Transmission performance of 10-Gb/s 1550-nm transmitters using semiconductor optical amplifiers as booster amplifiers

We have demonstrated the transmission performance of 10-Gb/s transmitters based on LiNbO/sub 3/ modulator using semiconductor optical amplifiers (SOAs) as booster amplifiers. Utilizing the negative chirp converted in SOAs and self-phase modulation induced by high optical power, we can successfully transmit 10-Gb/s optical signals over 80 km through the standard single-mode fiber with the transmitter using SOAs as booster amplifiers. SOAs can be used for booster amplifiers with a careful adjustment of the operating conditions. In order to further understand an SOA's characteristics as a booster amplifier, we model SOAs and other subsystems to verify the experimental results. Based on the good agreement between the experimental and simulation results, we can find the appropriate parameters of input signals for SOAs, such as extinction ratio, rising/falling time, and chirp parameter to maximize output dynamic range and available maximum output power (P/sub o,max/).     

PASU: A personal area situation understanding system using wireless camera sensor networks

In this paper, we present a personal area situation understanding (PASU) system, a novel application of a smart device using wireless camera sensor networks. The portability of a PASU system makes it an attractive solution for monitoring and understanding the current situation of the personal area around a user. The PASU system allows its user to construct a 3D scene of the environment and view the scene from various vantage points for better understanding of the environment. The paper describes the architecture and implementation of the PASU system addressing limitations of wireless camera sensor networks, such as low bandwidth and limited computational capabilities. The capabilities of PASU are validated with extensive experiments. The PASU system demonstrates the potential of a portable system combining a smart device and a wireless camera sensor network for personal area monitoring and situation understanding.     

Visualization of Fatigue Cracks at Structural Members Using a Pulsed Laser Scanning System

In this research, a noncontact nondestructive testing (NDT) method is proposed to detect the fatigue crack and to identify the location of the damage. To achieve this goal, Lamb wave propagation of a plate-like structure, which is induced by scanning laser source actuation system, is analyzed. A ND:YAG pulsed laser system is used to generate Lamb wave exerted at the multiple points of a steel coupon, and a piezoelectric sensor is installed to measure the structural responses. Multiple time signals measured by the piezoelectric sensor are aligned along the vertical and horizontal axes corresponding to laser impinging points so that 3-dimensional data can be constructed. Then, the 3-dimensional data is sliced along the time axis to visualize the wave propagation. The scattering of Lamb wave due to the damage can be described in the wave propagation image, and hence the damage can be localized and quantified. Damage-sensitive features, which are reflected wave from the damage, are clearly extracted by wave-number filtering based on the 3-dimensional Fourier transform of the visualized data. Structural members with fatigue cracks are investigated to verify the effectiveness and the robustness of the proposed NDT approach.     

Solubility enhancement of PCDD/F in the presence of dissolved humic matter

From previous studies, we, the authors collected and arranged the octanol-water partition coefficients (K(ow)), water solubility (S0), and dissolved humic matter (DHM)-water partition coefficients (K(oc)) for 95 organic compounds, and presented the correlations between each physical property. The K(oc) and K(ow) of dioxins estimated were significantly increased while S0 was decreased on increasing the chlorine number. In the presence of DHM, solubility enhancement (Sw/S0, Sw is the actual solubility in the presence of DHM) in highly chlorinated PCDD/F such as HpCDDs and OCDD is higher than that in low chlorinated ones. It means that dioxins abundant wastes (fly ash) should not be codisposed with organic abundant wastes (sewage sludge, food waste or bottom ash, etc.) to minimize the leachability of dioxins.     

Photoconductivity and photovoltaic effect of charge-transfer complex of poly[4-phenyl-2,6-(p-phenoxy) quinoline] and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone

A new polymer containing a heterocyclic quinoline unit in the main chain, poly[4-phenyl-2,6-(p-phenoxy) quinoline] (PQ), was synthesized by an acid-catalyzed self-condensation reaction. We have found that PQ, which is generally a good insulator itself, can show photoconductivity when doped with an electron acceptor. From the UV-VIS absorption spectra, we found that PQ can form a charge-transfer (CT) complex with an electron acceptor, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The CT complex of the PQ-DDQ mixture showed distinct photoconductivity. Employing the DDQ composition ranging from 5 to 10 wt %, the ratio of dark and photoconductivity was calculated to be about 1 : 100 at an applied electric field of 10₅ V/cm. Additionally, the bilayer sample of PQ/DDQ exhibited a significant photovoltaic effect. The photovoltaic current increased with increasing photointensity. The open-circuit voltage was measured ranging from 0.4 to 0.7 V and the photovoltaic conversion efficiency was calculated to be 10^?3?10_?2%. The PQ film treated with DDQ vapor showed a relatively higher photovoltaic effect than that of the sample treated with DDQ solution. © 1993 John Wiley & Sons, Inc.     

