Locality sensitive hashing (LSH) is one of the widely-used approaches to approximate nearest neighbor search (ANNS) in high-dimensional spaces. The first work on LSH for the Euclidean distance, E2LSH, showed how ANNS can be solved efficiently at a sublinear query time in the database size with theoretically-guaranteed accuracy, although it required a large hash index size. Since then, several LSH variants having much smaller index sizes have been proposed. Their query time is linear or superlinear, but they have been shown to run effectively faster because they require fewer I/Os when the index is stored on hard disk drives and because they also permit in-memory execution with modern DRAM capacity. In this paper, we show that E2LSH is regaining the advantage in query speed with the advent of modern flash storage devices such as solid-state drives (SSDs). We evaluate E2LSH on a modern single-node computing environment and analyze its computational cost and I/O cost, from which we derive storage performance requirements for its external memory execution. Our analysis indicates that E2LSH on a single consumer-grade SSD can run faster than the state-of-the-art small-index methods executed in-memory. It also indicates that E2LSH with emerging high-performance storage devices and interfaces can approach in-memory E2LSH speeds. We implement a simple adaptation of E2LSH to external memory, E2LSH-on-Storage (E2LSHoS), and evaluate it for practical large datasets of up to one billion objects using different combinations of modern storage devices and interfaces. We demonstrate that our E2LSHoS implementation runs much faster than small-index methods and can approach in-memory E2LSH speeds, and also that its query time scales sublinearly with the database size beyond the index size limit of in-memory E2LSH.

Querying in heterogeneous sensor networks is a challenging research issue due to a variety of real-world queries depending on users' preferences. Examples of queries are weather, nearby restaurants, navigation, etc. Users may ask for a breezy path starting from distinct points to distinct train stations. Sensing data collected from wide areas (city or country level) are needed to provide the real-world search as a service for users. Therefore, another challenge is a collaboration of heterogenous sensor networks because deploying sensors in wide areas is impractical. SensorMap [1] collects sensing data from independent sensor networks by allowing data owners to publish their data on the web. Sensing data from all owners are sent to a centric storage in SensorMap. However, distributed data storage is likely to be an efficient solution comparing to a centric storage in which bottleneck always occurs.

This paper describes a control and a structure of a battery driven bipedal robot, WL-15(Waseda Leg-15), which has a 6-DOF parallel mechanism. WL-15 has been designed as a multi-purpose locomotion of robotic systems. This robot is controlled by the QNX real-time operating system. Using Math Works' SIMULINK and OPAL-RT's RT-LAB executed on Windows NT and QNX target systems, control software and pattern generator are developed. A walking control capable of dealing with various dynamic walking is proposed and tested indoors and outdoors using the WL-15. Dynamic biped walking is realized with the maximum step length of 200 mm, the maximum walking speed of 0.8 s/step and the minimum speed of 1.92 s/step. Also, the WL-15 is confirmed to be able to turn 90 deg in two steps and carry a load of 18 kg.

This paper describes the design of a battery driven bipedal robot, which uses 6-DOF parallel mechanisms for its each leg. We have designed this considering a bipedal robot as the leg module that is sufficient for practical use as a multi-purpose locomotor of the robot system. This robot is applicable to various fields, such as medical, welfare and entertainment. In the design of the robot, we have reduced the weight to the maximum extent, taking advantage of the features of the parallel mechanism where the mechanism rigidity is high. Using the developed bipedal locomotor, dynamic walking with the step time of 0.96 sec/step and the step length of 0.2 m/step was conducted, and the effectiveness of its mechanism was confirmed.