Tracking a Sea Turtle by an AUV with a Multibeam Imaging Sonar: Toward Robotic Observation of Marine Life

International Journal of Control, Automation and Systems - This paper proposes a method for autonomous underwater vehicles to chase sea turtles without attaching any tag to them, toward efficient...     

Experimental study on the hazards of the jet diffusion flame of liquefied dimethyl ether

Dimethyl ether (DME) has been considered as a substitute for diesel fuel because it has a low auto-ignition temperature and produces less NO_x, SO_x, and particulate matter. However, the introduction of DME vehicles needs widely available DME supply stations. Moreover, the preparation of safety regulations for DME supply stations is very important, and so safety data is needed. Therefore, the present paper reports the hazards of the DME jet diffusion flame, which is one of several hazardous properties of DME, by studying the results of leaking gas and liquid DME. DME jets were released horizontally from circular nozzles whose diameters were 0.2, 0.4, 0.8 and 2 mm, and the release pressure was varied from the saturated vapor pressure to 2 MPa. When gaseous DME was released at the saturated vapor pressure, the flame was blown out. However, when liquefied DME was released, the flame formed. We obtained the experimental equations for estimating the scale and thermal hazards of DME diffusion flames.     

Burning velocities and kinetics of H2/NF3/N2, CH4/NF3/N2, and C3H8/NF3/N2 flames

The combustion characteristics and reaction mechanism of mixtures containing nitrogen trifluoride (NF₃) were investigated. Burning velocities for H₂/NF₃/N₂, CH₄/NF₃/N₂, and C₃H₈/NF₃/N₂ flames were determined for the first time at various equivalence ratios and N₂ mole fractions. The burning velocities of the latter two flames were similar and showed peaks at equivalence ratios of ∼1.0, while those of the H₂/NF₃/N₂ flames had the pronounced peak at low equivalence ratios where the formation of the wrinkled flames was observed. A detailed kinetic model was constructed to simulate the laminar burning velocities of H₂/NF₃/N₂ and CH₄/NF₃/N₂ flames. The model accurately reproduced the experimental results. Analyses of the reaction mechanism revealed the major reaction pathways that involve the decomposition of NF₃, the oxidation and chain-fluoridation of H₂ and CH₄, and the formation of N₂.     

Three‐phase voltage control method by single‐phase distributed generators connected to islanded distribution network

We have proposed a concept model of emergency islanded operation by using distributed generators (DGs) such as photovoltaics, electric vehicles, or batteries, which can provide power to customers via undamaged distribution network in order to develop the resilient power system against large disasters, and it is named Islanded Distribution Network (IDN). Since there is no guarantee that the three‐phase generation system is interconnected to the IDN, the single‐phase DGs that are installed in the distribution network may be treated as main generators in the IDN operation. If the IDN has only single‐phase DGs, it is difficult to regulate the three‐phase voltage within the allowable range and to compensate the unbalance voltage. The aim of this study is to develop the method to supply three‐phase balanced voltage by single‐phase generators in the IDN. First, the operating condition of the generators is proposed for the supply of three‐phase balanced voltage in the IDN model by algebra calculation. The control method for three single‐phase generators has been developed by using the conditions obtained from the derivation of the generators conditions.     

Composite power systems reliability evaluation based on demand-side reserve

This paper proposes new demand-side reliability indices and useful computational methods for reliability evaluation of composite power systems. These new indices are based on the active power which can reach each demand spot under generating and transmission network constraints. This conception is defined as “reachable power,” and it leads the reserve margin on each demand spot, which is called as “demand-side reserve.” If the reachable power is insufficient to satisfy the demand, load curtailment is required. In the proposed approach, the conception of the load curtailment area is defined, and the estimate method of load curtailment area is indicated. In case the reachable power exceeds the demand, system reliability is evaluated by the demand-side reserve, and the power system is divided into several reliability zones according to the demand-side reserve levels. Small system examples are used to illustrate principles of the proposed approach, and middle system examples show the effectiveness and practicality.     

A new method for registration-based medical image interpolation

A new technique is presented for interpolating between grey-scale images in a medical data set. Registration between neighboring slices is achieved with a modified control grid interpolation algorithm that selectively accepts displacement field updates in a manner optimized for performance. A cubic interpolator is then applied to pixel intensities correlated by the displacement fields. Special considerations are made for efficiency, interpolation quality, and compression in the implementation of the algorithm. Experimental results show that the new method achieves good quality, while offering dramatic improvement in efficiency relative to the best competing method.     

A new electric power network for effective transportation of small power of dispersed generation plants

This paper proposes a new electric power network that makes it possible for many types of dispersed generation plants owned by nonutility organizations to participate in an electric power market without the disadvantages of existing power utility and customers. This power network is called an open electric energy network (OEEN) because the network is open to the many types of plants for the participation. For achieving such openness, electric power storage devices, load controller at each customer and data communication network are installed in OEEN; the flow of excess electric power generated by each plant is controlled autonomously and in a distributed way. That is, the control is done by transmitting the data on excess electric power such as generation and demand point, power quality, price, etc., from each dispersed generation plant to the power storage devices and the load controllers through the communication network. Since this data-driven power flow control is similar to the mail system for a packet with the addresses of sender and receiver, it is called packet electric power transportation. In OEEN the storage device plays a different role from load leveling. Therefore, the way to determine the storage capacity differs from the conventional approach. In this paper, the applicability of queuing theory for determining the capacity is also discussed.     

Disconnection control of wind power generators for the purpose of reducing frequency fluctuation

This paper proposes a new approach for disconnection control of wind power generators to reduce the frequency fluctuation caused by wind power. The approach is based on the correlation between frequency and total output of wind power generators and the turbulence degrees of individual wind power generators. At a control center, frequency and all the outputs of wind power generators are monitored, and the correlation and the turbulence degrees are computed on‐line. If the large variation of frequency is detected, then whether the variation comes from the wind power generators or loads is checked by using the correlation. When the wind power generators cause the frequency variation, the wind power generator with maximum turbulence degree is searched and disconnected from the power systems. This search and disconnection process is repeated until the correlation reaches the level where the frequency variation observed is not caused by the wind power generators. The effectiveness of the proposed approach was confirmed with the simulation studies of a two‐area interconnected power system including many wind power generators. The results show that the correlation and the turbulence degree are useful for the reduction of frequency fluctuation so as not to disconnect too many wind power generators. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(1): 10–18, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20911