Joint Transmit Power Control and Rate Adaptation for Wireless LANs

Wireless local area networks (WLANs) are widely deployed recently. But many basic service sets (BSSs) nearby have to share a common channel due to the limitation in the spectrum resource. To get higher throughput with newly deployed access points (APs), it is necessary to improve spatial reuse of the channels by transmit power control (TPC). The achievable throughput, however, heavily depends on other factors such as rate adaptation (RA). Moreover, TPC without careful design may lead to asymmetric links and degrade fairness. In this paper, we jointly design TPC and RA to further improve total throughput of WLANs, and suggest (i) choosing power for each BSS by maximizing throughput which takes tradeoff between transmit rate and spatial reuse of channels, and, (ii) avoiding potential asymmetric links by explicit coordination among APs: each BSS uses almost the same power as its co-channel neighbors while BSSs far from each other may use different power levels as required. Extensive simulation evaluations confirm that the proposed scheme can greatly improve total throughput of dense WLANs, meanwhile fairness is retained.     

Theoretical Simulations of Electron-Induced Degradation of Perfluoropolyether

Electron-induced degradation of perfluoropolyether (PFPE) was simulated by a semi-empirical molecular orbital calculation of a model using a methylene oxide segment. The calculated heat of formation of the optimized structure showed that the anion radical was more stable than the neutral molecule by 186.9 kj/mol, while the cation radical had higher energy by 1281.7 kj/mol compared with the neutral. The calculated bond order indicated that several carbon-oxygen bonds were weakened in the anion radical. The estimated activation energies for the cleavage of the weakest C-O bond of the anion radical, the cation radical, and the neutral were 68.0, 22.1 and 334.2 kj/mol, respectively, and the ion radicals were expected to decompose easily. The anion intermediate formed after the above degradation of the anion radical was suggested to successively degrade to produce carbonyl fluoride.     

Study on the Effect of Elastic Stress and Microstructure of Low Carbon Steels on Barkhausen Noise

The present study investigates the effect of elastic stress and microstructure on Barkhausen noise in low carbon steels subjected to different heat treatments. Barkhausen noise in an as-received test piece and a test piece heated at 450 ^°C for 1.5 hours was found to increase with increasing elastic stress. However, in a test piece heated at 700 ^°C for 10 hours, Barkhausen noise was observed to saturate with increasing elastic stress following an initial increase. To clarify the reason for this saturation behavior, magnetization measurements were carried out and the microstructure and texture of the test pieces were evaluated using microscopy and electron backscatter diffraction. The results indicated that for the test piece heated at 700 ^°C for 10 hours, a drastic change in the microstructure occurred compared to that for the other test pieces. From the experimental and analytical results, it was concluded that for the former test piece, Barkhausen noise saturated under a low elastic stress due to the globularization of pearlite, which caused 90^° domain walls to become 180^° domain walls when a low elastic stress is applied.     

Long-term settlement behavior of soft grounds and secondary compression

Abstract

Settlement–time behaviors in the last stage of consolidation are studied both in the laboratory and in the field. It is shown that the long-term settlement–time curves observed in the field are linear with the logarithm of time and the rate of the long-term settlement are analogous to the rate of secondary compression measured in a laboratory. The finite difference consolidation analyses for cohesive soils exhibiting large amounts of secondary compression during primary consolidation provide fairly good predictions of the settlement–time curves observed in the laboratory and in the field. In this paper, the applicability of the secondary compression model established in the laboratory is examined in in situ conditions. The initial rate of secondary compression used in this paper has a predominant influence on the settlement–time curve with different drainage distances. It is emphasized that the assumption for unknown secondary compression behaviors during the primary consolidation has a predominant influence on the settlement–time curve.     

New Members of the Pb-based 1222 Superconductor Containing Phosphorus: (Pb0.75P0.25)Sr2(Ln1.9?x Ce x Sr0.1)Cu2O z (Ln=Sm and Gd)

We previously reported on the synthesis of new Pb-based 1222 superconductor containing phosphorus in the (Pb_0.75P_0.25)Sr₂(Eu_1.9−x Ce _x Sr_0.1)Cu₂O _z system. Recently, we have discovered new members of the Pb-based 1222 superconductor containing phosphorus in the (Pb_0.75P_0.25)Sr₂(Ln_1.9−x Ce _x Sr_0.1)Cu₂O _z (Ln=Sm and Gd) systems. In each system, it is found that the samples of almost the single 1222 phase can be obtained for a wide composition area of 0.3≤x≤1.0. After annealing under 143 atm O₂ atmosphere at 400 °C, each sample of Ln=Sm and Gd with x=0.3 is found to show an onset of resistivity-drop at about 28 K and at about 24 K, respectively. Moreover, each samples of Ln=Sm and Gd is found to show an onset of diamagnetic signal at about 25 K and about 22 K, respectively. From these facts, these samples of Ln=Sm and Gd are found to be new members of the Pb-based 1222 superconductor containing phosphorus.     

