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In the development of inter-vehicle communication systems for the prevention of car crashes, it is important to know radio propagation characteristics at blind intersections. In field experiments and numerical simulations to investigate radio propagation characteristics, a half wavelength dipole antenna is assumed to be the wave source in many cases. However, a directivity of car antenna is changed by the effect of both car body and antenna position on car. In this paper, path loss characteristics considering antenna positions on car body at a blind intersection in urban area for inter-vehicle communications using 700MHz band are investigated. Additionally, simplified car models are proposed for the efficient analysis of radio propagation. Here, the hybrid method using both FDTD and ray-tracing methods is used for the radio propagation analysis.

Hyalinizing clear cell carcinoma (HCCC) is a rare, low-grade salivary gland neoplasm with a predilection for the palate and tongue. A 63-year-old woman presented a 14×14×17-mm mass at the roof of the nasopharynx. Endoscopic resection was performed via a transnasal approach. Histopathological findings of the salivary gland tumor indicated hyalinization of the stroma and neoplastic cells with clear cytoplasm without mucin. Fluorescence in situ hybridization analysis revealed that the tumor cells were positive for EWSR1 rearrangement. We finally diagnosed this case as HCCC of the nasopharynx. EWSR1 rearrangements are non-existent in other salivary gland tumors with clear cell change; thus, the identification of this rearrangement was very useful in accurately diagnosing HCCC.

It is important to know distance dependence of electric field pattern to measure radiation patterns for car mounted antennas. In this article, the distance dependence of electric field pattern for an antenna mounted on a car in the UHF band is investigated by the electromagnetic simulation for the first time. As a result, it is shown that the distance dependence of electric field pattern is affected by polarization, frequency, antenna positions, and origin positions to define the distance. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2182–2186, 2013

Although we have evaluated the characteristics of the FM receiver by repeated running tests. Thus, there have been issues in its reproducibility and objectivity. To solve this problem, we developed a Two-Stage method reproducing a virtual radio environment on a PC [1]. However the Two-Stage method also had problems in estimating the actual radio wave environment and the arrival of FM broadcast wave. Thus, estimation of incoming waves by experiment is necessary by using the likes of MUSIC (Multiple Signal Classification) method [2]. However, application of MUSIC method to FM reception has an issue in the separation performance for multipath waves in urban area due to constraints such as the number of array antenna elements. Consequently, MUSIC method with the use of virtual array antennas was developed [3]. In this study, the accuracy of MUSIC method-based estimation in actual environment was verified by modeling actual reception environment in urban area, and calculating values regarding radio wave environment characteristics with the use of a 3D map and ray tracing method.

In the radio propagation analysis, it is expected that the FDTD method becomes a counterpart of ray-tracing method by using the direction of arrival (DOA) estimation method. However, characteristics of DOA estimation in the FDTD analysis are not clear. In this paper, the accuracy of DOA estimation in the FDTD analysis of radio propagation using the multiple signal classification (MUSIC) method is investigated.

An inter-vehicle communication system for the 720MHz band that is designed to prevent car crashes at intersections has recently been proposed in Japan. This paper presents an analysis of the propagation characteristics of an intersection surrounded by concrete block walls in a residential area. The propagation characteristics were analyzed for the first time using the finite-difference time-domain (FDTD) method. We investigated the influence of wall thickness and source locations on the propagation characteristics. The results of our investigation showed that the most commonly used wall thickness and source locations do not strongly affect propagation loss. Furthermore, we analyzed the power delay profile and delay spread by taking into consideration the structure of the concrete block walls.

In our previous work, we engaged in vehicle navigations system with UHF RF-ID system against low visible condition. During the winter, northern part of Japan, driving lane is covered with snow and ice and we sometime meet heavy snowfall. Occasionally, some drivers go out from their driving lane in low visible condition caused by snow storm. Our navigation system is made to prevent such traffic accidents with low visible condition. There are several studies related on lane departure warning and vehicle positioning with GPS, DSRC, and other technique. These systems have virtues and weakness for our circumstance. In this paper, we will discuss vehicle navigation for turn action in the intersection with data stored driving lane and related issues.

