Transient Rayleigh-Benard-Marangoni Convection due to Evaporation : a Linear Non-normal Stability Analysis

The convective instability in a plane liquid layer with time-dependent temperature profile is investigated by means of a general method suitable for linear stability analysis of an unsteady basic flow. The method is based on a non-normal approach, and predicts the onset of instability, critical wave number and time. The method is applied to transient Rayleigh-Benard-Marangoni convection due to cooling by evaporation. Numerical results as well as theoretical scalings for the critical parameters as function of the Biot number are presented for the limiting cases of purely buoyancy-driven and purely surface-tension-driven convection. Critical parameters from calculations are in good agreement with those from experiments on drying polymer solutions, where the surface cooling is induced by solvent evaporation.Comment: 31 pages, 8 figure

Standard operating procedures for sweetpotato breeding data management. COP Breeding Data Management SweetGAINS

Current modernization efforts of sweetpotato breeding operations in Africa establish a new mindset. A modern sweetpotato breeding program continuously generates vast amounts of data on which it depends for all decision making throughout the program. Without a proper systematization of efforts, it is likely that significant mistakes can be unwillingly made, which would impact in a negative manner both genetic gains and the adoption of new varieties by smallholders. This document describes standard operating procedures (SOPs) for implementing breeding data workflows to ensure that all necessary breeding data are recorded appropriately and made easily accessible. This document needs to be considered as an alive one, as through its ensuing iterations additional SOPs will be added, and the current ones would be modified to reflect the learnings acquired. The data management SOPs in this volume cover the following key sweetpotato breeding data workflows: phenotyping, crossing, quality assessment, germplasm management, and DNA sample management. A relational database, SPBase (www.sweetpotatobase.org)1, plays a central role as a breeding data management system across workflows. Several other digital tools have been developed to connect to SPBase to facilitate recording and uploading different types of data

Ferromagnetism in (In,Mn)As Diluted Magnetic Semiconductor Thin Films Grown by Metalorganic Vapor Phase Epitaxy

In1-xMnxAs diluted magnetic semiconductor (DMS) thin films have been grown using metalorganic vapor phase epitaxy (MOVPE). Tricarbonyl(methylcyclopentadienyl)manganese was used as the Mn source. Nominally single-phase, epitaxial films were achieved with Mn content as high as x=0.14 using growth temperatures Tg>475 C. For lower growth temperatures and higher Mn concentrations, nanometer scale MnAs precipitates were detected within the In1-xMnxAs matrix. Magnetic properties of the films were investigated using a superconducting quantum interference device (SQUID) magnetometer. Room-temperature ferromagnetic order was observed in a sample with x=0.1. Magnetization measurements indicated a Curie temperature of 333 K and a room-temperature saturation magnetization of 49 emu/cm^3. The remnant magnetization and the coercive field were small, with values of 10 emu/cm^3 and 400 Oe, respectively. A mechanism for this high-temperature ferromagnetism is discussed in light of the recent theory based on the formation of small clusters of a few magnetic atoms.Comment: 5 pages, 5 figures, accepted for publication in JVST

Quantitative Study of Magnetotransport through a (Ga,Mn)As Single Ferromagnetic Domain

We have performed a systematic investigation of the longitudinal and transverse magnetoresistance of a single ferromagnetic domain in (Ga,Mn)As. We find that, by taking into account the intrinsic dependence of the resistivity on the magnetic induction, an excellent agreement between experimental results and theoretical expectations is obtained. Our findings provide a detailed and fully quantitative validation of the theoretical description of magnetotransport through a single ferromagnetic domain. Our analysis furthermore indicates the relevance of magneto-impurity scattering as a mechanism for magnetoresistance in (Ga,Mn)As.Comment: 5 pages, 4 figures; v2: missing references included, figures recompressed to improve readabilit

Transition to turbulence in Hunt's flow in a moderate magnetic field

Pressure-driven magnetohydrodynamic duct flow in a transverse uniform magnetic field is studied by direct numerical simulation. The electric boundary conditions correspond to Hunt's flow with perfectly insulating walls parallel to the magnetic field (sidewalls) and perfectly conducting walls perpendicular to the magnetic field (Hartmann walls). The velocity distribution exhibits strong jets at the sidewalls, which are susceptible to instability even at low Reynolds numbers Re. We explore the onset of time-dependent flow and transition to states with evolved turbulence for a moderate Hartmann number $Ha = 100$ . At low Re time-dependence appears in the form of elongated Ting-Walker vortices at the sidewalls of the duct, which, upon increasing Re, develop into more complex structures with higher energy and then the sidewall jets partially detach from the walls. At high values of Re jet detachments disappear and the flow consists of two turbulent jets and nearly laminar core. It is also demonstrated that, there is a range of Re, where Hunt's flow exhibits a pronounced hysteresis behavior, so that different unsteady states can be observed for the same flow parameters. In this range multiple states may develop and co-exist, depending on the initial conditions

