Effect of chemical functionalization on the mechanical properties of polypropylene hollow fiber membranes

Chemical treatment of polymeric hollow fiber membranes (HFMs) is used to prepare their exterior surfaces for coatings. Typical treatments can cleave both C? C and C? H bonds of polypropylene, leading to lower mechanical strength of the fibers. This study evaluated the yield strength, maximum strain, ultimate tensile strength, and burst strength of HFMs treated with each of three common oxidizing reagents: ozone as a gas phase system, aqueous solutions of potassium persulfate, and ammonium persulfate for liquid phase systems. The yield strength and ultimate tensile strength of HFMs decreased continuously with increasing ozonation time. Batch treatments with aqueous oxidizing systems showed limiting values of the yield and ultimate tensile strengths with time. Swelling the hollow fibers with methanol prior to oxidation caused less reduction of the mechanical properties after persulfate treatment. Fibers pretreated with methanol showed lower losses of mechanical properties strength with aqueous oxidation systems. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1366–1373     

An efficient scheme for optimizing channel utilization in OBS networks

Optical burst switching (OBS) is an emerging technology that allows variable size data bursts to be transported directly over DWDM links. In order to make OBS a viable solution, the wavelength scheduling algorithms need to be able to utilize the available wavelengths efficiently, while being able to operate fast enough to keep up with the burst incoming rate. Unfortunately, horizon scheduling cannot utilize the voids created by previously scheduled bursts, resulting in low bandwidth utilization. To date, Min-SV is the fastest scheduling algorithm that can schedule wavelengths efficiently. However, its complexity is O (log m) and it requires 10 log (m) memory accesses to schedule a single burst. This means that it can take upto several microseconds for each burst request, which is still too slow to make it a practical solution for OBS deployment. In this paper, an efficient scheme has been proposed for optimizing channel utilization in OBS networks. In the proposed approach, a burst is represented by an interval of time. The process of scheduling a number of bursts, thus, turns to be a process of fitting a set of the corresponding time intervals on a channel time line that represents a channel-time resource. By doing so, the scheduling process can be formulated as a combinatorial optimization problem. Then, graph theory is applied to schedule as many non-overlapping intervals as possible onto the channel time line. The underlying concept of the proposed scheduling scheme is that of briefly delaying the scheduling of a burst so that a much better decision can be made about a number of bursts all-together. This scheme is shown, through simulations, to improve performance in terms of burst loss probability, channel utilization, fairness-control and data throughput over existing schemes. Thus the proposed scheme is well suited for high performance networks in terms of reliability.     

基于GMPLS的光突发交换网络传输性能分析

针对基于多协议标记交换的光突发交换网络在组网过程中存在传输性能劣化的问题,采用最坏值的方法,从典型光交叉节点的串扰特性入手,分析推导了网络中多个节点级联后同频串扰对传输性能的影响,并通过仿真进行验证.分析结果表明,核心节点级联产生的串扰累积是导致该网络传输性能劣化的重要因素.     

Extending the Redshift-Distance Relation in Cosmological General Relativity to Higher Redshifts

The redshift-distance modulus relation, the Hubble Diagram, derived from Cosmological General Relativity has been extended to arbitrarily large redshifts. Numerical methods were employed and a density function was found that results in a valid solution of the field equations at all redshifts. The extension has been compared to 302 type Ia supernova data as well as to 69 Gamma-ray burst data. The latter however do not truly represent a ‘standard candle’ as the derived distance moduli are not independent of the cosmology used. Nevertheless the analysis shows a good fit can be achieved without the need to assume the existence of dark matter. The Carmelian theory is also shown to describe a universe that is always spatially flat. This results from the underlying assumption of the energy density of a cosmological constant Ω_Λ=1, the result of vacuum energy. The curvature of the universe is described by a spacevelocity metric where the energy content of the curvature at any epoch is Ω _K =Ω_Λ−Ω=1−Ω, where Ω is the matter density of the universe. Hence the total density is always Ω _K +Ω=1.     