In the development of the inter-vehicle communication systems for the prevention of car crashes, it is important to know radio propagation characteristics at blind intersections. In field experiments and numerical simulations to investigate radio propagations, a half wavelength dipole antenna is assumed to be the wave source in many cases. However, the directivity of car antenna is changed by effects of car body and antenna positions on car body. Therefore, it is necessary to investigate effects of car antenna positions on radio propagation characteristics at blind intersections. In this paper, propagation loss characteristics considering car antenna position for inter-vehicle communications using 700 MHz band at a blind intersection is investigated. Here, the hybrid method using both the FDTD and ray-tracing methods is used for the electromagnetic analysis.

In the development of the inter-vehicle communication systems for the prevention of car crashes, it is important to know characteristics of radio wave propagation at blind intersections. In the analysis of radio propagation characteristics, a λ/2 dipole antenna is assumed to be the wave source in many cases. However, it is necessary to analyze radio propagation characteristics considering the car body. The reason why is that the directivity of car antenna is changed due to the effect of car body. Additionally, the directivity of car antenna is also changed by the effect of antenna position on car body. In this paper, the effect of car antenna position on radio propagation characteristics at a blind intersection is investigated. Here, the hybrid method using both the FDTD and ray-tracing methods is used for the electromagnetic analysis.

Magnetic excitations in the cooperative ordered state in a weakly coupled Fe chains and Cu dimers compound Cu{sub 2}Fe{sub 2}Ge{sub 4}O{sub 13} is studied by thermal neutron scattering technique. We show that the low energy excitations up to 10 meV in wide q range are well described by spin wave theory of weakly coupled Fe chains. In higher energy range a narrow band excitation that can be associated with Cu dimers is observed at {Dirac_h}{omega}-24 meV. Both types of excitations can be understood by treating the weak coupling between Fe chains and Cu dimers at the level of Mean Field/Random Phase Approximation.

The structure of Cu 2 Fe 2 Ge 4 O 13 , previously thought to be CuFeGe 2 O 6 , has been determined from single-crystal X-ray diffraction data to be monoclinic, P 2 1 / m , a =12.1050(6), b =8.5073(4), c =4.8736(2) A, β =96.145(1)°, Z =2, with R 1=0.0231 and w R 2=0.0605. The unique structure has an oligomer of four germanate tetrahedra, cross-linked laterally by square-planar copper ions, joined end-to-end by a zigzag chain of edge-sharing iron oxide octahedra. Running along the a -direction the metal oxide chain consists of alternating Cu–Cu and Fe–Fe dimers. A hypothetical series of homologous structures (Cu n −2 Fe 2 Ge n O 3 n +1 with n =3,4,…,∞) with different length germanate oligomers is proposed, where as n increases, the infinite chain of the CuGeO 3 is approached. In this context, Cu 2 Fe 2 Ge 4 O 13 is viewed as being built from blocks of CuGeO 3 and the Fe oxide chains. This material has significance to the study of low-dimensional mixed-spin systems.

We have demonstrated multi-wavelength VCSEL array operating at 1060nm with dielectric phase tuning layers. Uniform threshold currents of approximately 0.35mA were successfully realized over 16 channels (10nm wavelength span) by only four-step lithography and etching.

Recently, the inter-vehicle communication systems have been proposed for the prevention of car crash. By the way, a radiation pattern of car antenna is changed by effects of car body and antenna positions. Therefore, it is important to know the influence of car body and antenna positions on radio wave propagation characteristics. In the numerical simulation, from a viewpoint of the reduction of computational cost, it is interested to consider a simplified car model that can obtain reasonable numerical results. In this paper, effects of car body on radiation pattern of car antenna mounted on a side mirror for inter-vehicle communications are investigated. As a first step in this work, both strict and simplified models of car body are considered. As the numerical simulation method, the FDTD method is used.

It is important to know distance characteristics of electric field pattern to measure radiation patterns for car mounted antennas. In this paper, distance characteristics of electric field pattern for an antenna mounted on a car in the UHF band are investigated by the electromagnetic simulation for the first time. As a result, it is shown that distance characteristics of electric field pattern are affected by polarization, frequency, antenna positions, and origin positions to define the distance.

In Japan, an inter-vehicle communication system using the 720 MHz band has been proposed to prevent car crashes at intersections. This study analyzes the propagation characteristics in an intersection surrounded by compound walls in a residential area. We investigated the qualitative impact of the wall thickness and height and the ground on the propagation characteristics for the first time by using the finite-difference time-domain (FDTD) method. The results showed that the wall thickness and height affect the propagation characteristics.

