We propose a new label recognition system for photonic label switching using self-routing of labels. Binary-coded labels in on-off keying format are considered. The system consists of an all-optical demultiplexer (DeMUX) and an address recognition unit (ARU) consisting of tree-structured switches. The system uses self-routing propagation of an indication bit controlled with address bits. The indication bit is placed in advance of the address bits in the label. In DeMUX, all-optical switches in a configuration of Mach-Zehnder interferometer with semiconductor optical amplifiers (SOA-MZI) are controlled by the indication bit pulse to separate each of the label bits. The indication bit pulse is routed to the destination output port corresponding to the code of the address in ARU. It is shown that all the binary number codes can be recognized with this system. The operation principle is verified by numerical simulation using coupled-mode theory and a rate equation. Moreover, the switching crosstalk is also evaluated.

For reducing bit errors on wireless channels, we have proposed the multiroute coding scheme on multiple routes for wireless multihop networks. In this paper, we introduce ARQ to our multiroute coding scheme. In our multiroute coding scheme, a destination node combines and decodes subpackets which are encoded and divided by a source node. Each intermediate node relays a subpacket, that is, only a part of a packet. Therefore, intermediate nodes cannot detect packet errors, and only a destination node can do so after combining and decoding subpackets. We propose an ARQ scheme between a source node and a destination node. We analyze the proposed ARQ scheme and evaluate the system performance.

Mn1-xZnxFe2O4 thin films with various Zn contents, 300 nm in thickness, were synthesized on glass substrates directly by electroless plating in aqueous solution at 90 without a heat treatment. With XRD, SEM, VSM, the crystallographic structure, morphology of the films and the macroscopic magnetic properties were characterized. The Mn-Zn ferrite films have a single phase spinel structure and well-crystallized columnar grains grow perpendicularly to the substrate. The change of the coercivity is not consistent with that of the bulk materials. As the Zn content in the films increases, the value of Hc decreases firstly, and then increases. At x=0.5, the minimum value of Hc is 3.7 kA/m and the value of Ms is 419.6 kA/m. The hyperfine magnetic fields, cation occupations and the distribution of the magnetic moments in film plane were studied by the conversion electron Mossbauer spectroscopy (CEMS).

There are two methods of writing servo signals with high speed in a perpendicular magnetic recording medium by magnetic duplication: bit printing (BP) and edge printing (EP). In this study, the influence of spacing between master and slave media on duplication characteristics in both BP and EP has been investigated by the three-dimensional finite-element method. The results show that the duplication characteristic in each method is deteriorated with a large spacing. Also, the influence of a small spacing is stronger in BP than in EP.

In this letter, we present a blind carrier frequency offset (CFO) estimator by exploiting the subspace-based technique for multicarrier-code division multiple access (MC-CDMA) systems. Relative high accuracy and low-complexity to the CFO estimation can be achieved by rooting a polynomial. Simulation results are provided for illustrating the effectiveness of the proposed blind polynomial rooting estimator.

This letter presents delayed perturbation bounds (DPBs) for receding horizon controls (RHCs) of continuous-time systems. The proposed DPBs are obtained easily by solving convex problems represented by linear matrix inequalities (LMIs). We show, by numerical examples, that the RHCs have larger DPBs than conventional linear quadratic regulators (LQRs).

This paper considers optical transport and packet networks and discusses the constraints and solutions in computation of traffic engineering paths. We categorize the constraints into prunable or non-prunable classes. The former involves a simple metric which can be applied for filtering to determine the path. The latter requires a methodic consideration of more complicated network element attributes. An example of this type of constraints is path loss in which the metric can be evaluated only on a path basis, as opposed to simply applying the metric to the link. Another form of non-prunable constraint requires adaptation and common vector operation. Examples are the switching type adaptation and wavelength continuity, respectively. We provide possible solutions to cases with different classes of constraints and address the problem of path computation in support of traffic engineering in multi-layer networks where a set of constrains are concurrently present. The solutions include the application of channel graph and common vector to support switching type adaptation and label continuity, respectively.

Wireless mesh networks (WMNs) are gaining significant momentum as a promising technology for the next-coming state-of-the-art wireless networking. Among many factors, the performance of WMNs would be largely affected by the properness of the deployed routing protocols and the efficient usage of wireless resources. Routing protocols are required to well capture WMNs' features while wireless channels should be used efficiently in order to accommodate high amount of traffics over the mesh backbone. Recently, a Tree-based Routing (TBR) protocol become a popular state-of-the-art proactive routing protocol and its tree-based broadcasting become an often used technique. Though TBR protocol is well-suited for WMNs' architecture and the skewed nature of traffic toward the root, the protocol in its current form faces issues which has to be addressed. Specifically, when some or all nodes are equipped with multiple radios, to reduce collision and co-channel interference, not only the parent-child relationship but also the sibling relationship need to be constructed by the TBR protocol in the multi-channel WMNs. In this paper, we propose a hybrid tree-based protocol for concurrent routing and channel assignment over WMNs. The protocol makes use of sibling links to mitigate the aforementioned shortcomings of TBR protocol. Moreover, in order to address high backbone traffic, the protocol integrates a receiver-based channel assignment scheme. The protocol efficiently deploys the parent-child topological relationships of nodes to enhance efficiency of broadcast transmissions over receiver-based multi-channel WMNs. Simulation results over NS-2 network simulator reveal that our proposed hybrid tree-based protocol achieves much higher performance than the utilization of the original receiver-based CA and TBR protocol.