MobileNurse: hand-held information system for point of nursing care

Healthcare information travels with patients and clinicians and therefore the need for information to be ubiquitously available is key to reliable patient care and reliable medical systems. We have implemented MobileNurse, a prototype point-of-care system using PDA. MobileNurse has four modules each of which performs: (1) patient information management; (2) medical order check; (3) nursing recording; and (4) nursing care plan. MobileNurse provides easy input interface and various outputs for nursing records. The system consists of PDAs and a mobile support system (MSS) which supports clinical data exchange between PDAs and hospital information system. Two synchronization modules have been developed to keep the patient data consistent between PDAs and MSS. Clinical trials were performed with six volunteered nurses. They tried MobileNurse for 1-day caring-simulated patients. According to the survey after the trials, most of volunteers agreed that MobileNurse is more helpful and convenient than other non-mobile care systems to check medical orders and retrieve the results of recent clinical tests at the bedside. Through the involvement, we found out that ease-to-use interface is the most critical successful factor for mobile patient care systems.     

Computational fluid dynamic analyses of catalytic combustors for 100 kW-class molten carbonate fuel cell

The asymmetric inner structure of a catalytic combustor causes wall cracking because of regional overheating. Thus, a symmetric shape is proposed in the present work and analyses of the computational fluid dynamics of the existing combustor and the proposed type have been performed. A simulation of the revised combustor without a swirl device revealed that the flow of gases is concentrated on the center of the combustor and only catalysts around the center are used. In the revised combustor with a swirl device, the overall temperatures were estimated to be uniform. However, near the swirl device, high temperature exceeding 1,700 K was measured. Therefore, a heatproof surface coating on the swirl device is necessary for protection of the material. At the initial start-up of the catalytic combustor, hydrogen and natural gas are used. When only natural gas is used, the simulation indicated that the gas does not burn in the revised combustor without a swirl device. However, in the combustor with the swirl device, methane of 34.8% volume burns in the simulation. On the other hand, when hydrogen and natural gas are burned together, methane of 91.7% volume burns in the simulation.     

The use of metal filled via holes for improving isolation in LTCCRF and wireless multichip packages

LTCC MCM's for RF and wireless systems often use metal filled via holes to improve isolation between the stripline and microstrip interconnects. In this paper, results from a 3D-FEM electromagnetic characterization of microstrip and stripline interconnects with metal filled via fences for isolation are presented. It is shown that placement of a via hole fence closer than three times the substrate height to the transmission lines increases radiation and coupling. Radiation loss and reflections are increased when a short via fence is used in areas suspected of having high radiation. Also, via posts should not be separated by more than three times the substrate height for low radiation loss, coupling, and suppression of higher order modes in a package     

Power Allocation and Transmission Period Selection for Device-to-Device Communication as an Underlay to Cellular Networks

Efficient design of device-to-device (D2D) communication calls for D2D users to propose adaptive power allocation strategy and to establish reliable communication links while protecting the QoS of cellular communications. In this paper, we consider the D2D communication as an underlay to relay-assisted cellular networks. To maximize the ergodic capacity, we derive an optimal transmission power under an average power constraint. With the derived optimal transmission power, a transmission period selection strategy for D2D communication is firstly introduced to improve reliability. We derive the outage probability in closed forms and evaluate the ergodic capacity to show performances of the proposed system. Numerical results show that the D2D system can achieve high capacity gains by flexibly allocating transmission power based on channel state information and significantly enhance reliability by selecting a transmission period, while satisfying various QoS conditions for cellular communication.     

Artificial landmark-based underwater localization for AUVs using weighted template matching

This paper deals with vision-based localization techniques in structured underwater environments. For underwater robots, accurate localization is necessary to perform complex missions successfully, but few sensors are available for accurate localization in the underwater environment. Among the available sensors, cameras are very useful for performing short-range tasks despite harsh underwater conditions including low visibility, noise, and large areas of featureless scene. To mitigate these problems, we design artificial landmarks to be utilized with a camera for localization, and propose a novel vision-based object detection technique and apply it to the Monte Carlo localization (MCL) algorithm, a map-based localization technique. In the image processing step, a novel correlation coefficient using a weighted sum, multiple-template-based object selection, and color-based image segmentation methods are proposed to improve the conventional approach. In the localization step, to apply the landmark detection results to MCL, dead-reckoning information and landmark detection results are used for prediction and update phases, respectively. The performance of the proposed technique is evaluated by experiments with an underwater robot platform and the results are discussed.