Internal state recovery of keystream generator LILI-128 based on a novel weakness of the employed Boolean function

This paper proposes an algorithm for internal state recovery of the keystream generator LILI-128 and introduces a novel approach for cryptanalysis of certain stream ciphers which belong to the class of nonlinear filters. The proposed cryptanalysis is based on a cryptographic feature/weakness of the Boolean function employed as the nonlinear filter. It is shown that the developed algorithm is significantly more efficient than the previously reported ones against LILI-128 and can recover the internal state with time complexities of pre-processing and processing of the order of 2⁴⁷ and 2³⁵, respectively, the space complexity of 2⁴⁷, and a sample of dimension approximately equal to 2⁴⁶. The developed cryptanalysis is also a practical confirmation on the significance of the so-called “non-normality” design criterion for Boolean functions.     

Immunostimulatory effects of water extract from bulbus arteriosus in tuna in vitro

Immunostimulating effects of water extract from bulbus arteriosus in tuna were examined and found to enhance IgM production by human hybridoma HB4C5 cells. When tuna bulbus arteriosus extract was heated, the IgM production-stimulating activity was decreased or lost. To identify the active substance, the extract was partially purified by anion-exchange chromatography, and proteins contained in positive fractions were analyzed by LC-MS/MS. The positive fractions contained lactate dehydrogenase, triosephosphate isomerase, enolase, and haemoglobin. Each of these four proteins was verified to enhance IgM production by HB4C5 cells with the commercially available purified proteins, suggesting that all of these four proteins are active substances in the extract. The immunostimulatory effect of these proteins was also examined on mouse primary spleen lymphocytes in vitro. Lactate dehydrogenase enhanced IgA, IgG, and IgM production and triosephosphate isomerase enhanced IgA and IgG production. In particular, lactate dehydrogenase had the strongest Ig production-stimulating effect on HB4C5 cells and on mouse primary lymphocytes. Thus, fish viscera may serve as an important raw material for the enhancement of the acquired immune system, once processed.     

Heat transfer characteristics in a condenser of closed two‐phase thermosyphon: Effect of entrainment on heat transfer deterioration

Condensation heat transfer in a closed two‐phase thermosyphon is experimentally examined using two different types of test section. Test Section 1 is a straight‐pipe‐type thermosyphon, whereas Test Section 2 has a large‐diameter evaporator compared with a condenser to minimize entrainment at the evaporator. Condensation heat transfer in Test Section 1 shows much lower heat transfer coefficients than those estimated by a Nusselt theory. This low condensation heat transfer occurs due to a working fluid entrainment. It is confirmed from a result of Test Section 2 that the condensation heat transfer is similar to the values predicted by the Nusselt theory as far as the effect of the working fluid entrainment is negligible and flooding does not occur. A new correlation for the heat transfer coefficient considering the effect of entrainment is proposed. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(3): 212–225, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10030     

Diploid porcine parthenotes produced by inhibition of first polar body extrusion during in vitro maturation of follicular oocytes

We investigated nuclear progression and in vitro embryonic development after parthenogenetic activation of porcine oocytes exposed to cytochalasin B (CB) during in vitro maturation (IVM). Nuclear progression was similar in control oocytes and oocytes matured in the presence of 1 microg/ml CB (IVM-CB group) by 37 h IVM; at this time the proportion of oocytes that had reached or passed through the anaphase-I stage did not differ significantly between the IVM-CB and the control groups (61.3 and 69.9% respectively; P < 0.05). After IVM for 37 h, no polar body extrusion was observed in the IVM-CB group. In these oocytes, the two lumps of homologous chromosomes remained in the ooplasm after their segregation and turned into two irregular sets of condensed chromosomes. By 41 h IVM, the double sets of chromosomes had reunited in 89.5% IVM-CB oocytes and formed a single large metaphase plate, whereas 68.8% of the control oocytes had reached the metaphase-II stage by this time. When IVM-CB oocytes cultured for 46 h were stimulated with an electrical pulse and subsequently cultured for 8 h without CB, 39.0% of them extruded a polar body and 82.9% of them had a female pronucleus. Chromosome analysis revealed that the majority of oocytes that extruded a polar body were diploid in both the control and the IVM-CB groups. However, the incidence of polyploidy in the IVM-CB group was higher than that in the control group (P < 0.05). In vitro development of diploid parthenotes in the control and the IVM-CB groups was similar in terms of blastocyst formation rates (45.8 and 42.8% respectively), number of blastomeres (39.9 and 44.4 respectively), the percentage of dead cells (4.3 and 2.9% respectively), and the frequency of apoptotic cells (7.3 and 6.3% respectively). Tetraploid embryos had a lower blastocyst formation rate (25.5%) and number of cells (26.2); however, the proportion of apoptotic nuclei (7.0%) was similar to that in diploid parthenotes. These results suggest that the proportion of homozygous and heterozygous genes does not affect in vitro embryo development to the blastocyst stage.