Ichi Takumi

Experiment of indoor position presumption based on RSSI of Bluetooth LE beacon

Real-time indoor location estimation needs multiple signals from different sources. To ensure accuracy of estimation, adopting Bluetooth Low Energy (LE) beacon devices as signal sources is a reasonable solution. We have installed a number of Bluetooth Low Energy (LE) beacon devices in and around a room and observed beacons by portable devices with RSSI to achieve fundamental knowledge of beacons and feasibility of location estimation. By applying an estimation method, we have achieved over 95% of correct estimation rate and complete separation that a device is in a room or not.

Nonlinear optical properties of gold nanoparticles selectively introduced into the periodic microdomains of block copolymers.

Nonlinear-optical nanocomposite materials with a photonic crystal structure were fabricated using block copolymers and gold nanoparticles. By dispersing the gold nanoparticles into the selective microdomains of the block copolymers, we could achieve the enhancement of nonlinear optical properties as revealed by the Z-scan technique. The optical nonlinearities were enhanced by the local field effect and the effect of the periodic distribution of the microdomains filled with gold nanoparticles. Furthermore, the highest optical nonlinearity was achieved by matching the domain spacing of the copolymers with the frequency of the surface plasmon resonance peak of the gold.

A cutting-plane method based on redundant rows for improving fractional distance

In this paper, an idea of the cutting plane method is employed to improve the fractional distance of a given binary parity check matrix. The fractional distance is the minimum weight (with respect to lscr1-distance) of vertices of the fundamental polytope. The cutting polytope is defined based on redundant rows of the parity check matrix and it plays a key role to eliminate unnecessary fractional vertices in the fundamental polytope. We propose a greedy algorithm and its efficient implementation for improving the fractional distance based on the cutting plane method.

Gradient descent bit flipping algorithms for decoding LDPC codes

A novel class of bit-flipping (BF) algorithms for decoding low-density parity-check (LDPC) codes is presented. The proposed algorithms, which are called gradient descent bit flipping (GDBF) algorithms, can be regarded as simplified gradient descent algorithms. Based on gradient descent formulation, the proposed algorithms are naturally derived from a simple nonlinear objective function.

Minimum error detection of classical linear code sending through a quantum channel

Abstract It is shown that group covariant signals with respect to a specific group with the operation “Exclusive OR”, which include binary linear codes as examples, satisfy the condition of the theorem 1 in [Phys. Rev. A 58 (1998) 146] and the minimum error detection is so-called square-root measurement.

Global Noise Estimation Based on Tensor Product Expansion with Absolute Error

This paper proposes a novel signal estimation method that uses a tensor product expansion. When a bivariable function, which is expressed by two-dimensional matrix, is subjected to conventional tensor product expansion, two single variable functions are calculated by minimizing the mean square error between the input vector and its outer product. A tensor product expansion is useful for feature extraction and signal compression, however, it is difficult to separate global noise from other signals. This paper shows that global noise, which is observed in almost all input signals, can be estimated by using a tensor product expansion where absolute error is used as the error function.

Estimation of EM source location from 223 Hz EM field power data at multiple spots

Our goal is prediction of earthquakes from anomalous electro-magnetic wave radiation. For the purpose, we have been measured EM wave of 223 Hz at 40 spots in Japan. This paper presents some results of our research to estimate EM wave source locations from EM field measured at multiple measuring spots.

Superadditivity in capacity of quantum channel for q-ary linearly dependent real symmetric-state signals

An analytical expression for the mutual information is derived for q-ary pseudo-cyclic codes. We compute mutual information for 3- and 5-ary linearly dependent signals. It is shown that higher quantum gain can be achieved by 3-ary codes and 50 percent of full quantum gain is achieved even for the codeword length n=16.

AN ANOMALY OF ELF BAND VERTICAL MAGNETIC FLUX AS A PRECURSOR OF DOME FORMATION AT UNZEN VOLCANO AND ITS MODEL ANALYSIS

Abstract A peculiar environmental vertical magnetic flux anomaly was observed at the frequency of 223 Hz, which was 40 and 75 days before the 10th and 11th dome formations on Unzen volcano. The small but clear anomaly of order of 0.5 pT / Hz had appeared just on the vertical magnetic flux and never on the horizontal ones, and showed in many cases an intermittent oscillations of about a half- to 1-min period with almost the same size amplitudes. In this paper, we show a possibility that the vertical anomaly corresponds to the electromagnetic phenomena when magma passes the upper layer of aquifer under a volcano and give a simplified model which represents the phenomena and mechanism of generating the anomalous vertical magnetic flux. The anomaly lasted from the end of 1992 to September 10, 1994. After the termination of the appearance, the Unzen volcano weakened the activity and no events have been reported since then.

The precursor signal detection from electromagnetic waves for predicting great earthquakes using Kalman filter

The tectonic activities that precede significant earthquakes release electromagnetic (EM) waves that can be used as earthquake precursors. We have been observing EM radiation in the extremely low frequency band at over 40 observation stations in Japan for predicting significant earthquakes. However, the recorded signals contain several noise components generated from the ionosphere, human activity, and so on. Most background noise in observed signal is attributed to lightning in the tropics. In this paper, we introduce a state space model and Kalman filter to reduce the noise. The good performance of the proposed model is confirmed.