A future satellite communications system using millimetre-wave bands and an on-board processor

This paper proposes the system concept of a personal satellite communications system that will be available in the first decade of the 21st century. Technologies of millimetre-wave bands and an onboard processor with baseband switching promise to meet the requirements of a personal communications system: portability, low-cost, and large capacity. Based on the prospects of these technologies, the most likely parameters for the future personal satellite communications system and the configuration of a suitable on-board processor are proposed. A trial model of such an on-board processor has been made. In this paper, details of the trial model on-board processor and its future developments are described.     

Nucleophilic vinyl polymerization of 2-alkenyl-2-oxazolines activated by trimethylsilyl trifluoromethanesulfonate

Summary The present paper describes a novel nucleophilic vinyl polymerization of 2-alkenyl-2-oxazolines catalyzed by trimethylsilyl trifluoromethanesulfonate (TMSOTf) via an activated monomer mechanism. When 2-isopropenyl-2-oxazoline (IPO) was treated with 5 mol % of TMSOTf at 40°C, a vinyl propagated polymer was obtained almost quantitatively. The yield of the polymer increased as the increase of the concentration of TMSOTf, while the molecular weight of poly(IPO) was independent of it. 4,4-Dimethyl-2-vinyl-2-oxazoline and 2-isopropenyl-4,4-dimethyl-2-oxazoline also produced vinyl propagated polymers in the presence of TMSOTf, whereas 2-vinyl-2-oxazoline gave an insoluble gel even at-78°C.     

Fracture toughness and fatigue crack propagation in high strength steel from room temperature to −180°c

Fracture toughness under tensile test and fatigue test on high strength steel at temperature ranging from room temperature to ?180°C were experimentally studied. The value of fracture toughness under fatigue test is considerably tower than that obtained under tensile test.Within the range from room temperature to ?100°C the following results were obtained: the power coefficient δ of the fatigue crack propagation rate $\text{[(dc)/(dN)] = AΔK}{}^5$ is related with [(1)/($\text{T}$)] as: $\text{δ = b}{}_1\text{+ [(a}{}_1\text{)/(kT)]}$. $\text{[(dc)/(dN)]}$ shows Arrhenius type, and, however, different equation from usual stress dependent rate process equation. The trend is in good agreement with the dislocation dynamics theory of fatigue crack propagation.     

Task-oriented force control of parallel link robot for the assembly of segments of a shield tunnel excavation system

This paper proposes a task-oriented force control system for the assembly of segments of a shield tunnel excavation system. First, we design a generalized coordinate system referred to as a task-oriented coordinate system, so that the position and orientation of a segment can be adjusted compliantly according to the external force from existing segments with which the segment is assembled together. Then, a hybrid position/force control algorithm is designed for a parallel link robot with hydraulic actuators. The system is experimentally applied to the assembly of honey-comb shaped segments. The experimental results illustrate the validity of the proposed system.     

Cationic ring-opening polymerization of spirophosphorane, 5-phenyl-1,4,6,9-tetraoxa-5-phosphaspiro[4,4]nonane

Summary This paper reports new cationic ring-opening polymerization of a spirophosphorane, 5-phenyl-1, 4, 6, 9-tetraoxa-5-phosphaspiro (4, 4) nonane, 1. The polymerization of 1. was induced by cationic initiators such as methyl trifluoromethanesulfonate (MeOTf), BF₃·OEt₂, and Et₃O⁺-BF₄ ^– to give polymer 2 consisting of two different units, 2a and 2b. During the reaction cyclic phosphonate 3 and 1,4-dioxane were simultaneously produced. The formation of unit 2b is considered to be due mainly to the cationic ring-opening polymerization of 3.