This paper reviews research and development of 1060nm VCSELs at Furukawa Electric. We pursue the simultaneous realization of three strong demands for low power consumption, high reliability, and high speed. For this purpose, we have chosen compressively strained InGaAs/GaAs active layers emitting in a 1060 nm wavelength range because of their advantages of lower threshold voltage, smaller defect propagation velocity, and larger material differential gain, compared to those of GaAs/AlGaAs active layers widely used in 850 nm VCSELs. Oxide-confined and double intracavity structures provide low and stable electrical resistance as well as low optical loss. The developed VCSELs exhibited low threshold currents of 0.31 mA at 25 °C and 0.56 mA at 90 °C, together with highly uniform slope efficiency distributions throughout a wafer. We also demonstrated 10 Gbps error free transmission at a very low bias current of 1.4 mA, yielding low power dissipation operation of 0.14 mW/Gbps. Clear eye openings up to 20 Gbps were confirmed at a low bias current of 3mA. A series of endurance tests and accelerated aging tests on nearly 5000 VCSELs have proved Telcordia qualified high reliability and a very low failure rate of 30 FIT/channel at an operating temperature of 40 °C and a bias current of 6mA, with a 90% confidential level.

Furukawa's 1060nm VCSELs with double-intra-cavity structure and Al-free InGaAs/GaAs QWs enable us to realize low power consumption, high speed operation and high reliability simultaneously. The power dissipation was as low as 140fJ/bit. Clear eye opening up to 20Gbps was achieved. Random failure rate and wear-out lifetime were evaluated as 30FIT/channel and 300 years. For higher speed operation, thickness of oxidation layer was increased for lower parasitic capacitance of device. Preliminary reliability test was performed on those devices. In high speed operation faster than 10Gbps, conventional lifetime definition as 2dB down of output power is not sufficient due to smaller margin of modulation characteristics. We suggest threshold current as a barometer for degradation of modulation characteristics. The threshold currents of our VCSELs degrade small enough during accelerated aging test. We also observed no remarkable change in 25Gbps eye diagram after aging test. The definition of life time for high speed VCSEL is discussed from the change in threshold current and so on in addition to the conventional power degradation during aging. It is experimentally verified that our VCSELs are promising candidate for highly reliable light source including long term stable high speed operation.

High reliability, low power consumption and high speed laser diodes are required for optical interconnect. We developed 1060nm VCSELs with InGaAs/GaAs strained quantum wells, oxide-confined and double intra-cavity structures for that purpose. As for the power consumption, low power dissipation of 0.14 mW/Gbps at 10 Gbps operation has been achieved. Clear eye openings up to 20 Gbps were confirmed at a low bias current of 5 mA. In the reliability test, accelerated aging tests were performed up to 5,000 hours at 6 mA in three different temperatures, 70 oC, 90 oC and 120 oC. The total number of the VCSELs was 4,898 pcs (approximately 5,000). No failure was observed. Under the normal operating condition of 40 oC and 6 mA, the total device-hours was 7.75×107 hours assuming Ea = 0.35 eV according to Telcordia GR-468-CORE. The random failure rate of 30 FIT with the confidence level (C.L.) of 90 % and 12 FIT with the C.L. of 60 % were estimated. To estimate the wear-out lifetime and the number of FITs, high stressed aging tests with 170 oC and 6 mA were performed. With the acceleration factor of Ea = 0.7 eV in the wear-out failure, the median lifetime was 3,000 hours which was equivalent to 300 years in 40 oC ambient. The FIT numbers due to the wear-out were estimated as 0.3 FIT for 10 years. Compared with the random failure rate of 30 FIT, the wear-out failure rates are considered to be negligible. In the extremely long term aging test with 90 oC and 6 mA, no wear-out trend has been observed in both threshold current and optical power up to 20,000 hours operation. These results indicate that 1060 nm VCSEL is promising light source used in optical interconnect for high performance computers and data centers.

State of the art VCSEL technology will be reviewed in terms of power consumption and reliability in order to realize the energy efficient HPC and Data Centers. Longer wavelength VCSEL seems promising candidate for the upcoming higher performance computes with energy saving.

