A new practical parallel garbage collection algorithm and its correctness proof are presented. Some results of its implementation applied to a small size LISP system are reported. The algorithm, which is constructed on the condition that all active lists are bound in the linear stack, needs only one mark bit for each node and a scan-request-flag (SREQ) for the system. The minimum utilization of critical sections, where the operations on SREQ are performed, dispenses with the need for multicolored marking, such as white, gray or black. Also marking efficiency improves since it enables applying a recursive trace-and-mark method instead of a simple scan-and-markmethod. An outline of the correctness proof is as follows : It is proned by induction that the relation, wherein the active-node-set is a subset of the mark-reachable-set, which is defined as the set of all the nodes to which some links exist from any nodes already marked, is retained during the mark propagating phase for any list processing primitives, so that the algorithm guarantees that no active nodes are reclaimed. Last, the implementation of a small size LISP system with this algorithm is reported. The comparison between the parallel system and the regular one is discussed on the basis of actual data.

The problem of concurrent access to an index structure is that of allowing a maximum number of processes to operate without impairing the correctness of their operations. Recently, Bayer et al. (1977) presented some simple locking protocols to the problem of concurrent access to indexes which are implemented B^*-trees. In this paper, we give a new locking protocol that achieves higher concurrency than that of Bayer et al., by minimizing the area on which the exclusive locks are placed. We also show that this solution is deadlock free.

Average intensity of far-field radiation patterns of laser light emitting from an end face of the multimode optical fiber is theoretically analyzed by assuming a Gaussian autocorrelation function for the refractive-index inhomogeneities in an optical fiber. The average intensity distribution of far-field patterns is characterized by both the statistical scale of index fluctuations and the fiber parameters of core radius and refractive-index profile. It is shown that the on-axis maximum intensity decreases as the correlation length of refractive-index inhomogeneities becomes small compared with the wavelength of light, whereas the off-axis average intensity decays gradually with the increase of the distance from the axis. The average intensity distributions obtained here are found to be nearly Gaussian for both types of the optical fiber with step-index and graded-index profiles of the refractive index.

Dynamic properties of electrical circuits containing a Josephson junction are studied analytically by approximating the sinusoidal current-phase relation by a triangular one. Analytical expressions are obtained for the circuit-parameter dependences of transient voltage waveforms, ac ripples of stationary-state voltage oscillation and minimum currents in several typical circuits, which are shown to be in good agreement with numerical results. It is also shown that these quantities can be well characterized in simple forms in terms of a frequency peculiar to each circuit.

Some practically optimal conditions for coexistence of analog and digital systems in an intersystem interference environment may be found in a compromise between both systems. To find them, as a first step we have investigated and discussed the effects of multiple wideband FM systems upon an M-ary coherent PSK system under the assumption that both systems are sharing the same radio frequency bands. For that, in this paper we propose an analysis method which is directly applicable to the wideband FM interferers. The symbol error performance of MCPSK system in the presence of Gaussian noise and cochannel or adjacent channel interference from wideband FM systems is evaluated and given in graphes as functions of CNR, CIR and normalized carrier separation. From the results obtained here, one can expect some optimal or suitable operating conditions (frequency allocation, bandwidth and power) for a PSK channel in the intersystem interference from analog FM channels.

Simple formula has been proposed to estimate baseband bandwidth of an optical transmission line made of different fibers spliced together. Using the formula, cumulative bandwidth is predicted merely from the bandwidth for each individual fiber. The usefulness of the formula has been confirmed by experiments.

Heat transfer mechanism for the compatible repeater housing, used for coaxial transmission systems, is studied. Temperature rise for the repeater housing and repeater surface is calculated in detail. An efficient improvement plan for the thermal characteristics of the new repeater housing is suggested and confirmed by the experiment.

Optimum inspection schedule is discussed to maximize the availability for a two-unit parallel redundant system when a failure of unit is detected only by actual inspection. The stationary availability is derived by applying Piecewise Markov Process under the assumption that a failure distribution is exponential and other distributions are arbitrary.