The generation and reduction reaction of magnesium plasma were studied using a cylindrical transverse magnetic-mode applicator in magnetic and electric field modes. By heating Mg powder using the magnetic field mode, plasma was generated with the evaporation of Mg and stably sustained. When the Mg plasma sample was introduced into the reaction zone and exposed to microwave and lamp heating, a reduction reaction of scandium oxide also occurred. The results of this study provide prospects for the development of a larger microwave refining system.

This paper theoretically presents that a terahertz (THz) oscillator using a resonant tunneling diode (RTD) and a rectangular cavity, which has previously been proposed, can radiate high output power by the impedance matching between RTD and load through metal-insulator-metal (MIM) capacitors. Based on an established equivalent-circuit model, an equation for output power has been deduced. By changing MIM capacitors, a matching point can be derived for various sizes of rectangular-cavity resonator. Simulation results show that high output power is possible by long cavity. For example, a high output power of 5 mW is expected at 1 THz.

This paper presents a theoretical design of novel THz bandpass filters composed of M-PhC (metallic-photonic-crystal) point-defect-cavities (PDCs) with a centrally-loaded-rod. After a brief review of the properties of the recently-proposed M-PhC PDCs, two inline-type bandpass filters are synthesized in terms of the coupling matrix theory. The FDTD simulation results of the synthesized filters are in good agreement with the theoretical ones, which confirms the validity of the proposed filters' structures and the design scheme.

Properties of a class of M-PhC (metallic-photonic-crystal) point-defect-cavities (PDCs) with a centrally-loaded rod are theoretically and experimentally investigated. After the computation of the resonant frequencies and Q-factors of the resonant modes, the PDCs are fabricated and experimentally measured to validate the simulation results.

In this paper, we applied cavity resonator wireless power transfer (CR WPT) to an enclosed space with scatterers and revealed that high transfer efficiency at line-of-sight (LOS) and non-line-of-sight (NLOS) position in the power transmitter can be achieved by this method. In addition, we propose a method for limiting the wireless power transfer space utilizing metal mesh and show its effectiveness by experiment. First, we confirm that the constructed experimental model is working as a cavity resonator by theoretical formula and electromagnetic field analysis. Next, we calculate the maximum power transfer efficiency using a model including a plurality of scatterers by installing a power receiver at LOS and NLOS positions in the power transmitter, and it was confirmed that transfer efficiency of 30% or more could be expected even at the NLOS position. Then, we measured the frequency characteristics of a model in which one surface of the outer wall was replaced with a metal mesh, and it was clarified that the characteristics hardly changed in the power transfer frequency band. Finally, we confirmed that simultaneous communication can be performed with driving of the battery-less sensor by CR WPT, and clarify effectiveness of the proposed method.

Detection of cavities in X-ray astronomical images has become a field of interest, since the flourishing studies on black holes and the Active Galactic Nuclei (AGN). In this paper, an approach is proposed to detect cavities in X-ray astronomical images using our newly designed Granular Convolutional Neural Network (GCNN) based classifiers. The raw data are firstly preprocessed to obtain images of the observed objects, i.e., galaxies or galaxy clusters. In each image, pixels are classified into three categories, (1) the faint backgrounds (BKG), (2) the cavity regions (CAV), and (3) the bright central gas regions (CNT). And the sample sets are then generated by dividing large images into subimages with a window size according to the cavities' scale. Since the number of BKG samples are far more than the other types, to achieve balanced training sets, samples from the major class are split into subsets, i.e., granule. Then a group of three-convolutional-layer granular CNN networks without subsampling layers are designed as the classifiers, and trained with the labeled granular sample sets. Finally, the trained GCNN classifiers are applied to new observations, so as to estimate the cavity regions with a voting strategy and locate them with elliptical profiles on the raw observation images. Experiments and applications of our approach are demonstrated on 40 X-ray astronomical observations retrieved from chandra Data Archive (CDA). Comparisons among our approach, the β-model fitting and the Unsharp Masking (UM) methods were also performed, which prove our approach was more accurate and robust.

Compact and room-temperature operable terahertz emitting devices have been proposed using a semiconductor coupled multilayer cavity that consists of two functional cavity layers and three distributed Bragg reflector (DBR) multilayers. Two cavity modes with an optical frequency difference in the terahertz region are realized since two cavities are coupled by the intermediate DBR multilayer. In the proposed device, one cavity is used as the active layer for two-color lasing in the near-infrared region by current injection and the other is used as the second-order nonlinear optical medium for difference-frequency generation of the two-color fundamental laser light. The control of the nonlinear polarization by face-to-face bonding of two epitaxial wafers with different orientations is quite effective to achieve bright terahertz emission from the coupled cavity. In this study, two-color emission by optical excitation was measured for the wafer-bonded GaAs/AlGaAs coupled multilayer cavity containing self-assembled InAs quantum dots (QDs). We found that optical loss at the bonding interface strongly affects the two-color emission characteristics when the bonding was performed in the middle of the intermediate DBR multilayer. The effect was almost eliminated when the bonding position was carefully chosen by considering electric field distributions of the two modes. We also fabricated the current-injection type devices using the wafer-bonded coupled multilayer cavities. An assemble of self-assembled QDs is considered to be desirable as the optical gain medium because of the discrete nature of the electronic states and the relatively wide gain spectrum due to the inhomogeneous size distribution. The gain was, however, insufficient for two-color lasing even when the nine QD layers were used. Substituting two types of InGaAs multiple quantum wells (MQWs) for the QDs, we were able to demonstrate two-color lasing of the device when the gain peaks of MQWs were tuned to the cavity modes by lowering the operating temperature.

