Tax Incentives and Household Portfolios: A Panel Data Analysis

This paper investigates the responsiveness of household portfolios to tax incentives by exploiting a substantial tax reform that altered after-tax returns and cost of debt for a large number of households. An extraordinary panel data set that covers two years before and after the reform is used for the analysis. Our empirical findings suggest that households reshuffle their balance sheets in the case of a partial deductibility phase-out. In particular, heavily taxed, interest-bearing assets are used to pay off mortgage debt. Furthermore, we find that taxes have a significant impact on the structure of household portfolios even after controlling for unobserved heterogeneity.Household portfolios, taxation, panel data, natural experiment

EMC/FDTD/MD simulation of carrier transport and electrodynamics in two-dimensional electron systems

We present the implementation and application of a multiphysics simulation technique to carrier dynamics under electromagnetic excitation in supported two-dimensional electronic systems. The technique combines ensemble Monte Carlo (EMC) for carrier transport with finite-difference time-domain (FDTD) for electrodynamics and molecular dynamics (MD) for short-range Coulomb interactions among particles. We demonstrate the use of this EMC/FDTD/MD technique by calculating the room-temperature dc and ac conductivity of graphene supported on SiO2.Comment: Part of JCEL special issue on Multiscale and Multiphysics Modelin

Theoretical Characterization of the Air-Stable, High-Mobility Dinaphtho[2,3-b:2'3'-f]-thiophene Organic Semiconductor

Recently, an optimum mobility of $8.3 cm^2/(Vs)$ has been measured for single-crystal organic field-effect transistors based on the dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]-thiophene (DNTT) molecule. Here, on the basis of quantum chemistry calculations and molecular dynamics simulations, we investigate the microscopic charge transport parameters of the DNTT molecule and crystal. Our findings confirm that the moderate anisotropy of the hole mobility in DNTT is highly dependent on the presence of in-plane herringbonelike intermolecular interactions with large electronic coupling (transfer integral) values (ca. 0.1 eV). Also, we demonstrate that the π-extended heteroaromatic structure leads to strong electronic coupling interactions among neighboring molecules and to a decrease of the intramolecular reorganization energy. In DNTT, thermal modulations of the electronic couplings at 300 K remain small when compared to those exhibited by the pentacene single crystal. This theoretical study suggests that heteroacenes are a promising route toward high-mobility organic semiconductor materials. Charge transport is discussed in the framework of both band and hopping models.Chemistry and Chemical Biolog

Magnetic confinement of the solar tachocline

We study the physics of the solar tachocline and related MHD instabilities. We have performed 3-D MHD simulations of the solar radiative interior to check whether a fossil magnetic field is able to prevent the spread of the tachocline. Starting with a purely poloidal magnetic field and a latitudinal shear meant to be imposed by the convection zone at the top of the radiation zone, we have investigated the interactions between magnetic fields, rotation and shear, using the spectral code ASH on massive parallel supercomputers. In all cases we have explored, the fossil field diffuses outward and ends up connecting with the convection zone, whose differential rotation is then imprinted at latitudes above 40 deg throughout the radiative interior, according to Ferraro's law of isorotation. Rotation remains uniform in the lower latitude region which is contained within closed field lines. We find that the meridional flow cannot stop the inward progression of the differential rotation. Further, we observe the development of non-axisymmetric magnetohydrodynamic instabilities, first due to the initial poloidal configuration of the fossil field, and later to the toroidal field produced by shearing the poloidal field through the differential rotation. We do not find dynamo action as such in the radiative interior, since the mean poloidal field is not regenerated. But the instability persists during the whole evolution, while slowly decaying with the mean poloidal field. According to our numerical simulations, a fossil magnetic field cannot prevent the radiative spread of the tachocline, and thus it is unable to enforce uniform rotation in the radiation zone. Neither can the observed thinness of that layer be invoked as a proof for such an internal fossil magnetic field.Comment: 12 pages, 8 color figures (low res), published in A&A, october 200

Thickness control in a new flexible hybrid incremental sheet forming process

Incremental sheet forming is a cost-effective process for rapid manufacturing of sheet metal products. However, incremental sheet forming also has some limitations such as severe sheet thinning and long processing time. These limitations hamper the forming part quality and production efficiency, thus restricting the incremental sheet forming application in industrial practice. To overcome the problem of sheet thinning, a variety of processes, such as multi-step incremental sheet forming, have been proposed to improve the material flow and thickness distribution. In this work, a new process has been developed by introducing multi-point forming as preforming step before conducting incremental sheet forming processing. Employing an established hybrid sheet forming system and the corresponding thickness prediction model, the preform shape can be optimized by employing a two-step optimization approach to improve the sheet thickness distribution. In total, two case study examples, including a hemisphere part and an aerospace cowling part, are fabricated using the developed hybrid flexible process in this study. The experimental results show that the hybrid flexible forming process with the optimal preform design could achieve sheet parts with more uniform thickness distribution and reduced forming time

Probabilistic Approach to Structural Appraisal of a Building During Construction

Probabilistic assessment methods are very attractive as they allow a systematic treatment of uncertainties.  In this paper, probabilistic models are formulated to predict the reliability of concrete in a structure under construction, a case study of Laboratory Block for College of Continuing Education, University of Port Harcourt, Rivers State.  The safety of the structure is predicted based on the safety index obtained from the probabilistic model.  The design strength of concrete in the structure (grade of concrete) is obtained from schmidt hammer test.  The concrete in the structure gave a safety index value of 2.83 which is less than the target reliability index value of 3.7 for  concrete for safety class 1 BKR[1] and less than the target reliability index of 4.5 for slabs, 4.9 for beams in flexure, 3.6 for beams in shear and 3.9 for columns under dead and live-load combination[2] proving that the structure is not safe and is prone to risk of serious injury to persons and damage to properties

Geochemical investigations of a Portion Obu Hill Marble Deposit Okpella, Edo-State, Nigeria

The Obhu marble deposit is located at latitude 7o 21´ 31.2´´ to 7o 21´ 34.9´´ and longitude 6o 25´ 11.6´´ to 6o 25´ 18.0´´. The geochemical investigations of a portion of the Obhu hill marble deposit was aimed at investigating the reserve estimate in tonnage, rock mass/overburden volume and the geochemical composition of the deposit. This study was conducted by using vertical electrical sounding (VES) geophysical method to obtain the geo-electric parameters of the deposit, and to determine the reserve estimate of the Marble deposit of study area. The result shows that the reserve tonnage is 4.6 x 106 Tons and rock mass reserve/overburden volume ratio is 9:1.The chemical analysis were compared with the RMRDC of Nigeria for each element suitable for production of cement, fertilizer, iron, steel and other industrial uses. The MgO values of the samples 1 and 2 does not falls within the acceptable value of 6 % of RMRDC, with the exception of sample 3 which falls within the acceptable limit. CaO, Al2O3 and P2O5 values of the samples falls within the acceptable limits of RMRDC and so suggest that the marble can be put to industrial use, while the Fe2O3 content of sample 2 and 3 makes them probably not best suited for industrial use, except for sample 1 having a lower value of 1.85 %. The silica SiO2 content values for the three samples exceeded the recommended standard of RMRDC of 5 %. This result reveals that the marble deposit is suitable for most industrial use