Structural and magnetic properties of the (001) and (111) surfaces of the half-metal NiMnSb

Using the full potential linearised augmented planewave method we study the electronic and magnetic properties of the (001) and (111) surfaces of the half-metallic Heusler alloy NiMnSb from first-principles. We take into account all possible surface terminations including relaxations of these surfaces. Special attention is paid to the spin-polarization at the Fermi level which governs the spin-injection from such a metal into a semiconductor. In general, these surfaces lose the half-metallic character of the bulk NiMnSb, but for the (111) surfaces this loss is more pronounced. Although structural optimization does not change these features qualitatively, specifically for the (111) surfaces relaxations can compensate much of the spin-polarization at the Fermi surface that has been lost upon formation of the surface.Comment: 18 pages, 8 figure

An Exploration of Supplier Decision-Making under Threat

Purpose: The use of threats to force supplier compliance is a common practice in current business affairs. Unfortunately, little is known regarding the supplier’s decision process to comply to or resist such a coercive strategy. The paper aims to develop a more comprehensive view of the decision process used by suppliers when threatened by their customers, as well as discover new phenomena regarding supplier Decision-Making Under Threat (DUT). More specifically, it aims at (1) gaining a better understanding of threats by looking at their patterns and commonalities and (2) identifying which consideration factors are relevant when suppliers evaluate threats. Method: To identify which consideration factors are relevant to suppliers when deciding how to react to threats, the study employed an exploratory approach by interviewing 17 marketing practitioners with experiences in DUT. The in-depth interviews lasted between thirty-five and sixty-five minutes and were transcribed. Descriptive coding and template analysis generated thirty-nine descriptors and nine categories that are deemed important when considering DUT. The authors also evaluated the intensity of each of the consideration factors present in the decision process. Findings: The results reveal that it is possible to categorize threats into three components: Objectives, Penalties and Manifestations. Objectives are what the customer is trying to achieve by using the threat, namely demanding price reductions, appropriating intellectual property, procuring financial statements, receiving a bribe, increasing technical requirements, accessing a cost breakdown, modifying delivery terms, and modifying payment terms. The penalty is what the supplier can expect to happen when refusing to comply, such as losing the customer’s sales. Finally, manifestations describe how the threat is presented by the customer. Study results show that these manifestations may be categorized according to their level of ambiguity, predictability, and candor. The results also reveal that at least five cognitive decision criteria are typically considered during the decision process although at different intensity levels from each participant. These criteria include: Dependence, Cost-Benefit Analysis, Relationship Quality, Relational Norm Violations, and Mimetic Isomorphism. Several interesting discoveries were made. For example, Dependence is both the consideration factor for which most people emphasized its influence on their decision and for which most people said that it had no influence at all. Relational norm violations is unique by being the only criterion for which no participant mentioned that it does not influence their decision. The overwhelming majority of study participants considered more than three criteria during the DUT process. Finally, participants said that they experienced negative emotions such as anger and frustration when exposed to threats albeit most did not recognize that it played a role in their decision. These emotions are however believed to be a factor in reducing the supplier’s willingness to comply. Overall, the study finds that DUT is a complex decision process regarding supplier adaptation, and can be a highly emotional experience with long-lasting effects. Originality/value/contribution: By merging the influence strategy research stream and the supplier adaptation research stream together, the study generates a few original and noteworthy contributions. A better understanding of threats is garnered by breaking them down into three components, which consequently extends our understanding of influence strategies. The study also contributes to a deeper understanding of the supplier’s DUT, a new concept described in the paper, by identifying how decision makers include multiple criteria in their decision process. Very few academic papers have specifically looked into threats as a coercive strategy despite its prevalent use in business environments. Those that did focused on a limited set of criteria when analyzing the decision to adapt. The article expands on these previous studies by proposing five decision criteria, which are often considered collectively by participants when examining adaptation under threat, and emphasizes a factor neglected in previous research, namely the role of emotions

Measurement of Length and Position with Frequency Combs

We show two different absolute distance measurement methods with micrometer accuracy based on frequency combs, and we discuss possible applications. Using a mode- locked laser and MEMS-based tracking optics, we measure the 3D position of a retroreflector within 10 ms and with a 24 μm volumetric accuracy. We also investigate modulator-based combs and show that they enable highly sensitive surface topography measurements with microsecond acquisition times and micrometer precision. Moreover, the potential for photonic integration of frequency comb sources is explored