Recently, the sensor network technology attracts a great deal of attention achieving a safe and comfortable ubiquitous society. The sensor networks are already used in environment and disaster monitoring, medical care, logistics and transportation.
This paper aimed to understand the outline of the sensor network technology centering on the wireless sensor network technology.

抄録全体を表示

Network sensing using optical fibers have been briefly reviewed from the view point of in-line fiber optic sensors which can be categorized by how the light in the core becomes to be accessible through physical or chemical influences to glass fibers. The prospective picture is described with regard not only to how the system should be designed but also to what extent the viability can be seen as an indispensable technology aiming at damage monitoring and ubiquitous intelligent service space.

抄録全体を表示

In Wireless Sensor Networks, location estimation of sensor nodes is important. Therefore some location estimation methods have been proposed. Especially, in Wireless Sensor Networks based on IEEE802.15.4, a method using received signal strength (RSS) which can be measured by each sensor node is one of the most practicable methods in the way that new hardware is not needed and it is suitable also for the miniaturization. However this technique has a weak point that it needs to investigate the propagation environment of the sensor field to estimate the location of sensor nodes in advance. This report proposes the method that the decision of the parameter of the propagation environment using only measurements obtained during localization without investigating prior. Evaluation of this method is shown by simulation that it is able to decide the parameter of an extent that doesn't influence the location estimation accuracy without investigating the propagation parameter of the sensor field.

抄録全体を表示

Recently, wireless LAN (WLAN) technology has become a major wireless communication method. The communication bandwidth is increasing and speeds have attained rates exceeding 100 Mbps. Therefore, WLAN technology is regarded as one of the promising communication methods for future networks. In addition, public WLAN connection services can be used in many locations. However, the number of the access points (AP) is insufficient for seamless communication and it cannot be said that users can use the service ubiquitously. An ad-hoc network style connection can be used to expand the coverage area of a public WLAN service. By relaying the user messages among the user nodes, a node can obtain an Internet connection via an AP, even though the node is located outside the AP's direct wireless connection area. Such a coverage area extending technology has many advantages thanks to the feature that no additional infrastructure is required. Therefore, there is a strong demand for this technology as it allows the cost-effective construction of future networks.
When a secure ad-hoc routing protocol is used for message exchange in the WLAN service, the message routes are protected from malicious behavior such as route forging and can be maintained appropriately. To do this, however, a new node that wants to join the WLAN service has to obtain information such as the public key certificate and IP address in order to start secure ad-hoc routing. In other words, an initial setup is required for every network node to join the WLAN service properly. Ordinarily, such information should be assigned from the AP. However, new nodes cannot always contact an AP directly. Therefore, there are problems about information delivery in the initial setup of a network node. These problems originate in the multi hop connection based on the ad-hoc routing protocols.
In order to realize an expanded area WLAN service, in this paper, the authors propose a secure public key certificate and address provision scheme during the initial setup phase on mobile nodes for the service. The proposed scheme also considers the protection of user privacy. Accordingly, none of the user nodes has to reveal their unique and persistent information to other nodes. Instead of using such information, temporary values are sent by an AP to mobile nodes and used for secure ad-hoc routing operations. Therefore, our proposed scheme prevents tracking by malicious parties by avoiding the use of unique information. Moreover, a test bed was also implemented based on the proposal and an evaluation was carried out in order to confirm performance. In addition, the authors describe a countermeasure against denial of service (DoS) attacks based on the approach to privacy protection described in our proposal.

抄録全体を表示

Network based wireless sensing has become an important area of research and various new applications for remote sensing are expected to emerge. One of the promising applications is structural health monitoring of building or civil engineering structure and it often requires vibration measurement. For the vibration measurement via wireless network, time synchronization is indispensable. In this paper, we introduce a newly developed time synchronized wireless sensor network system. The system employs IEEE 802.11 standard based TSF counter and sends the measured data with the counter value. It enables consistency on common clock among different wireless nodes. We describe the accuracy evaluation by simulation studies when the size of nodes increased. The hardware and software specifications of the developed wireless sensing system are shown. The experiments were conducted in a three-street reinforced concrete building and results showed the system performs more than sufficiently.

抄録全体を表示

We have developed an optical fiber network combining communication and sensing using a hetero-core spliced fiber optic sensor inserted into an existing communication line. The measurement uses the Internet infrastructure effectively, and the sensitivity characteristic by wavelength of the measurement was examined. In addition, six binary switch modules and one displacement sensor module using the hetero-core spliced fiber optic sensor were inserted into an actual communication line, and the influence on the communication was examined. The hetero-core spliced fiber optic sensor showed the characteristic of loss only. When the sensor is inserted into the communication line, if the loss can be controlled to within tolerance to the wavelength of 1.31 μm of the communication line, a measurement function can be added to the communication line by a comparatively simple construction method. In addition, we realized a multiple binary switch measurement in real-time basis with tandem connection by simple addressing algorithm. The binary switches can be applied to a home security system to monitor the state of doors opening and closing. We have successfully fabricated and demonstrated the binary switch sensing system with tandem connection consisted of three binary switches using the proposed method.

