In this paper we give an algorithm to generates all series-parallel graphs with at most m edges. This algorithm generate each series-parallel graph in constant time on average.

We demonstrated the transmission over 80 km at 10 Gb/s by using the amplifier and electroabsorption-modulator integrated laser diode. Tilt-facet antireflection window is implemented, inside of which a monitor photodiode is monolithically integrated for accurate power regulation. To better control the amplifier-input power and to reduce the feedback of the amplified spontaneous emission, an attenuator is incorporated by means of the inner-window. By amplifying the modulated signal and compensating modulator-chirp by gain-saturation in the amplifier, high power optical transmission is achieved from a device with -10 dB attenuation at total laser and amplifier currents of 200 mA.

In 1998, Tseng and Jan proposed a lightweight interactive user identification protocol based on ID-based cryptography. Recently, Hwang et al. modified their protocol to reduce the responding and waiting time for wireless network applications. In this letter, we show that their scheme is vulnerable to impersonation attacks.

This paper describes 40-Gbit/s operation of 1.55-µm electro-absorption (EA) modulators applicable to compact and low-cost transmitters for very-short-reach (VSR) applications. We start by identifying factors that make a multi-quantum-well (MQW) design suitable for high levels of output power and for uncooled operation. From the basic experimental results, we determine that a valence-band discontinuity ΔEv at around 80 meV is optimal in terms of combining high-output-power operation and a good extinction ratio. We then apply the above findings in an InGaAsP-MQW EA modulator that is monolithically integrated with a distributed feedback (DFB) laser, and thus obtain operation with high output power (+1.2 dBm), a high ER (10.5 dB), and a low power penalty (0.4 dB after transmission over 2.6 km of single-mode-fiber). These results confirm the applicability of our EA modulator/DFB laser to VSR applications. After that, we theoretically demonstrate the superiority in terms of ER characteristics of the InGaAlAs-MQW over the conventional InGaAsP-MQW. InGaAlAs-MQW EA modulators are fabricated and demonstrate, for the first time, 40-Gbit/s operation over a wide temperature range (0 to 85).

Due to the pruning and joining of members, multicast groups are dynamic. Both the topology and the total number of links change during multicast sessions, and the multicast performance, measured in terms of the bandwidth consumption, will change accordingly. In this paper, we investigate the dynamic performance of multicast communication with homogeneous packet loss probability; indeed, we evaluate the effects of the pruning of receivers and of subnets, after which we find the optimal placements of repair servers. A new 3-phase algorithm for adapting the optimal repair server placements to the dynamic changes of network topologies is presented and analyzed.

The recent progress in the field of Ti:Er:LiNbO3 waveguide lasers with emission wavelengths in the range 1530 nm < λ < 1603 nm is reviewed. After a short discussion of the relevant fabrication methods concepts and properties of different types of lasers with grating resonator, acoustooptically tunable Fabry Perot type lasers and new ring laser structures are presented.

In this paper, we propose a new reinforcement learning scheme called CHQ that could efficiently acquire appropriate policies under partially observable Markov decision processes (POMDP) involving probabilistic state transitions, that frequently occurs in multi-agent systems in which each agent independently takes a probabilistic action based on a partial observation of the underlying environment. A key idea of CHQ is to extend the HQ-learning proposed by Wiering et al. in such a way that it could learn the activation order of the MDP subtasks as well as an appropriate policy under each MDP subtask. The goodness of the proposed scheme is experimentally evaluated. The result of experiments implies that it can acquire a deterministic policy with a sufficiently high success rate, even if the given task is POMDP with probabilistic state transitions.

Web browsing task is based on depth-first searching scheme, so that searching relevant information from Web may be very tedious. In this paper, we propose personal browsing assistant system based on user intentions modeling. Before explicitly requested by a user, this system can analyze the prefetched resources from the hyperlinked Webpages and compare them with the estimated user intention, so that it can help him to make a better decision like which Webpage should be requested next. More important problem is the semantic heterogeneity between Web spaces. It makes the understandability of locally annotated resources more difficult. We apply semantic annotation, which is a transcoding procedure with the global ontology. Therefore, each local metadata can be semantically enriched, and efficiently comparable. As testing bed of our experiment, we organized three different online clothes stores whose images are annotated by semantically heterogeneous metadata. We simulated virtual customers navigating these cyberspaces. According to the predefined preferences of customer models, they conducted comparison-shopping. We have shown the reasonability of supporting the Web browsing, and its performance was evaluated as measuring the total size of browsed hyperspace.

