Unidirectional Loop Research Articles

Simple Optical Pulse Lengthening Setup for the Subnanosecond Range

An easily realizable, passive pulse lengthening method is suggested to increase the pulse duration of light pulses originally of 100 psec-1 nsec length. The method applies an unidirectional light loop based on total internal reflections and polarization selectivity of the glass/air interface.

Further studies on interactions between periaqueductal gray, nucleus accumbens and habenula in antinociception

Previous findings from this laboratory with the intracerebral microinjection technique suggested that the periaqueductal gray (PAG), nucleus accumbens, and habenula might constitute a unidirectional loop to play their roles in pain modulation. In the present study we demonstrate that intra-habenular injection of naloxone antagonizes the analgesia elicited by morphine injected into the periaqueductal gray (PAG) and that intra-accumbens injection of naloxone is capable of attenuating the analgesic effects of morphine injected into the habenula. These results indicate that the relationships between these nuclei may be more complex than the putative unidirectional loop.

Unidirectional Loop Network Layout Problem in Automated Manufacturing Systems

In this paper, we address the design of unidirectional loop network layouts for automated manufacturing environments. We show that the problem is NP-complete. Using a workstation interchange argument, we develop dominance relationships for easy identification of local optimal solutions. Our results suggest the need for simple heuristics to solve the problem. We identify cases in which the heuristics perform optimally, and we analyze the worst case behavior of the heuristics. We develop an optimal branch-and-bound procedure that is computationally efficient for medium-sized problems. We also present a decomposition principle helpful for dealing with large workflow matrices. We report computational results on the heuristics and the branch-and-bound procedure. We show that one of the heuristics performs impressively well in terms of solution quality and computational time requirements.

Naloxone blocks opioid peptide release in periaqueductal gray and amygdala elicited by morphine injected into N. accumbens

Previous studies from this laboratory suggested that the periaqueductal gray (PAG), nucleus accumbens, and amygdala might take part in a serial, unidirectional mesolimbic loop to play their roles in pain modulation. It has been proposed that morphine injected into one of these nuclei would cause the release of opioid peptides in one nucleus after another. This working hypothesis was examined in the present study by perfusing simultaneously the PAG and the amygdala after microinjection of morphine into the N. accumbens. It was found that microinjection of morphine increased the content of immunoreactive enkephalins (ir-ENK) and immunoreactive β-endorphin (ir-β-EP) in the perfusate of the PAG and the amygdala. When the perfusion fluid contained 3 μM of naloxone, the increase of ir-ENK and ir-β-EP was reduced significantly. These results indicate that the three nuclei were not serially connected in a unidirectional loop.

A graph-theoretic heuristic for designing loop-layout manufacturing systems

In flexible manufacturing systems, the type of materials handling system strongly influence the machine layout. For layouts where the machines are arranged in a loop and the material handling system is uni-directional, a measure of congestion for a part is the number of times the part traverses the loop before its processing is completed. This paper investigates the problem of determining a machine layout for uni-directional loop networks which minimizes the maximum number of loop traversals for a family of parts. Based on graph-theoretic arguments, a heuristic is developed which constructs a layout from a solution to the linear-programming relaxation of the problem. Preliminary computational results are also presented.

Broadband tunable single frequency diode-pumped erbium doped fibre laser

A single frequency erbium fibre laser with continuous wavelength tuning over the range 1525–1568 nm has been demonstrated using a unidirectional loop mirror (ULM) configuration. The fibre laser is diode pumped at 1480 nm with a threshold of 9mW, slope efficiency of 12% and has a linewidth of less than 295 kHz.

Naloxone blocks the release of opioid peptides in periaqueductal gray and N. accumbens induced by intra-amygdaloid injection of morphine

The working hypothesis that the periaqueductal gray (PAG), N. accumbens and amygdala were connected serially in a unidirectional loop for antinociception, in which Met-enkephalin and β-endorphin were considered to be two important analgesic neurotransmitters, was examined by simultaneously perfusing the PAG and N. accumbens after microinjection of morphine into the amygdala. Intra-amygdaloid injection of morphine increased the release of enkephalins and β-endorphin in the PAG and N. accumbens. When the perfusion fluid contained 3 μM of naloxone, the release of enkephalins and β-endorphin was reduced in both the PAG and the N. accumbens. These results do not support the hypothesis of a unidirectional loop and its putative sequence.

A deadlock-free communication kernel for loop architecture

We discuss a deadlock-free communication structure for an unidirectional loop of an arbitrary number of message-passing computers.

Mean delay in synchronous packet networks with priority queueing disciplines

A Markov model which approximates the behavior of networks that transport messages of varying priority classes is developed. The model is shown to accurately predict behavior for a tandem network with departures and an unidirectional loop network. In the cases which required approximation, the model was validated by performing extensive computer simulation and comparing it with analytical results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

On the path layout and operation of an AGV system serving an FMS

A major step in the design of an AGV system involves the choice of its layout. Three different AGV layouts serving the same FMS are compared in this paper: a bidirectional line, a bidirectional loop and a unidirectional loop. Different numbers of vehicles are tried by running an ECSL program written for the AGV/FMS simulation. Various velocities and scheduling policies are used which show that bidirectional layouts are more advantageous than unidirectional ones in general, although the latter have been rendered more competitive by the application of a control algorithm for the avoidance of blockages on the track. Scheduling policies, however, are proved to be a key issue. It is therefore necessary to refer any comparison of layouts to a particular scheduling policy. In addition, it was observed that a compromise between factors measuring AGV-layout performance has to be made when assessing layouts, since these factors often follow opposite trends.

Some Studies on Delayed Feedback Circuits

This paper attempts to describe a new method by which periodic signals in noise can be detected easily without the aid of an expensive correlator. In principle, the circuit consists of a delay network which is inserted as a part of a unidirectional loop connected with the main circuit through a hybrid coil. The delay time must be equal to, or an integral multiple of, the signal period to be detected. The delay time also must be longer than the inverse figure of the preceding network bandwidth. Successive noises will be superimposed one after another at random in circulation, while the signals are superimposed in phase. This means an improvement in the signal-to-noise ratio. Theoretically, the ideal basic delayed feedback circuit gives an improvement in the snr of 7.66 db, and in the apparent Q of 9.06. Further improvement can be expected by the use of active circuits. Possible applications are for producing artificial reverberation, a narrow-band filter, and a short-time memory circuit. The response of the delayed feedback circuit is like a comb filter. The circuit also can extract complicated periodic waves without an appreciable distortion.

Synthesis of Transfer Functions by Active RC Networks

The paper considers the synthesis of arbitrary passive transfer functions using stable active RC networks. The work undertaken is oriented toward discussing general methods of synthesis rather than specific design procedures. The structures used consist of single unidirectional feedback loops. These methods, although by no means providing the most general procedure for the synthesis of active networks, appear to offer a logical step toward this aim.