抄録全体を表示

There have been proposed several dynamic load-balancing methods for web server clusters. In order to realize an effective load-balancing, they have required an almost real-time server load information which could be obtained from an observation of client-server interactions or a frequent polling from the load-balancer (dispatcher) to each server. However the observation provides an indirect server load information and the polling interval produces a time-lag. To overcome that problem, this paper proposes a load-balancing method based on a server load estimation. Under an employment of our method, the load-balancer selects an estimated least-loaded server, and then assigns the arriving request to that server. The estimation is based on a fact that the file transfer delay is proportional to the file size. The fact makes it possible to estimate each server load from the last request assigned time and the file size. From a performance comparison with the previously proposed methods, our method can realize an effective load balancing for web server clusters.

抄録全体を表示

The quality of sleep is evaluated based on the sleep stages judged by R-K method or the manual of American Academy of Sleep Medicine. The brainwaves, eye movements, and chin EMG of sleeping subjects are used for the judgment. These methods above, however, require some electrodes to be attached to the head and the face to obtain the brainwaves, eye movements, and chin EMG, thus making the measurements troublesome to be held on a daily basis. If non-invasive measurements of brainwaves, eye movements, and chin EMG are feasible, or their equivalent data can be estimated through other bio-signals, the monitoring of the quality of daily sleeps, which influences the health condition, will be easy. In this paper, we discuss the appearance rate of delta wave occurrences, which is deeply related with the depth of sleep, can be estimated based on the average amount of mutual information calculated by pulse wave signals and body movements measured non-invasively by the pneumatic method. As a result, the root mean square error between the appearance rate of delta wave occurrences measured with a polysomnography and the estimated delta pulse was 14.93%.

抄録全体を表示

The majority of traditional power supply solutions for prolonged activity of mobile robots have involved work robots returning to a charge station for charging or exchanging batteries. These methods have problems such as the interruption of a task in process and the limitation of robot's activity range. As a new approach to solve these problems, we have developed a battery support system that includes an exclusive robot to deliver fresh batteries. The battery support system is made up of a work robot, a support robot, a battery charge station, and a server PC to manage the entire system. The work robot in the system monitors its own battery power and location continuously while implementing tasks assigned by the server PC. If its battery power falls below a certain threshold, the server PC commands the support robot to help the work robot. After the support robot approaches and docks with the work robot, the two robots exchange batteries using the attached battery exchange mechanism. In the present paper, the details of each mechanisms of the system and the performance of the battery support system integrated with the practical mechanics are described, and experimental results are presented.

抄録全体を表示

In this paper, we present an algorithm for estimating surface normal vectors of object from images using multi-light source photometric stereo method in the presence of highlights and shadows. The conventional three-light photometric stereo can not deal with specularity and shadowing because of its simple assumption of a Lambertian surface and local shading. By high intensity or low intensity values, the specular reflection and shadowing will produce an incorrect surface normal in the traditional photometric stereo. We propose a new strategy to eliminate the effects of specularity and shadowing using an algorithm of majority voting in the multi-light source photometry.

抄録全体を表示

For multi-agent systems such as our society, formation and maintenance of some “norms” are important to keep the system efficient and stable. However, mechanisms that such norm are formed, maintained and collapsed are not clear and very fruitful but difficult open problem. Agent-based simulation is a promising approach to this problem. This paper presents a compact framework of simulation with learning agents in traffic signal system as an example of norm formation. Through the implementation of the framework with Genetic Algorithm and some preliminary experiments, the potential of the framework is shown.

抄録全体を表示

Recently, 3G cellular phone that can take a movie has spread by improving the digital camera function. And, 2Dcode has accurate readout and high operability. And it has spread as an information transmission means. However, the symbol is expanded and complicated when information of 2D codes increases. To solve these, 3D code was proposed. But it need the special equipment for readout, and specializes in the enhancing reality feeling technology. Therefore, it is difficult to apply it to the cellular phone. And so, we propose 3D code that can be recognized by the movie shooting function of the cellular phone. And, score information was encoded. We apply Gray Code to the property of music, and encode it. And the effectiveness was verified.

抄録全体を表示

The garbage emitted from households and industries has constantly increased for the recent years, and its treatment cost has been financially burden to the municipal government. Many municipal governments recommend their households to purchase household garbage processors in order to reduce the volume of garbage transferred to and incinerated at their facilities. Actually, there are 1,535 municipal governments, which subsidize their households to purchase electrical garbage processors and/or containers. These subsidies should be assessed from various points of view such as cost and benefit of municipal governments and households, and also global or local environmental loads. An environmental planning department of a city office sent questionnaires to households to investigate utilizations of subsidized processors and/or containers. An environmental organization of citizen supported the department with designing a questionnaire form and analyzing data collected by the questionnaire. In this paper, the processes of designing the form and analyzing the data are explained, and then the evaluation of the subsidy is presented. The conclusions are as follows: Electrical garbage processors would be beneficial for local environmental problems such as lack of final landfill site. However, the processors would increase the CO₂ emission, unless the electricity consumption can be improved.

抄録全体を表示