Most of commercial websites provide customers with menu-driven navigation and keyword search. However, these inconvenient interfaces increase the number of mouse clicks and decrease customers' interest in surfing the websites. To resolve the problem, we propose an information retrieval assistant using a natural language interface in online sales domains. The information retrieval assistant has a client-server structure; a system connector and a NLP (natural language processing) server. The NLP server performs a linguistic analysis of users' queries with the help of coordinated NLP agents that are based on shallow NLP techniques. After receiving the results of the linguistic analysis from the NLP server, the system connector interacts with outer information provision systems such as conventional information retrieval systems and relational database management systems according to the analysis results. Owing to the client-server structure, we can easily add other information provision systems to the information retrieval assistant with trivial modifications of the NLP server. In addition, the information retrieval assistant guarantees fast responses because it uses shallow NLP techniques. In the preliminary experiment, as compared to the menu-driven system, we found that the information retrieval assistant could reduce the bothersome tasks such as menu selecting and mouse clicking because it provides a convenient natural language interface.

Recent progress and achievements in creating single fundamental mode vertical cavity lasers with the technique of etching a 2-dimensional pattern of photonic crystal holes into the top distributed Bragg reflector are described. A simulation method for the design of single mode lasers is described, along with accuracy and limitations in predicting modal properties in these devices. Progress in improving output power, methods of lowering threshold currents, and small signal modulation of single mode lasers are discussed.

We have implemented a distributed sensor system based on an array of fiber Bragg gratings (FBGs), which can measure up to 1000 points with a single piece of fiber. The system consists of FBGs having the same resonant wavelengths and small reflectivities (0.1 dB), and a wavelength tunable optical time-domain reflectometer (OTDR). To interrogate the distributed grating sensors and to address the event locations simultaneously, we have utilized the tunable OTDR. A thermoelectric temperature controller was used to tune the emission wavelength of the OTDR. The operating temperature of the laser diode was changed. By tuning the pulse wavelength of the OTDR, we could identify the FBGs whose resonant wavelengths were under change within the operating wavelength range of the DFB LD. A novel sensor cable with dry core structure and tensile cable was fabricated to realize significant construction savings at an industrial field and in-door and out-door applications. For experiments, a sensor cable having 52 gratings with 10 m separations was fabricated. To prevent confusion with unexpected signals from the front-panel connector zone of the OTDR, a 1 km buffer cable was installed in front of the OTDR. The proposed system could distinguish and locate the gratings that were under temperature variation from 20 to 70.

Nowadays more people have started using their mobile phone to access information they need from anywhere at anytime. In advanced mobile technology, Location Service allows users to quickly pinpoint their location as well as makes a recommendation to fascinating events. However, users desire more appropriate recommendation services. In other words, the message service should push a message at a proper place in time. In consequence, customers obtain a higher level of satisfaction. In this paper, we propose a framework of time, place, purpose and personal profile based recommendation service. We illustrate scenarios in "push", "pull" and "don't disturb" services, where our DB queries can recommend the relevant message to users. The three factors: time, place and purpose are mutually dependent and the basic rules to analyze the essential data are summarized. We also create algorithms for DB query. We are filtering messages by one important factor: personal profile such as user's preference and degree of preference. Furthermore, we discuss an implementation of the prototype system, including results of experimental evaluation.

In this paper, the previously introduced periodic Fourier transform concept is extended to a two-dimensional case. The relations between the periodic Fourier transform, harmonic series representation and Fourier integral representation are also discussed. As a simple application of the periodic Fourier transform, the scattering of a scalar wave from a finite periodic surface with weight is studied. It is shown that the scattered wave may have an extended Floquet form, which is physically considered as the sum of diffraction beams. By the small perturbation method, the first order solution is given explicitly and the scattering cross section is calculated.

This paper presents a long length discrete Hartley transform (DHT) design with a new hardware efficient distributed arithmetic (DA) approach. The new DA design approach not only explores the constant property of coefficients as the conventional DA, but also exploits its cyclic property. To efficiently apply this approach to long length DHT, we first decompose the long length DHT algorithm to short ones using the prime factor algorithm (PFA), and further reformulate it by using Agarwal-Cooley algorithm such that all the partitioned short DHT still consists of the cyclic property. Besides, we also exploit the scheme of computation sharing on the content of ROM to reduce the hardware cost with the trade-off in slowing down the computing speeds. Comparing with the existing designs shows that the proposed design can reduce the area-delay product from 52% to 91% according to a 0.35 µm CMOS cell library.

Under the assumption that clock can be inputted to each register at an arbitrary timing, the minimum feasible clock period can be determined if delays between registers are given. This minimum feasible clock period might be reduced if delays between some registers are increased by delay insertion. In this paper, we propose a delay insertion algorithm to reduce the minimum clock period. First, the proposed algorithm determines a clock schedule ignoring some constraints. Second, the algorithm inserts delays to recover ignored constraints according to the delay-slack and delay-demand of the obtained clock schedule. We show that the proposed algorithm achieves the minimum clock period by delay insertion if the delay of each element in the circuit is unique. Experiments show that the amount of inserting delay and computational time are smaller than the conventional algorithm.

