This paper presents the KAIST interactive bicycle racing simulator system, which consists of a pair of bicycle simulators. The rider on the racing simulator experiences realistic sensations of motion, while being able to see the other bicycle simulator and having the audio-visual experience of riding in a velodrome or on the KAIST campus. The 2nd bicycle of the racing simulator system consists of a bicycle, a 4-DOF platform, a handlebar and a pedal resistance system to generate motion feelings; a real-time visual simulator a HMD and beam projection system; and a 3D sound system. The system has an integrating control network with an AOIM (Area Of Interest Management) based network structure for multiple simulators.

This paper is concerned with the concurrency control for collaborative virtual environments. In particular, we describe how concurrent actions are coordinated in a multi-user, large-scale 3-D layout system CIAO. In contrast to many existing systems that sacrifice responsiveness in order to maintain consistency, CIAO achieves optimal response and notification time without compromising consistency. The optimal responsiveness is achieved by a new multicast-based, optimistic concurrency control mechanism. Even operations on a group of related objects do not entail any latency for concurrency control. We also present the multi-user interfaces of CIAO that provide some sense of isolation as well as rich awareness.

We establish trade-o s between time complexity and write- and access-contention for solutions to the mutual exclusion problem. The write-contention (accesscontention) of a concurrent program is the number of processes that may be simultaneously enabled to write (access) the same shared variable. Our notion of time complexity distinguishes between local and remote references to shared memory. We show that, for any N-process mutual exclusion algorithm with write-contention w, there exists an execution involving only one process in which that process executes (log w N) remote memory references for entry into its critical section. We further show that among these remote references, ( p log w N) distinct remote variables are accessed. For algorithms with access-contention c, we show that the latter bound can be improved to (log c N). The last two of these results imply that a trade-o between contention and time complexity exists even if coherent caching techniques are employed. Because the execution that establishes these bounds involves only one process, our results show that \\fast mutual exclusion " requires arbitrarily high writecontention. We show that these bounds hold when using any ofavariety of synchronization primitives, including read, write, test-and-set, load-and-store, compare-andswap, and fetch-and-add, and that they can be generalized to apply when using even stronger primitives. Our results can be extended to apply to a class of decision problems that includes the leader-election problem. The time bounds that we establish are the rst of their kind

This paper concerns synchronization under read/write atomicity in shared memory multiprocessors.We present a new algorithm for N-process mutual exclusion that requires only read and write operations and that has 0(log2 IV) time complexity, where "time" is measured by counting remote memory references.The time complexity of this algorithm is better than that of all prior solutions to the mutual exclusion problem that are based upon atomic read and write instructions; in fact, the time complexity of most prior solutions is unbounded.Performance studies are presented that show that our mutual exclusion algorithm exhibits scalable performance under heavy contention.In the second part of the paper, we discuss two extensions of our mutual exclusion algorithm.In the first extension, we modify the algorithm so that in the absence of contention only 0(1) memory references are required.In the second extension, the technique of software combining is introduced for the purpose of increasing concurrency when using the algorithm to implement combinable read-modifywrite operations.