Entropy Generation in Computation and the Second Law of Thermodynamics

Landauer discussed the minimum energy necessary for computation and stated that erasure of information is accompanied by heat generation to the amount of kT ln2/bit. Modifying the above statement, we claim that erasure of information is accompanied by entropy generation k ln2/bit. Some new concepts will be introduced in the field of thermodynamics that are implicitly included in our statement. The new concepts that we will introduce are ``partitioned state'', which corresponds to frozen state such as in ice, ``partitioning process'' and ``unifying process''. Developing our statement, i.e., our thermodynamics of computation, we will point out that the so-called ``residual entropy'' does not exist in the partitioned state. We then argue that a partioning process is an entropy decreasing process. Finally we reconsider the second law of thermodynamics especially when computational processes are involved.Comment: 5 pages, 2 figure

Outburst Photometry of the Eclipsing Dwarf Nova GY Cancri

We observed the ROSAT-selected eclipsing dwarf nova GY Cnc (=RX J0909.8+1849) during the 2001 November outburst. We refined the orbital period to be 0.17544251(5) d. The fading portion of the outburst was indistinguishable from those of typical dwarf novae with similar orbital periods. However, the signature of orbital humps (or a hot spot) was far less prominently observed in the orbital light curves and eclipse profiles than in usual dwarf novae with similar orbital periods. The combination of low frequency of outbursts and the apparent lack of slowly rising, long outbursts in GY Cnc is difficult to reconcile within the standard framework of dwarf novae. We suspect that GY Cnc may be the first above-the-gap counterpart of unusual eclipsing dwarf novae HT Cas and IR Com.Comment: 6 pages, 7 figures, to appear in Publ. Astron. Soc. Japa

Detection of Hotspot for Korea Earthquake Data using Echelon Analysis and Seismic Wave Energy

Echelon analysis (Myers et al., 1997) is a method to investigate the phase-structure of spatial data systematically and objectively. This method is also useful to prospect the areas of interest in regional monitoring of a surface variable. The spatial scan statistic (Kulldorff, 1997) is a method of detection and inference for the zones of significantly high or low rates based on the likelihood ratio. These zones are called hotspots. The purpose of this paper is to detect the hotspot area for spatial data using echelon. We perform echelon analysis for Korea earthquake data. We use ESRI’s ArcGIS that is geographical information system (GIS) software to make the meshed areas and get contiguity information of these areas. With this contiguity information on the meshed areas, we detect the hotspot area using echelon analysis and spatial scan statistics. In addition, we compare with the result of analysis based on the total of number of times simply and the seismic wave energy

Entropy Production and Heat Generation in Computational Processes

To make clear several issues relating with the thermodynamics of computations, we perform a simulation of a binary device using a Langevin equation. Based on our numerical results, we consider how to estimate thermodynamic entropy of computational devices. We then argue against the existence of the so-called residual entropy in frozen systems such as ice.Comment: 6 pages, 1 figure

Direct Observation of Sub-picosecond Hole Injection from Lead Halide Perovskite by Differential Transient Transmission Spectroscopy

Efficient charge separation at the interfaces between the perovskite and with the carrier transport layers is crucial for perovskite solar cells to achieve high power conversion efficiency. We systematically investigate the hole injection dynamics from MAPbI$_3$ perovskite to three typical hole transport materials (HTMs) PEDOT:PSS, PTAA and NiO$_x$ by means of pump-probe transmission measurements. We photoexcite only near the MAPbI$_3$/HTM interface or near the back surface, and measure the differential transient transmission between the two excitation configurations to extract the carrier dynamics directly related to the hole injection. The differential transmission signals directly monitor the hole injections to PTAA and PEDOT:PSS being complete within 1 and 2 ps, respectively, and that to NiO$_x$ exhibiting an additional slow process of 40 ps time scale. The obtained injection dynamics are discussed in comparison with the device performance of the solar cells containing the same MAPbI$_3$/HTM interfaces.Comment: 5 pages, 5 figure

Interaction between thermal convection and mean flow in a rotating system with a tilted axis

Thermal convection in a sine-type horizontal shear flow in a rotating system with the rotation axis tilted from the vertical direction is investigated, sweeping three parameters: Taylor number, tilt angle of the rotation axis (i.e. latitude) and Rayleigh number. Nonlinear time evolutions show that there is not only a regime in which roll convections of a herringbone pattern accelerate a mean flow but also a regime in which a large-scale east–west roll convection accelerates the mean flow strongly. The parameter region in which this type of stable steady two-dimensional (2D) roll solution exists is determined by linear stability analyses. Even when the 2D steady solution is not linearly stable, unsteady quasi-periodic solutions oscillating around the steady solution can be found in the nonlinear time evolutions. Finally, a simple mechanism for the acceleration of the mean flow by the large-scale east–west roll convection is described in detail, in which both the tilt of the rotation axis and the sine-type horizontal shear of the flow are important