Many important problems in communication networks, transportation networks, and logistics networks are solved by the minimization of cost functions. In general, these can be complex optimization problems involving many variables. However, physicists noted that in a network, a node variable (such as the amount of resources of the nodes) is connected to a set of link variables (such as the flow connecting the node), and similarly each link variable is connected to a number of (usually two) node variables. This enables one to break the problem into local components, often arriving at distributive algorithms to solve the problems. Compared with centralized algorithms, distributed algorithms have the advantages of lower computational complexity, and lower communication overhead. Since they have a faster response to local changes of the environment, they are especially useful for networks with evolving conditions. This review will cover message-passing algorithms in applications such as resource allocation, transportation networks, facility location, traffic routing, and stability of power grids.

This paper proposes a blind, inaudible, robust digital-audio watermarking scheme based on singular-spectrum analysis, which relates to watermarking techniques based on singular value decomposition. We decompose a host signal into its oscillatory components and modify amplitudes of some of those components with respect to a watermark bit and embedding rule. To improve the sound quality of a watermarked signal and still maintain robustness, differential evolution is introduced to find optimal parameters of the proposed scheme. Test results show that, although a trade-off between inaudibility and robustness still persists, the difference in sound quality between the original and the watermarked one is considerably smaller. This improved scheme is robust against many attacks, such as MP3 and MP4 compression, and band-pass filtering. However, there is a drawback, i.e., some music-dependent parameters need to be shared between embedding and extraction processes. To overcome this drawback, we propose a method for automatic parameter estimation. By incorporating the estimation method into the framework, those parameters need not to be shared, and the test results show that it can blindly decode watermark bits with an accuracy of 99.99%. This paper not only proposes a new technique and scheme but also discusses the singular value and its physical interpretation.

An efficient sharply bent waveguide with a microcavity constructed by an air-bridge type two-dimensional photonic crystal slab is analyzed. The method of solution is the three-dimensional finite difference time domain (FD-TD) method. The bent waveguide has a microcavity structure that connects to an input and an output waveguide ports. The radius and position of air-holes surrounding the microcavity are modified to adjust the resonant frequency to the single-mode regime of the waveguides. It is confirmed that input optical power is transmitted efficiently to the output waveguide due to resonant tunneling caused by the microcavity.

Toward the actualization of an automatic navigation system for fetoscopic tracheal occlusion (FETO) surgery, this paper proposes a 3D ultrasound (US) calibration-based approach that can locate the fetal facial surface, oral cavity, and airways by a registration between a 3D fetal model and 3D US images. The proposed approach consists of an offline process and online process. The offline process first reconstructs the 3D fetal model with the anatomies of the oral cavity and airways. Then, a point-based 3D US calibration system based on real-time 3D US images, an electromagnetic (EM) tracking device, and a novel cones' phantom, computes the matrix that transforms the 3D US image space into the world coordinate system. In the online process, by scanning the mother's body with a 3D US probe, 3D US images containing the fetus are obtained. The fetal facial surface extracted from the 3D US images is registered to the 3D fetal model using an ICP-based (iterative closest point) algorithm and the calibration matrices, so that the fetal facial surface as well as the oral cavity and airways are located. The results indicate that the 3D US calibration system achieves an FRE (fiducial registration error) of 1.49±0.44mm and a TRE (target registration error) of 1.81±0.56mm by using 24 fiducial points from two US volumes. A mean TRE of 1.55±0.46 mm is also achieved for measuring location accuracy of the 3D fetal facial surface extracted from 3D US images by 14 target markers, and mean location errors of 2.51±0.47 mm and 3.04±0.59 mm are achieved for indirectly measuring location accuracy of the pharynx and the entrance of the trachea, respectively, which satisfy the requirement of the FETO surgery.

