Recently, researchers in various fields have shown interest in the behavior of creatures from the viewpoint of adaptiveness and flexibility. Ants, known as social insects, exhibit collective behavior in performing tasks that can not be carried out by an individual ant. In ant colonies, chemical substances, called pheromones, are used as a way to communicate important information on global behavior. For example, ants looking for food lay the way back to their nest with a specific type of pheromone. Other ants can follow the pheromone trail and find their way to baits efficiently. In 1991, Colorni et al. proposed the ant algorithm for Traveling Salesman Problems (TSPs) by using the analogy of such foraging behavior and pheromone communication. In the ant algorithm, there is a colony consisting of many simple ant agents that continuously visit TSP cities with opinions to prefer subtours connecting near cities and they lay strong pheromones. The ants completing their tours lay pheromones of various intensities with passed subtours according to distances. Namely, subtours in TSP tourns that have the possibility of being better tend to have strong pheromones, so the ant agents specify good regions in the search space by using this positive feedback mechanism. In this paper, we propose a multiple ant colonies algorithm that has been extended from the ant algorithm. This algorithm has several ant colonies for solving a TSP, while the original has only a single ant colony. Moreover, two kinds of pheromone effects, positive and negative pheromone effects, are introduced as the colony-level interactions. As a result of colony-level interactions, the colonies can exchange good schemata for solving a problem and can maintain their own variation in the search process. The proposed algorithm shows better performance than the original algorithm with almost the same agent strategy used in both algorithms except for the introduction of colony-level interactions.

In this paper, we propose a new cooperative search algorithm based on pheromone communication for solving the Vehicle Routing Problems. In this algorithm, multi-agents can partition the problem cooperatively and search partial solutions independently using pheromone communication, which mimics the communication method of real ants. Through some computer experiments the cooperative search of multi-agents is confirmed.

This paper presents a new type of optical probe designed to detect magnetic near-fields with high accuracy in the gigahertz range. Its probe head consists of a loop antenna element doubly loaded with LiNbO3 electro-optic crystals. Through an optical technique, it can work as a conventional double-loaded loop probe without metallic cables or an electrical hybrid junction. We examined probe characteristics for magnetic field detection up to 20 GHz. We confirmed that the probe can measure magnetic fields near a microstrip line in the gigahertz range and can suppress influence of electric fields.

An optically scanning electromagnetic field probe system consisting of an electro-optic or magneto-optic crystal and a galvano scanner is proposed for high-speed electromagnetic field distribution measurements. We used this technique to measure electromagnetic field distributions near printed circuit boards or ICs to address electromagnetic compatibility problems or in designing electronic devices. With our scanning system, we can measure the electric field intensities of about 40,000 points with an area of 4040 mm in about 3 minutes (4 ms per point) up to 2.7 GHz. We measured the electric near-field distribution above a five-split transmission line using a cadmium telluride (CdTe) electro-optic crystal. The measurement results showed that the spatial resolution of the system was less than 400 µm in the case of a common current with a crystal thickness of 1 mm. The electric near-field distribution above a microstrip line filter was measured using LiNbO3 electro-optic crystal. Changes in the distribution according to the frequency were observed. The experimental results obtained using this system were compared with simulation results obtained using a finite-difference time-domain method. The overall results indicated that the measurement system is capable of accurately measuring electric near-fields. We also discuss the invasiveness of the measurement system, due to the electro-optic crystals, in terms of both the experimental and simulated results.

Agent-based simulations are expected to enable analysis of complex social phenomena. In such simulations, one of the important behaviors of the agents is negotiation. Throughout the negotiations, the agents can make complex interactions with each other. Therefore, the ability of agents to perform negotiation is important in simulations of artificial societies. In this paper, we focus on price negotiations, in which the two sides have opposing interests. In the conventional price negotiation model, the process consists of an alternate succession of directly presented offers and counter-offers exchanging the desired prices. As an extended price negotiation model, we introduce virtual words to mimic the negotiation techniques of humans for indirectly presenting the desired price. The process of the proposed negotiation model consists of an alternate succession of offers of desired price and counter-offers of a word. The words represent the degree of the agent's demand. We propose agents with reinforcement learning who can acquire the ability to distinguish words and use them to negotiate. As a result, we will show that the virtual words became meaningful in the process of negotiations between agents whose negotiating strategies are acquired by reinforcement leaning.

Ultrashallow p-type layers have been formed using an one-wafer type reactor for rapid vapor-phase doping (RVD) with lamp annealing system. Bipolar and MOS transistors were fabricated using the system for the first time. The process includes the injection of the B2H6 diffusion source gas with hydrogen carrier gas at room temperature and rapid thermal annealing using lamps. Ultrashallow boron doping was achieved at 900 for 60 seconds; that is, the junction depths were less the 60 nm with a peak boron concentration of between 1019 and 1020 cm-3. The sheet boron concentrations is controlled by adjusting the flow rate of B2H6. To show the potential of the process, bipolar and MOS transistors were fabricated. The base regions of conventional bipolar transistors were formed by rapid vapor-phase doping. Transistors with 20-nm base and emitter were fabricated and they showed current gain of 150. Shallow source and drain of PMOS transistors were also formed. The threshold voltage roll-off was suppressed down to gate length of 0.22 µm, while devices with BF2-implanted source and drain showed the roll-off below 0.5 µm. Devices with RVD-source and drain thus have drain current 1.5 times higher than those with BF2 ion implantation. RVD provides both good short-channel characteristics and high current drivability.

Electromagnetic field probes inevitably disturb the original distribution of the field when they are positioned close to a device. This disturbance in turn affects measurement accuracy and device operation. We developed an optical magnetic field probe, comprising a loop antenna element and an electro-optic crystal, for highly accurate magnetic near-field measurement in the GHz frequency range. We analyzed the invasiveness of the optical magnetic field probe quantitatively both experimentally and using finite difference time domain simulation. We found that eliminating the metal cable reduced the disturbance of the surrounding field that was to be measured. In addition, we investigated the magnetic field detection characteristics of the probe and its influence on the operation of a microstrip line. The optical magnetic field probe was less invasive and provided more accurate measurement.

The superconducting magnet on a maglev vehicle vibrate and heats up inside under the influence of various disturbances in running. We have investigated the characteristics of heating in the superconducting magnet vibrating under the electro-magnetic disturbance from the ground coils. This magnetic disturbance has a frequency component ranging widely from 0 Hz to several hundred Hz which is proportional to the speed of the maglev vehicle. It was revealed that an extreme increase of heat load on the inner vessel of the energized magnet occurred at a particular frequency and it surpassed the capacity of the refrigerator installed in the tank of the superconducting magnet. As a result of the investigation, we could identify broadly three factors of heating, and now we have good prospects of largely suppressing the heating by reducing the disturbance through the folded arrangement of the ground coils and a structural improvement of the magnet.