Peer-to-peer complementary currencies can be powerful tools for promoting collaborations and building relationships on the Internet. i-wat is a proposed such currency based on WAT System, a polycentric complementary currency using WAT tickets as its medium of exchange. Participants spontaneously issue and circulate the tickets as needed, whose values are backed up by chains of trust. i-wat implements the tickets electronically by exchanges of messages signed in OpenPGP. This paper clarifies the trust model of i-wat, and investigates how it is related with that of PGP. To implement the model by dynamically building an appropriate web of trust (WOT), we claim that it would suffice if the behaviors of participants satisfy the following three properties: 1. mutual signing by knowing, or any two mutual acquaintances sign the public keys of each other, 2. mutual signing by participation, or the drawer and a user of an i-wat ticket sign the public keys of each other, and3. mutual full trust by participation, or the drawer and a user of an i-wat ticket fully trust each other, and a recipient fully trust the corresponding user of a ticket, in the context of PGP public key signing.Likelihood of satisfaction of these properties is supported by the (dis)incentives imposed by the semantics of i-wat. A reference implementation of i-wat has been developed in the form of a Jabber instant messaging client. We are beginning to put the currency system into practical use.

A peer-to-peer complementary currency can be a powerful tool for promoting exchanges and building relationships on the Internet. iWAT [1] is a proposed such currency based on the WAT System [2], a polycentric complementary currency using WAT tickets as its media of exchange: participants spontaneously issue and circulate the tickets as needed, whose values are backed up by chains of trust. iWAT implements the tickets electronically by exchanging messages signed in OpenPGP [3]. This paper investigates an extension to the design of iWAT to facilitate mutual help among peers in need. In particular, we investigate additional "reduction" tickets whose values are reduced over time. By deferring redemption of such tickets, the participants can contribute to reduce the debts of the issuers, and the issuers help participants by providing exchange media that accelerate spending. This paper describes in detail how incentive-compatibility is achieved by this extended design; we predict that the following properties will hold, which resulted from a game-theoretical analysis.1. Rapid circulation, or a reduction ticket will typically circulate at high speed until its effective value reaches the scheduled minimum, and2. Vanishment equilibrium, or the system will be most stable if the values of tickets are to be reduced down to zero. A reference implementation of iWAT has been developed in the form of a plug-in for an XMPP [4],[5] instant messaging client. We have been putting the currency system into practical use, to which the proposed feature has been added.

A 0.4 µm stacked gate cell for a 64 Mbit flash memory has been developed which has the Symmetrical Side Wall Diffusion Self Aligned (SSW-DSA) structure. Using the proposed SSW-DSA cell with p+ pockets at both the drain and the source, and adequate punchthrough resistance to scale the gate length down to sub-half-micron has been obtained. It is also demonstrated that the channel erasing scheme applying negative bias to the gate, which is adopted for the SSW-DSA cell, shows lower trapped charges after Write/Erase (W/E) cycles evaluated by a charge pumping technique, and results in better endurance an retention characteristics than conventional erasing schemes.