Flux linkage areas of coupling current loops for different shape cable-in-conduit conductor

For large scale application such as fusion magnets, the cable-in-conduit conductor (CICC) is the most promising conductor because of its high mechanical strength under large electromagnetic force. However, there are still remained issues about degradation of critical current of Nb₃Sn conductor and unpredictable AC loss. With regard to the second item, inter-strand coupling current loss is dominant among the AC losses and unpredictable before fabricating large scale conductor. The strand displacements which are caused by the compaction of the conductor in order to increase its current density would cause the loss. In order to do quantitative investigation of the relation between the loss and the strand displacements, we measured strand traces for circular conductor and rectangular conductor. The evaluation of the flux linkage areas which are driving forces of the coupling current indicated that the flux linkage areas have strong dependence on the changing magnetic field only for the rectangular one. It also indicated that the loss should be large when the field is applied from the direction which is perpendicular to the wide surface of the conduit.     

Study on mechanism of strength distribution development in vacuum-dewatered concrete based on the consolidation theory

The strength and hardness of a concrete slab surface are considered to be significantly affected by concrete bleeding. Vacuum dewatering is reported to be quite effective in imparting high density and strength. However, in Japan, in contrast with concrete work in civil engineering applications, concrete work in the field of building construction has not been successfully treated by this method. In an earlier report, the authors pointed out the strong relationship between strength distribution and density distribution in vacuum-dewatered concrete, both of which gradually decrease from the top surface to a depth of about 15 cm. The main purpose of the present study is to discuss the mechanism of the occurrence of such distribution of strength and density, based on consolidation theory. In an experiment, pore water pressure distribution in concrete is measured by means of an original measuring system. The results of the experiment confirm that the consolidation theory is quite effective in explaining the internal properties of vacuum-dewatered concrete as well as those of press-dewatered concrete. A prediction method for the strength improvement of concrete by vacuum dewatering is also discussed. It was considered likely that pore water pressure distribution generated by vacuum dewatering could be attributable to the influences of capillary tension and viscous resistance. This mechanism was verified by model experiment.     

简单自适应控制在水压伺服缸系统中的应用

In this research, the positioning control of water hydraulic servo cylinder system with the simple adaptive control (SAC) is discussed. Conventional model reference adaptive control (MRAC) also achieves good tracking performance for cylinder control, but the controller structure was much complicated and was not easy to be realized in application. Compared with MRAC, SAC has simpler and lower order structure, i.e., has higher feasibility. But only few papers concerning with the application of the control performance of SAC to hydraulics and pneumatics are available, especially for water hydraulics. In this paper, we will examine and evaluate the control performance of the SAC strategy and it is confirmed that SAC gives better tracking performance compared with PI control.     

Formation of ultra-fine amorphous powders in Fe-M-B (M = transition metal) systems by chemical reduction method and their thermal and magnetic properties

Amorphous ultra-fine powders in (Fe or Co)-B and Fe-M-B (M = Cr, Mn, Co, or Ni) systems were produced by reduction of metal ions in an aqueous solution by use of KBH₄. The powders have a spherical shape with diameters ranging from 5 to 20 nm. The boron concentration is in the range of 24.1 to 44.1 at. pct and the composition of metal elements can be controlled by changing the concentration of metal ions. Crystallization temperatures and heats of crystallization for the Fe-Ni-B powders agree with those obtained for the amorphous alloys of the same composition produced by melt spinning. Furthermore, the compositional dependences of the crystallization temperature, coercivity, and magnetization measured in the field of 2 kOe are very similar to those obtained in the chemically synthesized (Fe-Co)₆₃B₃₇ amorphous powders and melt-spun (Fe-Co)₇₈Si₁₀B₁₂ or (Fe-Co)₇₅Si₁₅B₁₀ amorphous ribbons. It is concluded that there is no significant difference in the amorphous structure obtained in chemically synthesized powders and the melt-spun ribbons, in spite of an essential difference in the formation mechanism of these amorphous alloys. JUNJI SAIDA, on leave from Hanshin Research and Development Laboratories, Nisshin Steel Com-pany Ltd., Sakai 592, Japan     

Induction of ST-segment elevation by regional myocardial stretch in normal canine hearts in vivo

The purpose of this study was to evaluate ST-segment elevation induced by regional myocardial stretch without myocardial ischemia in canine hearts. A strain gauge arch (TH-601T) was sutured to the left ventricular epicardium, parallel to the short axis, to shorten the end-diastolic length of the myocardium beneath the arch (stretch zone; SZ) and to produce regional myocardial stretch in each of 6 dogs. An increase in preload caused by altering the height of a saline-filled reservoir affected prolongation or shortening of the myocardium both in the SZ and outside the arch (normal zone; NZ) to increase myocardial stretch. An epicardial electrocardiogram was recorded in both the SZ and the NZ. After suture of the strain gauge arch, the ST segment was elevated in the SZ. An increase in preload augmented stretch during systole in the SZ, resulting in additional ST-segment elevation. These results suggest that regional myocardial stretch itself plays an important role in ST-segment elevation.     

New oxide superconductors in the Sr-Bi-Cu-O system

New oxide superconductors in the Sr-Bi-Cu-O system were prepared by the conventional processing techniques consisting of mixing, pressing and sintering. The compositions of the superconductors are located in a range surrounded by CuO, SrCu₂O₃ and Sr_0.9Bi_1.1O_2.55. No distinct compositional change in the critical temperature,T _c, is observed and the value is 8 to 9 K at onset and 4 to 5 K at zero resistance. The zero resistance value increases on replacement of strontium by sodium or potassium which have different atomic valences and a nearly equal ionic radii compared to strontium, accompanied by an increase in the positive slope of electrical resistance and reaches a maximum value of 6.7 K for Sr_0.9Na_0.1 Bi₁Cu₂O_4.45 and 5.9 K for Sr_0.9K_0.1Bi₁Cu₂O_4.45. The further increase in sodium and potassium content brings about the disappearance of superconductivity, along with an extreme increase in the negative slope of electrical resistance. The increase inT _c for the Sr-Bi-Cu oxides with the replacement by sodium or potassium is probably because the replacement gives rise to a change in the valence of copper atoms and/or the formation of an oxygen-deficient structure.     

Preparation and properties of nickel silicide layers by the diffusion and CVD processes using Si2Cl6 as a source of silicon

Nickel plate was siliconized with a gas mixture of Si₂Cl₆, H₂ and argon in the temperature range 400 to 900° C, and the siliconizing conditions and some of its properties were examined, Appreciable weight increase of the nickel plate was observed above 450° C, which is 200 to 300° C lower than that obtained using SiCl₄ as a source of silicon. Siliconizing of the surface and the resistance to high-temperature oxidation and hot corrosion were improved, Nickel silicide layers were also obtained by the CVD process using a gas mixture of Si₂Cl₆, H₂ and argon.