Photonic-crystal surface-emitting lasers (PCSELs) are attractive for a wide range of applications such as material processing and remote sensing owing to their advantage of broad-area coherent lasing supported by a 2-D photonic crystal. Recently, we proposed double-lattice photonic-crystal resonators and achieved 10-W-class high-power and high-beam-quality (namely, high-brightness) operation. To further increase the brightness, it is important to understand the lasing mode behavior of PCSELs in detail. In this article, we experimentally investigate the change in the lasing mode depending on the current injection levels and compare the results with a theoretical analysis that accounts for the change in refractive index and gain distributions due to the current injection. We observed a transition from single-mode lasing to two-mode lasing at high injection currents. We develop a technique for resolving the near-field profiles of individual lasing modes and show that these profiles coincide with theoretical predictions. A comparison of experimental and theoretical results reveals that high-order modes appear due to a bandgap confinement effect induced by a change in the refractive index in the carrier injection area. To effectively remove this confinement effect and suppress the oscillation of high-order modes, we incorporate an in-plane heterostructure into the PCSEL.

In-band full-duplex, allowing simultaneous transmission and reception on the same device over the same frequency, can double the spectral efficiency theoretically. However, the severe self-interference challenges the physical layer design. Thus, to simplify the interference cancellation (IC), the space division full-duplex (SDFD) is considered, where two spatial-separated transmission points (TPs), e.g., base stations, simultaneously serve the same cell in downlink (DL) and uplink (UL), respectively. In this paper, assuming the TP has digital-domain IC capability only, we study the SDFD scheme in heterogeneous network, i.e., a small cell (named SDFD-cell) is served as SDFD via macro TP (MTP) in DL and small TP (STP) in UL. Due to the inter-TP interference, the capacity of SDFD-cell is restricted by the digital-domain IC. Moreover, SDFD degrades the performance of other non-SDFD-cells. Therefore, we propose a joint scheduling and precoding design algorithm. The scheduling scheme selects a user equipment (UE) pair in the SDFD-cell for DL and UL transmissions as proportional fairness metric. Then, an optimal precoder is designed for MTP to reduce the interference in both SDFD-cell and non-SDFD-cells. The simulation results verify that the proposed algorithm can significantly improve the capacity of the SDFD-cell with limited capacity degradation in non-SDFD-cells.

The authors measured electroencephalograms (EEGs) from subjects looking at line drawings of body parts and recalling their names silently. The equivalent current dipole source localization (ECDL) method is applied to the event related potentials (ERPs): summed EEGs. ECDs are localized to the primary visual area VI, to the ventral pathway (ITG: Inferior Temporal Gyrus), to the parahippocampus (ParaHip), the right angular gyrus (AnG), to the right supramarginal gyrus (SMG) and to the Wernike's area. Then ECDs are localized to the Broca's area, to the postcentral gyrus (PstCG) and to the fusiform gyrus (FuG), and again to the Broca's area. These areas are related to the integrated process of visual recognition of pictures and the retrieval of words. Some of these areas are also related to image recognition and word generation. And process of search and preservation in the memory is done from the result of some ECDs to the paraHip.

Human beings cannot control a position of sphere on the disk without seeing it. Because under such a condition, as we determine the position and estimate the motion of sphere by use of visual information, it is very difficult for human beings to control it using only tactile or force information of a hand. This is why the tactile and the force information are less quantitative for human beings than the visual information. On the other hand, a robot can deal with this qualitative information as quantitative values. Therefore, the robot seems to have the possibility that it carries out such difficult tasks for human beings using only force information. In this paper, we propose the estimation method of the position of sphere (made of crystal) on the disk from the force information measured with three-directional force sensors. Then, we tried to examine whether the robot fingers can control the motion of sphere on the disk using only these force information. Actually, the position and the velocity information estimated from force information enable the robot fingers to control the sphere by applying a simple PD control algorithm. Moreover, this paper adds Lyanpunov’s stability analysis of the proposed control algorithm. Finally, this results show new robot task which human beings cannot realize, whose demonstration is very interesting.

Proposes two efficient excitation coding schemes that use a pitch synchronous two-dimensional Fourier transform of linear prediction residual signals. One quantizes and transmits part of the 2D transform coefficients. Transmission of only low transition frequency coefficients results in less perceivable quantization distortion with fewer quantization bits. The other coding scheme is prototype waveform interpolation (PWI) coding using smoothed prototype waveforms. A frequency domain prototype waveform smoothing technique improves the perceptual speech quality of conventional PWI coding. A simulation result of a 1900 bps proposed vocoder is presented. The authors also present a multiband excitation approach for the proposed PWI coding scheme to further improve quality.>

The authors present a structured codebook for reducing the complexity and memory of a CELP stochastic codebook search. The tree-structured delta codebook, whose code vectors are generated from a small number of delta vectors, can be searched efficiently by calculating the vector correlations recursively. The complexity was reduced to 1/70 that of a conventional full-Gaussian codebook, and the memory for codebook storage was reduced to 1/100. Another excellent feature of this codebook is the feasibility of changing the distribution of code vectors adaptively. The codebook adaptation method (delta vector sorting) provides an SNRseg improvement of 0.6 dB, and consistent improvement in perceptual quality, by changing the order of delta vectors to fit the input speech.>

Principal axis extracting vector excitation coding (PAVXC) is proposed in which an efficient codebook search method and an improved excitation modeling technique are used. A two-step codebook search using a small-size codebook of 20 dimensions (half the conventional size) can reduce the computational complexity by a factor of 64, maintaining the reproduced speech quality within a slight degradation of 0.9 dB in SNR seg. Multiple vector excitation using an impulse vector jointly with the conventional stochastic code vector can provide more precise representation of the excitation. The impulse vector is extracted from each code vector by principal axis extraction, and its gain is jointly optimized with the gain for the code vector. The improvement in SNR seg is 1.2 dB, which compensates for the degradation caused by the two-step codebook search. The quality of the reproduced speech using PAVXC is subjectively much better than that of conventional VXC, thanks especially to the improvement in voiced regions.>