The equivalent circuit of aperture-coupled cavities filled with a lossy dielectric is considered by means of an eigenmode expansion technique founded on the segmentation concept. It is different from a series LCR resonant circuit, and the resistor which symbolizes the dielectric loss is connected to the capacitor in parallel. If the cavities are formed by a short-circuited oversize waveguide, then the input admittance can be represented by the product of a coupling factor to the connected waveguide port and the equivalent admittance of the short-circuited waveguide. The transmission line model is effective even if lossy wall effect and dielectric partially-loading effect are considered. As a result, three-dimensional eigenmode parameters, such as the resonant frequency and the Q-factor, become dispensable and the computational complexity for the cavity simulation in the field of microwave heating is dramatically reduced.

An efficient 12 optical power splitter constructed by a two-dimensional photonic crystal has been analyzed using the finite difference time domain (FD-TD) method. The power splitter has a microcavity which is coupled to an input and two output waveguides. We have confirmed that all optical power is transmitted into output waveguides due to resonant tunneling caused by the microcavity.

We present the theory and experiment of metal-cavity nanolasers and nanoLEDs flip-chip bonded to silicon under electrical injection at room temperature. We first review the recent progress on micro- and nanolasers. We then present the design rule and our theoretical model. We show the experimental results of our metal-cavity surface-emitting microlasers and compare with our theoretical results showing an excellent agreement. We found the important contributions of the nonradiative recombination currents including Auger recombination, surface recombination, and leakage currents. Finally, experimental demonstration of electrical injection nanoLEDs toward subwavelength nanoscale lasers is reported.

A novel half mode elliptic substrate integrated waveguide (HMESIW) filter with bypass coupling substrate integrated circular cavity (BCSICC) is proposed and fabricated by using standard PCB technology. Due to the use of an elliptical waveguide cavity, the tolerance sensitivity of the filter is reduced. The filter optimizing procedure is therefore simplified. The measured results demonstrate its superior performance in tolerance sensitivity and show good agreements with the simulation results.

Efficient silicon-based light sources are expected to be key devices for applications such as optical interconnection. Huge number of researches has been conducted for realizing silicon-based light sources. Most of them utilized silicon-related materials such as silicon nanostructures or germanium, not crystalline silicon, which has been considered as a poor light emitter because of its indirect electronic bandgap. Light emission properties of materials can be tailored not only by modifying the material properties directly, but also by controlling the electromagnetic environment surrounding the material. Photonic nanostructures are a powerful tool for creating the engineered environment. In this paper, we briefly review the mechanisms for improving the light emission properties of materials by photonic nanostructures and present our recent experimental results showing the enhancement of light emission from silicon by introducing photonic crystal structures.

A 100 GHz grooved circular empty cavity is proposed for the low loss dielectric substrate measurements by the cut-off circular waveguide method in W band. The influence of the excitation holes for the coaxial cable with a small loop are revealed by an FEM based 3D electromagnetic simulator. And also, the diameter of the excitation hole is determined based on the calculated results and the manufacturing accuracy. Then, two kinds of four 100 GHz grooved circular empty cavities are fabricated. Comparative experiments of the cavities with the different excitation holes validate the simulated results. Moreover, the complex permittivity of a PTFE plate is measured using the fabricated four cavities by the cut-off circular waveguide method around 84 GHz. The measured results agree within measurement error about 0.5% for εr and 5% for tanδ. Also, these results accord with results measured by the Whispering-Gallery mode resonator method in 85–110 GHz band. It verifies that the proposed 100 GHz cavity for the cut-off waveguide method is useful for the complex permittivity measurement of low loss dielectric substrates in W band.

A new kind of 3D power divider based on a half-mode substrate integrated circular cavity (HSICC) is proposed. This novel power divider can reduce the size of a power divider based on normal substrate integrated circular cavity (SICC) by nearly a half. To verify the validity of the design method, a two-way X-band HSICC power divider using low temperature co-fired ceramic (LTCC) technology is designed, fabricated and measured.

A dominant-mode rectangular cavity antenna design yielding an improved bandwidth is experimentally verified. Simple field theories indicate that extending the aperture height should increase the antenna bandwidth without shifting the operation frequency. Antenna samples built from a 4.4 dielectric constant material produce 3-dB efficiency bandwidths of 15 and 23 percent for the respective cavity height-to-width ratios of 0.5 and 0.75 at 7 GHz.

Bandwidth and gain enhancement of microstrip patch antennas (MPAs) is proposed using reflective metasurface (RMS) as a superstrate. Two different types of the RMS, namely- the double split-ring resonator (DSR) and double closed-ring resonator (DCR) are separately investigated. The two antenna prototypes were manufactured, measured and compared. The experimental results confirm that the RMS loaded MPAs achieve high-gain as well as bandwidth improvement. The desinged antenna using the RMS as a superstrate has a high-gain of over 9.0 dBi and a wide impedance bandwidth of over 13%. The RMS is also utilized to achieve a thin antenna with a cavity height of 6 mm, which is equivalent to λ/21 at the center frequency of 2.45 GHz. At the same time, the cross polarization level and front-to-back ratio of these antennas are also examined.