Dynamic range and sensitivity adaptation in a silicon spikingneuron

We propose an adaptive procedure that enables a spiking neuron, whether artificial or biological, to make optimal use of its dynamic range and gain. We discuss an analog electronic circuit implementation of this algorithm using a biologically realistic artificial "silicon" neuron. The adaptation procedure adapts the neuron's firing threshold and the sensitivity (or gain) of its current-frequency relationship to match the DC offset (or mean) and the dynamic range (or variance) of the time-varying somatic input current. The neuron extracts the minimum and maximum levels of the reconstructed somatic current signals from the cell's own spike trains. These are used to regulate the somatic leak conductance in order to shift the somatic current-frequency relation and to adjust a calcium-activated potassium conductance to change the dynamic range of the cell's somatic current-frequency relationship. We report experimental data from a test neuron-built using analog subthreshold CMOS VLSI technology-that shows the expected behavior.     

Studies on a LaF3‐coated MgO protecting layer in AC‐plasma‐display panels

A new protecting layer, a LaF₃‐coated MgO layer, in color AC‐plasma‐display panels (PDPs) was studied in order to overcome the weakness of the conventional single MgO protecting layer. The material characteristics of the new layer were examined by using variations in the deposition process. The display characteristics were also examined by implementing their processes to actual PDPs. It was demonstrated that this method is effective in lowering the firing and sustaining voltages of PDPs and enhancing the brightness of the panel as well.     

A global structural optimization technique using an interval method

This paper deals with a global optimization scheme for structural systems that require finite element analysis to evaluate the constraints or the objective function. The paper proposes a strategy for finding the global optimum using an interval method in conjunction with a multipoint function approximation. The highly nonlinear and nonconvex objective and constraint functions are first represented in the design space using linear and adaptive local approximations and these approximations are blended globally with the use of proper weighting functions. The interval method is then employed to trace the global optimum in the approximated function space. The procedure is tested with several examples with known global solutions and it is successfully applied to optimize the fiber-orientation angles of laminated composite plates for minimum deflections. Received December 22, 2000     

Multiagent reinforcement learning applied to a chase problem in a continuous world

Reinforcement learning (RL) is one of the methods of solving problems defined in multiagent systems. In the real world, the state is continuous, and agents take continuous actions. Since conventional RL schemes are often defined to deal with discrete worlds, there are difficulties such as the representation of an RL evaluation function. In this article, we intend to extend an RL algorithm so that it is applicable to continuous world problems. This extension is done by a combination of an RL algorithm and a function approximator. We employ Q-learning as the RL algorithm, and a neural network model called the normalized Gaussian network as the function approximator. The extended RL method is applied to a chase problem in a continuous world. The experimental result shows that our RL scheme was successful. This work was presented in part at the Fifth International Symposium on Artificial Life and Robotics, Oita, Japan, January 26–28, 2000     

Real-time transport of MPEG video with a statistically guaranteedloss ratio in ATM networks

Unlike deterministic real-time communication in which excessive resources may be required for “absolute” performance guarantees, statistical real-time communication seeks to achieve both probabilistic performance guarantees and efficient resource sharing. This paper presents a framework for statistical real-time communication in ATM networks, providing delay-guaranteed transport of MPEG-coded video traffic with a statistically-guaranteed cell-loss ratio. Delay-guaranteed communication is achieved with a modified version of Traffic-Controlled Rate-Monotonic Priority Scheduling (TCRM). A set of statistical real-time channels that share similar traffic characteristics are multiplexed into a common macrochannel. Those statistical real-time channels which are multiplexed together share the resources of a macrochannel, and individual statistical real-time channels are given timeliness and probabilistic cell-loss guarantees. A macrochannel is serviced by the modified TCRM which improves link utilization and makes channel management simpler. Based on the analysis of an M/D/1/N queueing system, we propose a procedure for determining the transmission capacity of a macrochannel necessary to statistically guarantee a cell-loss ratio bound. Our extensive trace-driven simulation has shown the superiority of the proposed framework to the other approaches. The overall cell-loss ratios for multihop statistical real-time channels are shown to be smaller than the predetermined bounds, thus verifying our analytical results     

Computation of hydrostatic piezoelectric coefficients for 1–3 composites by the finite-element method

The hydrostatic piezoelectric charge coefficients (d_h) and hydrostatic piezoelectric voltage coefficients (g_h) of 1–3 PZT/polymer composites have been calculated by two equations containing the stress tensors of each element. A composite model is divided into 162 elements, and the stress distributions are computed under 0.7 MPa hydrostatic pressure using the finite-element method. The higher d_h value is found for the composite with 30.9% PZT and the higher g_h value for the composite with 19.8% PZT.     

Generation and Control of Game Virtual Environment

In this paper,we present a framework for the generation and control of an Internet-based 3-dimensionai game virtual environment that allows a character to navigate through the environment.Our framework includes 3-dimensional terrain mesh data processing,a map editor,scene processing,collision processing,and waikthrough control.We also define an environment-specific semantic information editor,which can be applied using specific location obtained from the real world.Users can insert text information related to the characters real position in the real world during navigation in the game virtual environment.     

Interactive classification for pre-integrated volume rendering of high-precision volume data

The pre-integrated volume rendering technique is widely used for creating high quality images. It produces good images even though the transfer function is nonlinear. Because the size of the pre-integration lookup table is proportional to the square of data precision, the required storage and computation load steeply increase for rendering of high-precision volume data. In this paper, we propose a method that approximates the pre-integration function proportional to the data precision. Using the arithmetic mean instead of the geometric mean and storing opacity instead of extinction density, this technique reduces the size and the update time of the pre-integration lookup table so that it classifies high-precision volume data interactively. We demonstrate performance gains for typical renderings of volume datasets.     

Generating useful images for medical applications from the Visible Korean Human

For the Visible Korean Human (VKH), a male cadaver was serially ground off to acquire the serially sectioned images (SSIs) of a whole human body. Thereafter, more than 700 structures in the SSIs were outlined to produce detailed segmented images; the SSIs and segmented images were volume- and surface-reconstructed to create three-dimensional models. For outlining and reconstruction, popular software (Photoshop, MRIcro, Maya, AutoCAD, 3ds max, and Rhino) was mainly used; the technique can be reproduced by other investigators for creating their own images. For refining the segmentation and volume reconstruction, the VOXEL-MAN system was used. The continuously upgraded technique was applied to a female cadaver's pelvis to produce the SSIs with 0.1mm sized intervals and 0.1mm x 0.1mm sized pixels. The VKH data, distributed worldwide, encouraged researchers to develop virtual dissection, virtual endoscopy, and virtual lumbar puncture contributing to medical education and clinical practice. In the future, a virtual image library including all the Visible Human Project data, Chinese Visible Human data, and VKH data will hopefully be established where users will be able to download one of the data sets for medical applications.