基于延迟抢占的突发竞争解决策略

在光突发交换网络中, 将竞争突发送入光纤延迟线(FDLs)缓存以避免丢弃被认为是一种便捷、有效的竞争解决方案。基于“提前预留”模型, 提出采用延迟抢占(DP)的方式来实现突发的竞争解决, 比较了全延迟抢占与部分延迟抢占机制的阻塞性能。为支持区分服务, 开展了两优先级系统中延迟抢占机制的研究, 建立了适用于两优先级系统的阻塞分析模型, 并对不同配比条件下延迟抢占机制的阻塞及延迟性能进行了仿真分析。仿真结果表明, 延迟抢占机制有效地保证了高优先级突发的低阻塞要求, 与低优先级突发相比, 其突发阻塞率要低约2个数量级。此外, 由于FDL的长度固定, 数据突发的时延要求也得到了有效保障, 流量载荷ρ=1.0时, 高优先级突发的平均延迟仅为10 μs。     

能识别弹丸飞行方向的弹丸空间炸点三维坐标测试方法

针对现有测量装置在测量近炸引信弹丸空间炸点三维坐标时存在的不足,提出了一种采用6光幕阵列配合火焰探测器测量弹丸空间炸点的三维坐标测试方法.提出的方法包含两台多光幕天幕靶、一台空间炸点火焰探测器和一台多路数据采集仪.两台多光幕天幕靶的6套光路和光电转换部件在空间构成6光幕探测阵列,当弹丸穿过6个探测光幕时,多路数据采集仪...     

大脉冲热负荷下HL-2A偏滤器靶板的热分析

HL－2A安装完成后,将以ASDEX最终的运行参数水平进行工程调试。本文研究了,在仅有欧姆加热和3.5MW中性束注入条件下,当HL－2A发生大不稳定性或巨ELMs爆发时,有水冷却和辐射冷却两种情况下不同板材料偏滤器板的温升和冷却时间。     

Blocking improvement for high priority in differentiated OBS networks through preemption and buffer-limitation

Delay preemption that combines the techniques of preemption and small buffers is an efficient solution for burst contention. However, due to the phenomenon of over-usage on buffer, the low-loss demand of high priority is not ensured especially in high traffic states. In this article, to improve the blocking of delay preemption, we propose a modified scheme named limited delay preemption based priority (limited-DPP) that constrains the buffered right of low priority within the moderate and high traffic states. To validate the efficiency of limited-DPP, the comprehensive analysis and simulation are performed in terms of loss and buffering time.     

基于流量门限的提前预留竞争解决机制(英文)

基于小尺寸缓存的提前预留机制是有效的竞争解决方案.为支持区分服务,本文研究了两优先级提前预留机制的阻塞模型,分析了变化缓存尺寸与载荷比率条件下光突发交换网络核心节点的阻塞性能.为降低两优先级提前预留机制的突发丢弃率,提出一种基于流量门限的提前预留机制.数值分析确定了合理的缓存尺寸与流量门限,实现了高、低优先级间的缓存使用平衡.仿真结果表明:与原有提前预留机制相比,基于流量门限的提前预留机制保持了全流量状态范围内的阻塞性能,并明显降低了中、低流量状态内的突发丢弃率.     

点火位置对氢气-空气预混气体泄爆过程的影响

利用高速纹影和压力测试系统对不同点火位置及不同破膜压力条件下氢气-空气预混气的泄爆特性进行研究。研究结果表明:在所有情况下,中心点火时火焰传播速率和面积最大,产生了最大的内部压力峰值,尾端点火时火焰传播速率和面积次之,产生的内部压力峰值也次之;前端点火时火焰传播速率和面积均最小,产生了最小的内部压力峰值。前端点火时,容器内部压力出现了3个明显的压力峰值,中心和尾端点火时,只能观察到第1个和第3个压力峰值。并且,随着破膜压力的增加,中心和尾端点火时,火焰面积均增大,产生的内部压力峰值均增大。在前端点火的条件下出现了声学振荡的现象,对内部压力产生了显著的影响。