The performance of TCP data transmission deteriorates significantly when a TCP connection traverses a heterogeneous network consisting of wired and wireless links. This is mainly because of packet losses caused by the high bit error rate of wireless links. We proposed receiver-based ACK splitting mechanism in [1]. It is a new mechanism to improve the performance of TCP over wired and wireless heterogeneous networks. Our mechanism employs a receiver-based approach, which does not need modifications to be made to the sender TCP or the base station. It uses the ACK-splitting method for increasing the congestion window size quickly in order to restrain the throughput degradation caused by packet losses due to the high bit error rate of wireless links. In this paper, we develop a mathematical analysis method to derive the throughput of a TCP connection, with/without our mechanism, which traverses wired and wireless heterogeneous networks. By using the analysis results, we evaluate the effectiveness of our mechanism in the network where both of packet losses due to network congestion and those caused by the high bit error rate of wireless links take place. Through An evaluation of the proposed method shows that it can give a good estimation of TCP throughput under the mixture networks of wired/wireless links. We also find that the larger the bandwidth of the wireless link is, the more effective our mechanism becomes, therefore, the mechanism's usability will increase in the future as wireless networks become faster.

Ag and Pd electrical contact pairs are separated at constant separating speeds (5, 10 and 20 mm/s) in a DC 42 V/8.4 A resistive circuit. The motion of the breaking arc is observed with a high-speed video camera. For Ag contacts, the motion of the breaking arc becomes stable at a certain critical gap at separating speeds of 10 mm/s and 20 mm/s, and the breaking arc moves extensively at the separating speed of 5 mm/s. For Pd contacts, the breaking arc moves extensively regardless of the separating speed. These results are attributed to the following causes. For Ag contacts, the difference in the motion of arc spots at each separating speed is changed by the difference in the total energy input to the contacts. For Pd contacts, the temperature of the contact surfaces is kept high because of the lower thermal conductivity of Pd than Ag.

Recently, wireless sensor networks have been seen as a key technology for a ubiquitous computing society. In sensor networks, many network technologies have been developed, whose main concern is reduction of power consumption of sensor nodes. Moreover, these conventional approaches assume that a node in a sensor network operate in a finite quantity and initial battery of a node. However, if we use the sensor network in the natural environment, it means that the batteries of nodes must be exchanged to long term operation. From a viewpoint of the environmental sustainability it is also necessary for sensor nodes to be easily collected and replaced. This paper proposes a routing protocol for sensor networks with high node exchangeability in order to realize the continuous long-term operations of sensor networks. In the proposed routing protocol, power consumption of nodes is partially biased and the region is rotated in order to exchange a set of nodes easily. We evaluate the proposed routing protocol comparing with DSR, and a routing protocol where all nodes try to consume the battery equally. We use evaluation metrics biased toward transmitting data, the battery residue of nodes at the exchange time, the transition of operating nodes. The results show that the difference of the battery residue between the largest and the smallest nodes is 88% and node exchangeability improves by restricting the geographical area of exchanging nodes.

A new hybrid model to calculate echoes and ultrasonic fields scattered by flaws is presented. In this model, transmitted fields by a transducer and fields scattered by flaws are calculated using the Rayleigh integral and the FDTD method, respectively. Received echo signals by the transducer are obtained by the inner product of the transmitted fields and the scattered ones at each grid for the FDTD method, and integrating those in a calculation area. Since the calculation area for the FDTD method can be limited around flaws, the calculation time is short and computer memory usage can be reduced. Experiments are done for two types of test object to confirm the validity of the hybrid model. As a result, experimental results are in good agreement with calculated ones.

We propose a novel clustering scheme considering non-uniform correlation distribution derived by experimental environment property. Firstly, we investigate the entropy property of actual environment, and then show that its spatial correlation is not uniformly distributed. Based on this result, we present the clustering strategy which provides the efficient data aggregation. Through the simulation under the non-uniform correlation distribution, we show the advantage of the proposed scheme in terms of the energy consumption property per node and the network lifetime.

This paper discusses the behavior of the second-order modes (Hankel singular values) of linear continuous-time systems under typical frequency transformations, such as lowpass-lowpass, lowpass-highpass, lowpass-bandpass, and lowpass-bandstop transformations. Our main result establishes the fact that the second-order modes are invariant under any of these typical frequency transformations. This means that any transformed system that is generated from a prototype system has the same second-order modes as those of the prototype system. We achieve the derivation of this result by describing the state-space equations and the controllability/observability Gramians of transformed systems.