This paper discusses the least-squares linear filtering and fixed-lag smoothing problems of discrete-time signals from uncertain observations when the random interruptions in the observation process are modelled by a sequence of not necessarily independent Bernoulli variables. It is assumed that the observations are perturbed by white noise and the autocovariance function of the signal is factorizable. Using an innovation approach we obtain the filtering and fixed-lag smoothing recursive algorithms, which do not require the knowledge of the state-space model generating the signal. Besides the observed values, they use only the matrix functions defining the factorizable autocovariance function of the signal, the noise autocovariance function, the marginal probabilities and the (2,2)-element of the conditional probability matrices of the Bernoulli variables. The algorithms are applied to estimate a scalar signal which may be transmitted through one of two channels.

Wireless LANs (Local Area Networks) are currently spreading over diverse places such as hotels and airports, as well as offices and homes. Consequently, they provide convenient and important ways to access the Internet. Another type of communication model, Peer-to-Peer (P2P) communication on the Internet, has also attracted much attention, and P2P over wireless LANs will soon be very common. There are concerns about the capability of wireless stations (STAs) to send a large amount of traffic on an uplink. In this paper, we first clarify some issues that arise in this context by examining the feature of the Access Point(AP). Furthermore, we consider the role of the AP and propose, as a solution, ways of enabling both efficient and fair transmission over both the downlink and uplink. We evaluate the proposed schemes through simulations and show that communications over the uplink and downlink can share the wireless LAN access resource effectively. Furthermore, we show that coordinating our solution with the 802.11e Enhanced Distributed Channel Access (EDCA) can meet the different requirements of various types of traffic.

Optical Burst Switching (OBS) has been developed as an efficient switching technique to exploit the capacity provided by Wavelength Division Multiplexing (WDM) transmission technology for the next generation optical Internet. One critical design issue in OBS is how to provide Quality-of-Service (QoS) on optical networks. In order to provide the service differentiation, we propose in this paper a buffer allocation algorithm to schedule bursts at the edge OBS nodes, a bandwidth allocation algorithm and a Fiber Delay Line (FDL) allocation algorithm to schedule bursts at the core OBS nodes. We also introduce a new burst assembly technique in which the burst is generated either when the sum of the collected packet sizes reaches the maximum threshold or when the burst assembling time reaches the timeout limit. Our simulation results show that the proposed algorithms achieve the controllable burst loss probability for different service classes. The bandwidth allocation algorithm performs very well at the core OBS nodes in terms of the low loss probability.

We present a world model for location-aware and user-aware services in ubiquitous computing environments. It can be dynamically organized like a tree based on geographical containment, such as in a user-room-floor-building hierarchy and each node in the tree can be constructed as an executable software component. The model is unique to existing approaches because it enables location-aware services to be managed without databases, can be managed by multiple computers, and provides a unified view of the locations of not only physical entities and spaces, including users and objects, but also computing devices and services. A prototype implementation of this approach was constructed on a Java-based mobile agent system. This paper presents the rationale, design, implementation, and applications of the prototype system.

Given the bivariate polynomial f(x,y), let φ(y) be a root of f(x,y) = 0 with respect to x, i.e. φ(y) is a function of y such that f(φ(y),y) = 0. If φ(y) is analytic at y = 0, then we have its power series expansion φ(y) = α0 + α1y + α2y2 + + αpyp + .(1)Let φ(p)(y) denote φ(y) truncated at yp, i.e. φ(p)(y) = α0 + α1y + α2y2 + + αpyp.(2) It is well-known that we can compute power series roots φ(p)(y) by Newton's method. In fact, given the initial value φ(0)(y) = α0 C, the following Newton's methodφ(k)(y) φ(k-1)(y) - (mod yk+1) (3) computes φ(k)(y) (1 k) in expression (2) efficiently (applying the above formula for k = 1,2,, we can compute the power series root φ(p)(y) of any degree p). The above formula (3) is referred to as "symbolic Newton's method" in this paper. From this formula (3), we can see that the numerical errors in the coefficients αs (s = 0,1,...,k - 1) directly affect the numerical error in the coefficient αk. This implies that the symbolic Newton's method is numerically unstable, i.e., a numerical error in the coefficient αk accumulates as the index k increases. Moreover, with the symbolic Newton's method, even if we need only one coefficient αk, we must compute all coefficients αs (s = 0,1,,k - 1). Thus, when we require only one high degree coefficient αk, the symbolic Newton's method is numerically unstable and inefficient. In this paper, given the integer k (> 0), we present a new algorithm to compute the coefficient αk of (1). The new algorithm is numerically stable and requires no computation of the coefficients other than αk itself.