Efficient Generation of Model Bulk Heterojunction Morphologies for Organic Photovoltaic Device Modeling

Kinetic Monte Carlo (KMC) simulations have been previously used to model and understand a wide range of behaviors in bulk heterojunction (BHJ) organic photovoltaic devices, from fundamental mechanisms to full device performance. One particularly unique and valuable aspect of this type of modeling technique is the ability to explicitly implement models for the bicontinuous nanostructured morphology present in these devices. For this purpose, an Ising-based method for creating model BHJ morphologies has become prevalent. However, this technique can be computationally expensive, and a detailed characterization of this method has not yet been published. Here, we perform a thorough characterization of this method and describe how to efficiently generate controlled model BHJ morphologies. We show how the interaction energy affects the tortuosity of the interconnected domains and the resulting charge transport behavior in KMC simulations. We also demonstrate how to dramatically reduce calculation time by several orders of magnitude without detrimentally affecting the resulting morphologies. In the end, we propose standard conditions for generating model morphologies and introduce a new open-source software tool. These developments to the Ising method provide a strong foundation for future simulation and modeling of BHJ organic photovoltaic devices that will lead to a more detailed understanding of the important link between morphological features and device performance.Comment: Main article: 9 pages, 6 figures, Supplementary Information: 6 pages, 6 figure

Multi-State Logging Freeze Detection Passive RFID Tags

In this work the design and measurement of a passive UHF RFID smart tag suitable for monitoring and recording critical temperature violations in cold chain management are presented. The tag uses moving parts to detect and log different temperate states without the requirement for transceivers, memory and batteries. A simple mechanical method is proposed whereby a moving metallic plate is trapped in one of 4 possible positions by specific environmental temperatures whereby inducing a permanent state based change in the passive RFID tag response. The latched product critical temperature violations can be monitored via the read power required to turn on the tag transponder chip which differs in each state

Inclusive Decay Rate for B→Xd+γB \to X_d + \gamma in Next-to-Leading Logarithmic Order and CP Asymmetry in the Standard Model

We compute the decay rate for the CKM-suppressed electromagnetic penguin decay $B \to X_d + \gamma$ (and its charge conjugate) in NLO QCD, including leading power corrections in $1/m_b^2$ and $1/m_c^2$ in the standard model. The average branching ratio of the decay $B \to X_d\gamma$ and its charge conjugate is estimated to be in the range $6.0 \times 10^{-6} \leq \leq 2.6 \times 10^{-5}$, obtained by varying the CKM-Wolfenstein parameters $\rho$ and $\eta$ in the range $-0.1 \leq \rho \leq 0.4$ and $0.2 \leq \eta \leq 0.46$ and taking into account other parametric dependence. In the stated range of the CKM parameters, we find the ratio $R(d\gamma/s\gamma) = <BR(B \to X_d\gamma)>/$ to lie in the range between 0.017 and 0.074. Theoretical uncertainties in this ratio are found to be small. Hence, this ratio is well suited to provide independent constraints on the CKM parameters. The CP-asymmetry in the $B \to X_d \gamma$ decay rates is found to be in the range $(7 - 35)$. Both the decay rates and CP asymmetry are measurable in forthcoming experiments at $B$ factories and possibly at HERA-B.Comment: 17 pages including 7 postscript figures; uses epsfig; The changes w.r.t the previous version are: A comment about the Bremsstrahlung corrections is added as well as a note on the feasibility of the measurement $B -> X_d gamma

Balkan and Mediterranean Candidates for European Union Membership: The Convergence of their Monetary Policy with that of the European Central Bank

We compare the convergence with German monetary policy of the Balkan and Mediterranean country candidates for EU membership with that of countries that have recently joined the EU. Significant linkages exist between German base money stock and that of recent members of the EU; the same holds true for some of the Mediterranean region candidates for EU membership and for Slovenia and Croatia. Among the other Balkan economies and Turkey, the ability to follow the policies of the Bundesbank is nonexistent. Such weak policy coordination suggests the need for strengthening the financial sectors of these countries, for macroeconomic stabilization and for a period in which they tie their policies more closely to the ECB before they can be considered serious candidates for EU membership.http://deepblue.lib.umich.edu/bitstream/2027.42/39840/3/wp456.pd

The census of complex organic molecules in the solar type protostar IRAS16293-2422

Complex Organic Molecules (COMs) are considered crucial molecules, since they are connected with organic chemistry, at the basis of the terrestrial life. More pragmatically, they are molecules in principle difficult to synthetize in the harsh interstellar environments and, therefore, a crucial test for astrochemical models. Current models assume that several COMs are synthesised on the lukewarm grain surfaces ($\gtrsim$30-40 K), and released in the gas phase at dust temperatures $\gtrsim$100 K. However, recent detections of COMs in $\lesssim$20 K gas demonstrate that we still need important pieces to complete the puzzle of the COMs formation. We present here a complete census of the oxygen and nitrogen bearing COMs, previously detected in different ISM regions, towards the solar type protostar IRAS16293-2422. The census was obtained from the millimeter-submillimeter unbiased spectral survey TIMASSS. Six COMs, out of the 29 searched for, were detected: methyl cyanide, ketene, acetaldehyde, formamide, dimethyl ether, and methyl formate. The multifrequency analysis of the last five COMs provides clear evidence that they are present in the cold ($\lesssim$30 K) envelope of IRAS16293-2422, with abundances 0.03-2 $\times 10^{-10}$. Our data do not allow to support the hypothesis that the COMs abundance increases with increasing dust temperature in the cold envelope, as expected if COMs were predominately formed on the lukewarm grain surfaces. Finally, when considering also other ISM sources, we find a strong correlation over five orders of magnitude, between the methyl formate and dimethyl ether and methyl formate and formamide abundances, which may point to a link between these two couples of species, in cold and warm gas

Creep-fatigue crack growth testing and analysis of pre-strained 316H stainless steel

Material pre-straining is known to have significant effects of the mechanical response and crack growth behaviour of steels. In this paper, the influence of material pre-straining on the subsequent creep-fatigue crack growth behaviour of Type 316H stainless steel at 550 °C has been examined by performing tests on compact tension specimens that were extracted from blocks uniformly pre-compressed at room temperature. Creep-fatigue crack growth tests on pre-compressed material were performed at the frequency of 0.01 Hz and R-ratio of 0.1. The crack growth data obtained from these experiments have been correlated with the C* and K fracture mechanics parameters and the results are compared with the existing creep crack growth data on the pre-compressed and as-received material at 550 °C. The results obtained have also been compared with the creep-fatigue data from experiments on weldments where the crack tip was located in the heat affected zone (HAZ). The crack growth behaviour in creep-fatigue tests on pre-compressed material has been found similar to that of HAZ material and are higher than that of the as-received material. Moreover, depending on the loading condition and frequency the crack growth data obtained from creep-fatigue tests on pre-compressed material may be characterized using C* or ΔK fracture mechanics parameters