Excitation of plasmons on the surface of a metal grating placed in planar or conical mounting is investigated in detail. Most of the results of numerical computations are compared with experimental data. When a TM wave illuminates a metal grating, total or partial absorption of incident light occurs at angles of incidence at which the plasmon surface waves are excited. In planar mounting the absorption is generally strong and nearly total absorption is observed. While in conical mounting, it is not so strong as that in the planar mounting case and a considerable amount of incident power is reflected. This, however, is accompanied by enhanced TM-TE mode conversion and the greater part of the reflected wave is in the TE polarization. The reciprocal of the TM-wave efficiency, hence, is a practical measure in finding the angles of incidence at which the plasmons are excited. Because the angles are sensitive functions of the refractive index of a material over the grating surface, this phenomenon can be used as an index sensor.

Electromechanical switching devices such as relays may be surprisingly forgiving to occasional, but temporary, electrical stress beyond specification. Consequently delayed openings due to welded contacts on the order of milliseconds usually have been unnoticed and hence have not been reason for concern. However, as electrical systems of vehicles are getting "smarter" and more and more diagnostic routines are being implemented, even such short delay times may be translated as errors. Pre-conditioning contact surfaces has been explored as a measure to increase the welding resistance and eliminate contact opening delays. The 20-A-class relay investigated has been optimized to break occasional current peaks up to 80 ADC.

In recent years, there have been ever-increasing demands to miniaturize automotive connectors. However, because the contact force decreases as connectors are miniaturized further, fretting corrosion, which is a typical problem occurring with low-force electric contacts, is expected to become a more serious problem in future. This time we developed a new experimental device capable of controlling the contact load, fretting amplitude, fretting frequency, contact part temperature and humidity optionally. In this report, we used the design of experiments method, and quantitatively evaluated the extent of the influence of the expected factor (in terms of load, amplitude, and plating thickness, etc.) on the fretting phenomenon, which occurs in the tin plating of the connector terminal. Moreover, based on SEM examination, we analyzed the surface and cross section of the contact parts when degradation occurs, and considered the mechanism of the degradation.

A hierarchical representation formed by an octree for a volume ray casting is a well-known data structure to skip over transparent regions requiring little preprocessing and storage. However, it accompanies unnecessary comparison and level shift between octants. We propose a new data structure named half-skewed octree, which is an auxiliary octree to support the conventional octree. In preprocessing step, a half-skewed octree selects eight different child octants in each generation step compared with the conventional octree. During rendering, after comparing an octant of the conventional octree with corresponding octant of the half-skewed octree simultaneously at the same level, a ray chooses one of two octants to jump over transparent regions farther away. By this method, we can reduce unnecessary comparison and level shift between octants. Another problem of a conventional octree structure is that it is difficult to determine a distance from the boundary of a transparent octant to opposite boundary. Although we exploit the previously proposed distance template, we cannot expect the acceleration when a ray direction is almost parallel to the octant's boundary. However, our method can solve it without additional operations because a ray selects one octant to leap farther away. As a result, our approach is much faster than the method using conventional octree while preserving image quality and requiring minimal storage.

A press-fit connection is a solderless electrical connection technology, which utilizes the mechanical contact force generated between through-holes on a printed circuit board (PCB) and terminals with a width slightly larger than the through-hole diameter. This technology has been widely noted recently as a measure against the "Lead Free Requirement" of materials comprising electric/electronic devices, especially in the area of automobile connector. For the application of this technology to automobile connectors, we have to take into account the severe requirement, such as (1) the adaptation to wider through-hole diameter tolerance range and (2) the establishment of connection reliability for the various PCB surface treatments. As a result, we have determined the minimum and maximum contact forces satisfying the long term connection reliability and designed the terminal shape, which has been refined the N-shape cross section developed before, by using three dimensional finite element methods (FEM). Furthermore, we have developed a new type of hard tin plating on terminals, thus preventing the scraping-off of tin during the insertion process, that could result in a short-circuit on the PCB, for the Organic Solderability Preservative (OSP) treated PCB. The press-fit connector for the automobile airbag Electronic Control Units (ECUs) we developed has been able to transfer to the mass-production phase successfully from August 2005.

In this paper, we propose a novel highly reliable packet transmission protocol for ad-hoc wireless networks without deciding the route from a source node to a destination node in advance. The proposed protocol uses distributed surrounding nodes as transmitters of the retransmission packet when the transmitted packet contains an error. In this protocol, when a packet is not correctly received at the destination node, the source node and the surrounding nodes that have correctly received the packet simultaneously retransmit the same data packet to the destination node. The transmitting timing is triggered by the control packet transmitted from the source node. These operations are repeated until the packet reaches to the destination node like automatic repeat request (ARQ). Moreover, the retransmitted packet is encoded by one branch of the space time block code (STBC) for improving the performance with the network diversity effect. We call this method as STBC Distributed ARQ scheme. The performance of the proposed scheme is evaluated by the computer simulations.