Whale ‘blubber’ as bio-inspired phase change material

In nature, all living things have various features to survive. For example, marine mammals have an adipose tissue system that protects them from harsh conditions in their environment. This tissue also known as “blubber” provides various features to marine mammals. Buoyancy, insulation, protection and energy storage are among the tasks of this tissue. Thermal energy storage systems are regarded as key to sustainable use of renewables to meet increasing global energy demand. Phase Change Materials (PCM) with thermal energy storage properties are commonly used in a wide variety of applications based on melting-freezing principle. PCMs can be inorganic or organics. Fatty acids are examples of organic PCMs. Please download the PDF file for the full content

Using ahp and topsis to evaluate welding processes for manufacturing plain carbon stainless steel storage tank

Purpose: In the plain carbon stainless steel storage tank manufacturing industry, there are many types of welding processes used. When selecting the most appropriate welding process is usually done intuitively by the manufacturer depending on its own pre-experiences or common applications in similar companies. However, this approach has a shortsighted view since it generally ignores many conflicting criteria effecting the suitable welding process selection. To overcome this problem, this study aims to evaluate important criteria and alternative welding processes by using some of multi-criteria decision-making approaches to come up with better manufacturing decisions. Design/methodology/approach: This study uses a combined methodology of Analytical Hierarchy Process (AHP) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). Since both of these techniques require experts’ contributions, a group meeting is held with the experts from academia and industry. Findings: The study identified the important criteria for welding selection process in storage tank manufacturing. With the help of experts in the domain, both weights of decision criteria and ranking of alternative welding processes were determined. Research limitations/implications: Since the techniques used in the study depend on expert’s contribution, the expert knowledge on the welding process is critical. When the expert changes the resulting decision may also change. Therefore, the selection of the expert(s) must be done carefully. Practical implications: The findings of the study are valid for the specific case of the storage tank manufacturing. The study helps manufacturers to understand the framework of welding process selection and make them aware of various techniques (e.g., AHP and TOPSIS). The approach may also be welcomed by other welding applications. Originality/value: The main contribution of the study is mostly on the practical side. To the authors’ best knowledge, this paper is one of few studies investigating the selection of welding process for a plain carbon stainless steel storage tank manufacturing. It may help to increase the attention of researchers on multi-criteria decision-making applications in the welding field. © International OCSCO World Press. All rights reserved. 201

Numerical study of strength mismatch in cross-weld tensile testing

The strength mismatch effect on the deformation behaviour of defect-free cross-weld tensile specimens, where there is a variation in strength along the length of the specimen, was investigated through 2D finite element analysis. A simple bi-material model, which is generally used in current engineering assessments (e.g. R6 “Assessment of the integrity of structures containing defects”) to examine the strength mismatch effect on the deformation and fracture behaviour of a weld which actually includes a heat-affected-zone, could lead to non- conservative or overly conservative predictions. In fusion welded components, one would generally observe that there is a heat-affected zone where the material properties are different from the weld and base material, and there is a continuous gradient of properties between the two. The material properties in HAZ are generally assigned discretely; however, in our multi-material model these properties are successfully assigned continuously by embedding subroutines into finite element model. This multi-material approach was used to examine the effect of strength mismatch on the local and global deformation behavior of fusion welds. It has been found that the bi-material modeling, by ignoring the HAZ, and multi-material discrete HAZ modeling of the cross-weld specimens leads to unrealistically biaxial stresses at the interfaces where there is an abrupt variation of the material properties. However, multi- material continuous HAZ modeling eliminates unrealistic stress biaxiality and enables to examine the local deformation more accurately. It was also found that the global stress-strain behaviour obtained using the bi- material and multi-material modeling is different

Shortcuts in Stochastic Systems and Control of Biophysical Processes

The biochemical reaction networks that regulate living systems are all stochastic to varying degrees. The resulting randomness affects biological outcomes at multiple scales, from the functional states of single proteins in a cell to the evolutionary trajectory of whole populations. Controlling how the distribution of these outcomes changes over time-via external interventions like time-varying concentrations of chemical species-is a complex challenge. In this work, we show how counterdiabatic (CD) driving, first developed to control quantum systems, provides a versatile tool for steering biological processes. We develop a practical graph-theoretic framework for CD driving in discrete-state continuous-time Markov networks. Though CD driving is limited to target trajectories that are instantaneous stationary states, we show how to generalize the approach to allow for nonstationary targets and local control-where only a subset of system states is targeted. The latter is particularly useful for biological implementations where there may be only a small number of available external control knobs, insufficient for global control. We derive simple graphical criteria for when local versus global control is possible. Finally, we illustrate the formalism with global control of a genetic regulatory switch and local control in chaperone-assisted protein folding. The derived control protocols in the chaperone system closely resemble natural control strategies seen in experimental measurements of heat shock response in yeast and E. coli