The demand for the on board intra-chip optical interconnection as the "Green interconnect" have been growing so rapidly in order to catch up the speed of the performance development of high performance computing systems. In this report, our continuous study results expanding to intra-chip application in terms with power consumption and reliability are shown for the "Green" 1060nm VCSEL arrays developed by Furukawa Electric 1 . As the basic performance level, the clear eye opening up to 20Gbps was achieved with low power dissipation level of 160fJ/bit with voltage swing level of 130mVpp. This value would be considered as the same level of the 140fJ/bit in 10Gbps operation with 75mVpp. In the reliability test, our large scale FIT rate test had been reached up to 7.8E7 device hours and the estimated FIT rate of 30FIT/ch was obtained from no failure sample and confidence level of 90%. Our wear-out study was performed with high stress test of 170°C ambient temperature and estimated failure rate for 10years service time was 0.3FIT/ch for this mode. Our 1060nm VCSEL with low power consumption level of 140fJ/bit and high reliability of 30FIT/ch would be projected to a light source for intra-chip application.

1060nm VCSELs with InGaAs/GaAs strained quantum wells have been reviewed in terms of power consumption and reliability. Clear eye opening was confirmed at 10Gbps with bias current of as low as 1.4mA.

Extremely low power dissipation of 0.14 mW/Gbps at 10 Gbps operation with as small as 75 mV p-p of modulation amplitude has been achieved in carefully designed InGaAs/GaAs-MQW 1060 nm VCSELs employed double intra-cavity structure.

No systematic studies on 1060nm high speed VCSELs have been reported in terms with reliability so far to our best knowledge. In this work, a systematic and intensive study on reliability has been performed for our 1060nm VCSELs consist of double intra-cavity and oxide confined structure with >70ps eye opening margin in Ib=3mA. Estimated power dissipation per bit rate of >5Gbps/mW at Ib=2mA was obtained from low series resistance and low drive voltage characteristics due to effective current injection in our double intra-cavity structure. Aging tests for 3,467pcs discrete non-hermetic VCSELs were performed under 6mA, 70°C to 120°C and up to 5,736 hours, which is equivalent to over 10million device hours in normal operating condition of 40°C and Ib=5mA. We found one degraded device due to the disconnection of the metal interconnecting layer, resulting in 8lFits (C.L.=90%) under Ea=0.35eV and no current accelerated factor. Also, their degradation of threshold current after 1,000 hours operation was less than 0.1mA under high stress condition of >40kA/cm 2 and 120°C, which corresponds to more than hundreds year operation. No eye diagram degradation was observed as far as no large threshold current increase under the high stress condition up to 40kA/cm 2 . It is experimentally proven that inherent potentiality of the VCSELs with 1060nm InGaAs-QW and double intra-cavity structure would be applicable to the future large green data traffic system.

VCSEL performance will be reviewed. A careful design of cavity structure, as well as precise control in the epitaxial growth enables us to achieve a record power conversion efficiency of 62% in the 1060nm VCSELs.

The optical absorption coefficient (α) for carbon-doped GaAs epitaxial layer by CBr 4 with doping range from 1018 to 1020 cm−3 was measured for the first time. Obtained α GaAs:C was 2-times larger than α GaAs:Zn at 1300nm.

High efficiency VCSELs will be reviewed in terms of power conversion efficiency. Other lasing parameters will be also discussed.

VCSELs will be reviewed in terms of power conversion efficiency in this talk. In addition, high speed VCSEL and its transmitter modules for parallel optical interconnection will be presented.

Magnetic excitations in a weakly coupled spin dimers and chains compound Cu{sub 2}Fe{sub 2}Ge{sub 4}O{sub 13} are measured by inelastic neutron scattering. Both structure factors and dipsersion of low-energy excitations up to 10 meV energy transfer are well described by a semiclassical spin wave theory involving interacting Fe{sup 3+}(S=5/2) chains. Additional dispersionsless excitations are observed at higher energies, at {Dirac_h}{omega}=24 meV, and associated with singlet-triplet transitions within Cu{sup 2+} dimers. Both types of excitations can be understood by treating weak interactions between the Cu{sup 2+} and Fe{sup 3+} subsystems at the level of the mean-field random phase approximation. However, this simple model fails to account for the measured temperature dependence of the 24 meV mode.