Static Frequency Assignment in Cellular Networks

A cellular network is generally modeled as a subgraph of the triangular lattice. In the static frequency assignment problem, each vertex of the graph is a base station in the network, and has associated with it an integer weight that represents the number of calls that must be served at the vertex by assigning distinct frequencies per call. The edges of the graph model interference constraints for frequencies assigned to neighboring stations. The static frequency assignment problem can be abstracted as a graph multicoloring problem. We describe an efficient algorithm to multicolor optimally any weighted even or odd length cycle representing a cellular network. This result is further extended to any outerplanar graph. For the problem of multicoloring an arbitrary connected subgraph of the triangular lattice, we demonstrate an approximation algorithm which guarantees that no more than 4/3 times the minimum number of required colors are used. Further, we show that this algorithm can be implemented in a distributed manner, where each station needs to have knowledge only of the weights at a small neighborhood. Received May 13, 1997; revised August 24, 1998.     

The influence of intrathecal fentanyl on the characteristics of subarachnoid block for caesarean section

Forty healthy parturients scheduled for elective Caesarean section were randomly allocated to receive either 0.3 ml 0.9% saline (control group, n = 20), or 15 micrograms (0.3 ml) fentanyl (treatment group, n = 20) added to 2.5 ml 0.5% hyperbaric bupivacaine given intrathecally in the sitting position. A sensory block to T4 was achieved after 6.5 min in those who received fentanyl compared to 8.0 min in the control group; this was not significantly different. The highest level of sensory block achieved in both groups was similar. Ephedrine was required earlier (p < 0.05) in those who received fentanyl but the total requirement of ephedrine intra-operatively was similar. Fentanyl significantly improved the quality of intra-operative surgical anaesthesia as none of the patients in the treatment group complained of discomfort compared with seven in the control group (p < 0.05). Similarly those in the treatment group had better comfort scores as evaluated by visual analogue score (p < 0.01). Regression of anaesthesia to T12 took longer (184 vs 156 min, p < 0.05) in those who received fentanyl but this did not affect the total requirement of morphine in the first 24 h after operation. There was no difference in the incidence of side effects in the mother and no adverse effects were detected in the baby. The results indicate that adding 15 micrograms fentanyl to hyperbaric bupivacaine for spinal anaesthesia markedly improves intra-operative anaesthesia for Caesarean section.     

Modulation of serratiopeptidase transdermal patch by lipid-based transfersomes

Serratiopeptidase is a proteolytic enzyme obtained from serratia marcescens strain E-15 and used as anti-inflammatory and analgesic drug. Serratiopeptidase undergoes first pass metabolism, causes the gastrointestinal disturbance and systemic toxicity after oral administration. To overcome the limitations of serratiopeptidase, transdermal drug delivery system is an alternative method. So, the aim of present work was to modulate serratiopeptidase transdermal patch by lipid-based transfersomes. Particle size of drug was the major concern to cross stratum corneum which acts as a barrier. This difficulty was surmounted by modulating the vesicles such as transfersomes which carries the drug into the skin by passing the barrier of stratum corneum. Serratiopeptidase was encapsulated in transfersomes in different ratios of lecithin and cholesterol. Particle size of transfersomes, folding endurance, thickness, tensile strength, adhesion test, encapsulation efficiency, in vitro and in vivo release, Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimeter (DSC) studies of patch were used as characterization parameters. Serratiopeptidase transfersomes size was found to be 50 µm with smooth surface. The promising entrapment efficiencies of transfersomes and formulation were found to be 96.76 and 98.7%, respectively. In vitro and in vivo release studies showed controlled and steady release of serratiopeptidase for 24 h. FTIR and DSC confirmed the encapsulation of drug in patch without interaction. It is concluded that transfersomes are interesting carriers for enzymatic drugs for topical application.     

