从结构差异分析可知,氢键诱导PVA薄膜产生了位移突变。为了证明结构中氢键与纳米压痕所获得的位移突变的相关性,制备了对苯二酚单晶并利用纳米压痕技术测试对苯二酚单晶的表面力学行为。结果表明,对苯二酚单晶具有氢键笼状结构,对苯二酚单晶的载荷-位移曲线载荷阶段以及保载小于临界载荷的位移-时间曲线均观察到了明显的位移突变和蠕变突变现象,并且载荷阶段的位移突变量随临界载荷的增加呈线性增加,同时位移突变还与加载速率相关。