Electromigration-Induced Propagation of Nonlinear Surface Waves

Due to the effects of surface electromigration, waves can propagate over the free surface of a current-carrying metallic or semiconducting film of thickness h_0. In this paper, waves of finite amplitude, and slow modulations of these waves, are studied. Periodic wave trains of finite amplitude are found, as well as their dispersion relation. If the film material is isotropic, a wave train with wavelength lambda is unstable if lambda/h_0 < 3.9027..., and is otherwise marginally stable. The equation of motion for slow modulations of a finite amplitude, periodic wave train is shown to be the nonlinear Schrodinger equation. As a result, envelope solitons can travel over the film's surface.Comment: 13 pages, 2 figures. To appear in Phys. Rev.

Alloyed Heterostructures of CdSexS1-x Nanoplatelets with Highly Tunable Optical Gain Performance

Here, we designed and synthesized alloyed heterostructures of CdSexS1-x nanoplatelets (NPLs) using CdS coating in the lateral and vertical directions for the achievement of highly tunable optical gain performance. By using homogeneously alloyed CdSexS1-x core NPLs as a seed, we prepared CdSexS1-x/CdS core/crown NPLs, where CdS crown region is extended only in the lateral direction. With the sidewall passivation around inner CdSexS1-x cores, we achieved enhanced photoluminescence quantum yield (PL-QY) (reaching 60%), together with increased absorption cross-section and improved stability without changing the emission spectrum of CdSexS1-x alloyed core NPLs. In addition, we further extended the spectral tunability of these solution-processed NPLs with the synthesis of CdSexS1-x/CdS core/shell NPLs. Depending on the sulfur composition of the CdSexS1-x core and thickness of the CdS shell, CdSexS1-x/CdS core/shell NPLs possessed highly tunable emission characteristics within the spectral range of 560-650 nm. Finally, we studied the optical gain performances of different heterostructures of CdSexS1-x alloyed NPLs offering great advantages, including reduced reabsorption and spectrally tunable optical gain range. Despite their decreased PL-QY and reduced absorption cross-section upon increasing the sulfur composition, CdSexS1-x based NPLs exhibit highly tunable amplified spontaneous emission performance together with low gain thresholds down to ∼53 μJ/cm2. © 2017 American Chemical Society

Platelet-in-Box Colloidal Quantum Wells: CdSe/CdS@CdS Core/Crown@Shell Heteronanoplatelets

Here, the CdSe/CdS@CdS core/crown@shell heterostructured nanoplatelets (NPLs) resembling a platelet-in-box structure are developed and successfully synthesized. It is found that the core/crown@shell NPLs exhibit consistently substantially improved photoluminescence quantum yield compared to the core@shell NPLs regardless of their CdSe-core size, CdS-crown size, and CdS-shell thickness. This enhancement in quantum yield is attributed to the passivation of trap sites resulting from the critical peripheral growth with laterally extending CdS-crown layer before the vertical shell growth. This is also verified with the disappearance of the fast nonradiative decay component in the core/crown NPLs from the time-resolved fluorescence spectroscopy. When compared to the core@shell NPLs, the core/crown@shell NPLs exhibit relatively symmetric emission behavior, accompanied with suppressed lifetime broadening at cryogenic temperatures, further suggesting the suppression of trap sites. Moreover, constructing both the CdS-crown and CdS-shell regions, significantly enhanced absorption cross-section is achieved. This, together with the suppressed Auger recombination, enables the achievement of the lowest threshold amplified spontaneous emission (≈20 μJ cm−2) from the core/crown@shell NPLs among all different architectures of NPLs. These findings indicate that carefully heterostructured NPLs will play a critical role in building high-performance colloidal optoelectronic devices, which may even possibly challenge their traditional epitaxially grown thin-film based counterparts. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Electromigration of Single-Layer Clusters

Single-layer atom or vacancy clusters in the presence of electromigration are studied theoretically assuming an isotropic medium. A variety of distinctive behaviors distinguish the response in the three standard limiting cases of periphery diffusion (PD), terrace diffusion (TD), and evaporation-condensation (EC). A general model provides power laws describing the size dependence of the drift velocity in these limits, consistent with established results in the case of PD. The validity of the widely used quasistatic limit is calculated. Atom and vacancy clusters drift in opposite directions in the PD limit but in the same direction otherwise. In absence of PD, linear stability analysis reveals a new type of morphological instability, not leading to island break-down. For strong electromigration, Monte Carlo simulations show that clusters then destabilize into slits, in contrast to splitting in the PD limit. Electromigration affects the diffusion coefficient of the cluster and morphological fluctuations, the latter diverging at the instability threshold. An instrinsic attachment-detachment bias displays the same scaling signature as PD in the drift velocity.Comment: 11 pages, 4 figure