Another scope test on nonuse value of the Shimanto river, Japan

In Japan, dramatic decrease in population and tax revenues of local areas have made the preservation of precious local environmental resources difficult. Although people who live in urban areas have a general consciousness toward preservation of such resources, the amount they are willing to pay and how this consciousness can be realized remain vague. The aims of this study are to estimate such willingness to pay (WTP), to consider the applicability of the contingent valuation method, and to suggest a funding scheme for conservation. Estimation is focused on the Shimanto river, famous as the last clear stream of Japan. Consideration includes a comparison of non-response rate between questionnaire formats and a test of scope insensitivity. Comparison between the private goods format and the referendum format is noteworthy because most Japanese do not have the experience of participating referendum voting on a specific issue. The test of scope insensitivity shows that mean WTP for water quality improvement of the entirety of the river is significantly larger than that of only part. However, weak sensitivity calls for careful benefit transfer. Finally, the paper examines the significance of WTP from a policy perspective. To actualize the will of residents of urban centers for conservation of local environmental assets, it is necessary to establish an institution that can collect the cost for conservation directly from beneficiaries

Design for product-embedded disassembly pathways

This paper presents a computational method for designing an assembly with multiple built-in disassembly pathways, each of which can be activated to retrieve certain components. It is motivated by the global sales of consumer products whose optimal end-of-life options vary geographically due to local recycling/reuse infrastructures and regulatory requirements. Given the sets of components to be retrieved at each location, the method simultaneously determines the spatial configurations of components and locator features, such that each set of desired components is retrieved via a domino-like self-disassembly" process triggered by the removal of a fastener. A multi-objective generic algorithm is utilized to search for Pareto-optimal designs in terms of the realization of the desired disassembly pathways, the satisfaction of distance specifications among components, the minimization of disassembly cost at each location, and the efficient use of on-component locator features. A case study demonstrates the feasibility of the method.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87258/4/Saitou77.pd

Spin relaxation torque in metallic ferromagnets

Spin relaxation torque ${\cal T}$ in uniform metallic ferromagnets with the spin-orbit interaction arising from random impurities is calculated microscopically. ${\cal T}$ is shown to be written by spatial derivatives of the electric field, but is not always given as a divergence of a torque dipole density. The result is due to the fast dissipation of the orbital angular momentum, and thus a conserving spin current cannot be defined. It is discussed that the $\beta$ term in the spin transfer torque can also be asymmetric

Muon g-2 and LHC phenomenology in the Lμ−LτL_\mu-L_\tau gauge symmetric model

In this paper, we consider phenomenology of a model with an $L_\mu-L_\tau$ gauge symmetry. Since the muon couples to the $L_\mu-L_\tau$ gauge boson (called $Z''$ boson), its contribution to the muon anomalous magnetic moment (muon g-2) can account for the discrepancy between the standard model prediction and the experimental measurements. On the other hand, the $Z''$ boson does not interact with the electron and quarks, and hence there are no strong constraints from collider experiments even if the $Z''$ boson mass is of the order of the electroweak scale. We show an allowed region of a parameter space in the $L_\mu-L_\tau$ symmetric model, taking into account consistency with the electroweak precision measurements as well as the muon g-2. We study the Large Hadron Collider (LHC) phenomenology, and show that the current and future data would probe the interesting parameter space for this model.Comment: 26 pages, 12 figure

Formation of a disc gap induced by a planet: Effect of the deviation from Keplerian disc rotation

The gap formation induced by a giant planet is important in the evolution of the planet and the protoplanetary disc. We examine the gap formation by a planet with a new formulation of one-dimensional viscous discs which takes into account the deviation from Keplerian disc rotation due to the steep gradient of the surface density. This formulation enables us to naturally include the Rayleigh stable condition for the disc rotation. It is found that the derivation from Keplerian disc rotation promotes the radial angular momentum transfer and makes the gap shallower than in the Keplerian case. For deep gaps, this shallowing effect becomes significant due to the Rayleigh condition. In our model, we also take into account the propagation of the density waves excited by the planet, which widens the range of the angular momentum deposition to the disc. The effect of the wave propagation makes the gap wider and shallower than the case with instantaneous wave damping. With these shallowing effects, our one-dimensional gap model is consistent with the recent hydrodynamic simulations.Comment: 15 pages, 13 figures, accepted for publication in MNRA

Diffusive versus local spin currents in dynamic spin pumping systems

Using microscopic theory, we investigate the properties of a spin current driven by magnetization dynamics. In the limit of smooth magnetization texture, the dominant spin current induced by the spin pumping effect is shown to be the diffusive spin current, i.e., the one arising from only a diffusion associated with spin accumulation. That is to say, there is no effective field that locally drives the spin current. We also investigate the conversion mechanism of the pumped spin current into a charge current by spin-orbit interactions, specifically the inverse spin Hall effect. We show that the spin-charge conversion does not always occur and that it depends strongly on the type of spin-orbit interaction. In a Rashba spin-orbit system, the local part of the charge current is proportional to the spin relaxation torque, and the local spin current, which does not arise from the spin accumulation, does not play any role in the conversion. In contrast, the diffusive spin current contributes to the diffusive charge current. Alternatively, for spin-orbit interactions arising from random impurities, the local charge current is proportional to the local spin current that constitutes only a small fraction of the total spin current. Clearly, the dominant spin current (diffusive spin current) is not converted into a charge current. Therefore, the nature of the spin current is fundamentally different depending on its origin and thus the spin transport and the spin-charge conversion behavior need to be discussed together along with spin current generation

Mass Estimates of a Giant Planet in a Protoplanetary Disk from the Gap Structures

A giant planet embedded in a protoplanetary disk forms a gap. An analytic relationship among the gap depth, planet mass $M_{p}$, disk aspect ratio $h_p$, and viscosity $\alpha$ has been found recently, and the gap depth can be written in terms of a single parameter $K= (M_{p}/M_{\ast})^2 h_p^{-5} \alpha^{-1}$. We discuss how observed gap features can be used to constrain the disk and/or planet parameters based on the analytic formula for the gap depth. The constraint on the disk aspect ratio is critical in determining the planet mass so the combination of the observations of the temperature and the image can provide a constraint on the planet mass. We apply the formula for the gap depth to observations of HL~Tau and HD~169142. In the case of HL~Tau, we propose that a planet with $\gtrsim 0.3$ is responsible for the observed gap at $30$~AU from the central star based on the estimate that the gap depth is $\lesssim 1/3$. In the case of HD~169142, the planet mass that causes the gap structure recently found by VLA is $\gtrsim 0.4 M_J$. We also argue that the spiral structure, if observed, can be used to estimate the lower limit of the disk aspect ratio and the planet mass.Comment: 16 pages, 5 figures, accepted for publication in The Astrophysical Journal Letter