Antioxidant potential of herbs and spices during deep frying of ghee

The present study was carried out to evaluate antioxidant potential of ashwagandha, clove, coriander, green tea, shatavari and vidarikand extracts as compared to BHA. Clove, coriander and green tea extracts showed significantly higher antioxidant activity than vidarikand, shatavari and ashwagandha extracts. Radical‐scavenging activity by DPPH model system revealed that clove and green tea extracts were superior to other extracts. All the natural antioxidants significantly reduced the formation of peroxides, FFA, thiobarbituric acid value and conjugated dienes. Ghee with added clove, green tea and coriander extracts showed higher induction period as compared to ghee containing vidarikand, ashwagandha, shatavari or BHA.     

卷取温度对Q960热轧薄钢板组织与性能的影响

研究了中低温卷取温度对Q960热轧薄板钢显微组织和力学性能的影响。结果表明,随着卷取温度从562℃降至359℃,Q960热轧板的显微组织由粒状贝氏体+少量的珠光体转变为下贝氏体;渗碳体含量明显增加而MC相略有下降。低温或超低温卷取可以减轻或消除Q960热轧板的带状组织。采用非再结晶轧制和约350℃低温卷取可以使Q960热轧卷板获得1000 MPa以上的非比例延伸强度,同时冲击性能良好。     

Performance Analysis Integration in the Uintah Software Development Cycle

The increasing complexity of high-performance computing environments and programming methodologies presents challenges for empirical performance evaluation. Evolving parallel and distributed systems require performance technology that can be flexibly configured to observe different events and associated performance data of interest. It must also be possible to integrate performance evaluation techniques with the programming paradigms and software engineering methods. This is particularly important for tracking performance on parallel software projects involving many code teams over many stages of development. This paper describes the integration of the TAU and XPARE tools in the Uintah Computational Framework (UCF). Discussed is the use of performance mapping techniques to associate low-level performance data to higher levels of abstraction in UCF and the use of performance regression testing to provide a historical portfolio of the evolution of application performance. A scalability study shows the benefits of integrating performance technology in building large-scale parallel applications.     

振荡热管的热阻变化规律及烧干特性

振荡热管作为高效传热元件,在解决微小空间而热通量较高的元器件散热方面具有独特的优势。虽然振荡热管结构简单,但其内部运行规律多变复杂,目前还处于探索研究阶段。通过对实验结果的分析,得到随加热功率和充液率改变振荡热管的热阻变化规律,探讨了不同工况所对应的传热机理;同时还对振荡热管的烧干特性进行了分析和研究。所做工作为建立振荡热管理论模型、认识其传热规律提供参考。     

Effect of aluminum nanoparticles on rheological behavior of HTPB-based composite rocket propellant

The aim of this article was to understand the rheology of composite propellant containing aluminum nanoparticles, as it is a highly filled mixture of solids and is difficult to process. Aluminum nanoparticles utilized as a filler were characterized using X-ray diffraction spectroscopy, scanning and transmission electron microscopy. It was confirmed that the material was pure aluminum, spherical in shape and nano-sized (96.8 nm). The effects of shear stress, shear rate, strain, aluminum nanoparticles concentration, and shear time on rheology were investigated thoroughly, which confirmed a non-Newtonian, time-dependent, shear-thinning, and viscoplastic flow behavior. The composition which had 0% nanoparticles showed the lowest thixotropy index of 50.86 Pa/s, and the difference was almost minimal for compositions containing 0% and 6% nanoparticles. The propellant containing 6% nanoparticles did not yield, as compared to the compositions. The results indicate that nanoparticles have a considerable effect on the rheology of the composite propellant.     

羟基酪醇的研究进展

羟基酪醇是一种天然多酚类化合物,具有多种生物和药理活性,主要存在于橄榄油和加工橄榄油产生的废水中。本文主要综述了羟基酪醇的主要药理活性,包括抗癌、抗菌、抗炎作用,介绍了羟基酪醇的从生产橄榄油的废渣、废水中的提取、分离方法,化学合成方法以及生物合成方法。