Effects of pressure impulse and peak pressure of a shockwave on microjet velocity in a microchannel

We experimentally investigate the effect of a shockwave on the velocity of a microjet and underwater cavitation onset in a microchannel, focusing on the pressure impulse and peak pressure of the shockwave. The pressure impulse and peak pressure of the shockwave are separately varied by using non-spherical laser-induced shockwaves (Tagawa et al. in J Fluid Mech 808:5–18, 2016). We conduct two kinds of experiments. In one experiment, we install a narrow tube and a hydrophone in different configurations in large water-filled tank. We measure the shockwave pressure and the jet velocity simultaneously in order to elucidate the effects of pressure profile of shockwaves on the jet velocity. In the other experiment, we record the jet formation and cavitation onset to investigate the effect of cavitation onset on the jet velocity in an L-shaped microchannel. The experimental results suggest that the jet velocity depends only on the pressure impulse of the shockwave, while the probability of cavitation onset depends only on the peak pressure of the shockwave. The above findings provide new insights for advancing a control method for high-speed microjets.     

Impact of Bi Deficiencies on Ferroelectric Resistive Switching Characteristics Observed at p‐Type Schottky‐Like Pt/Bi1–δFeO3 Interfaces

This work reports a resistive switching effect observed at rectifying Pt/Bi_1–δFeO₃ interfaces and the impact of Bi deficiencies on its characteristics. Since Bi deficiencies provide hole carriers in BiFeO₃, Bi‐deficient Bi_1–δFeO₃ films act as a p‐type semiconductor. As the Bi deficiency increased, a leakage current at Pt/Bi_1–δFeO₃ interfaces tended to increase, and finally, rectifying and hysteretic current–voltage (I–V) characteristics were observed. In I–V characteristics measured at a voltage‐sweep frequency of 1 kHz, positive and negative current peaks originating from ferroelectric displacement current were observed under forward and reverse bias prior to set and reset switching processes, respectively, suggesting that polarization reversal is involved in the resistive switching effect. The resistive switching measurements in a pulse‐voltage mode revealed that the switching speed and switching ratio can be improved by controlling the Bi deficiency. The resistive switching devices showed endurance of >10⁵ cycles and data retention of >10⁵ s at room temperature. Moreover, unlike conventional resistive switching devices made of metal oxides, no forming process is needed to obtain a stable resistive switching effect in the ferroelectric resistive switching devices. These results demonstrate promising prospects for application of the ferroelectric resistive switching effect at Pt/Bi_1–δFeO₃ interfaces to nonvolatile memory.     

On the buckling and collapse of moderately thick composite cylinders under hydrostatic pressure

This paper presents a summary of the work carried out at Washington University in recent years on the buckling and associated non-linear response and collapse of moderately thick composite cylindrical shells. Ring elements in conjunction with a three-dimensional elasticity formulation are employed in the analysis. The buckling and postbuckling imperfection sensitivity in individual modes is studied first. The problem of interaction between local and overall instabilities is then investigated in detail. Imperfection sensitivity of typical ring-stiffened shells is established by using a simple and effective approach that combines the asymptotic procedure and the amplitude modulation technique. The influence of dynamic application of the hydrostatic pressure is investigated with the simplified model. The results obtained are compared with those produced by a two-dimensional program package which includes full-fledged non-linear analysis with ring elements, and commercial programs wherever possible. The study has thrown light on several issues regarding the modeling and behavioral aspects of thick composite shells which are summarized at the conclusion of the paper.     

Latent structure modeling underlying theophylline tablet formulations using a Bayesian network based on a self-organizing map clustering

The “quality by design” concept in pharmaceutical formulation development requires the establishment of a science-based rationale and design space. In this article, we integrate thin-plate spline (TPS) interpolation, Kohonen’s self-organizing map (SOM) and a Bayesian network (BN) to visualize the latent structure underlying causal factors and pharmaceutical responses. As a model pharmaceutical product, theophylline tablets were prepared using a standard formulation. We measured the tensile strength and disintegration time as response variables and the compressibility, cohesion and dispersibility of the pretableting blend as latent variables. We predicted these variables quantitatively using nonlinear TPS, generated a large amount of data on pretableting blends and tablets and clustered these data into several clusters using a SOM. Our results show that we are able to predict the experimental values of the latent and response variables with a high degree of accuracy and are able to classify the tablet data into several distinct clusters. In addition, to visualize the latent structure between the causal and latent factors and the response variables, we applied a BN method to the SOM clustering results. We found that despite having inserted latent variables between the causal factors and response variables, their relation is equivalent to the results for the SOM clustering, and thus we are able to explain the underlying latent structure. Consequently, this technique provides a better understanding of the relationships between causal factors and pharmaceutical responses in theophylline tablet formulation.     

AgI-coated silver-clad stainless steel hollow waveguides for infrared lightwave transmission and their applications

We fabricated silver iodide (AgI)-coated silver hollow waveguides to transmit a wide range of infrared (IR) light. Silver-clad stainless steel pipes were used as a supporting pipe. Since this type of metallic hollow waveguide has high mechanical strength and heat resistance, it is suitable as a rigid lightwave probe for various applications such as dental or medical laser treatment, IR spectroscopy, thermal radiometry, and laser processing. Considering these applications, we estimated the hollow waveguides with different thicknesses of the AgI layer. By optimizing the AgI layer thickness according to the wavelength of propagating light, we succeeded in efficiently transmitting Er-YAG and CO(2) laser light. We also studied the optical characteristics of a wide range of incoherent light for IR spectroscopy and radiometry applications using these metallic hollow waveguides as lightwave probes.     

Microscopic quantum coherence in a photosynthetic-light-harvesting antenna

We briefly review the coherent quantum beats observed in recent two-dimensional electronic spectroscopy experiments in a photosynthetic-light-harvesting antenna. We emphasize that the decay of the quantum beats in these experiments is limited by ensemble averaging. The in vivo dynamics of energy transport depends upon the local fluctuations of a single photosynthetic complex during the energy transfer time (a few picoseconds). Recent analyses suggest that it remains possible that the quantum-coherent motion may be robust under individual realizations of the environment-induced fluctuations contrary to intuition obtained from condensed phase spectroscopic measurements and reduced density matrices. This result indicates that the decay of the observed quantum coherence can be understood as ensemble dephasing. We propose a fluorescence-detected single-molecule experiment with phase-locked excitation pulses to investigate the coherent dynamics at the level of a single molecule without hindrance by ensemble averaging. We discuss the advantages and limitations of this method. We report our initial results on bulk fluorescence-detected coherent spectroscopy of the Fenna-Mathews-Olson complex.     

Postbuckling analysis of layered composites using p- version finite strips

This paper presents the results of a study on the buckling and postbuckling analyses of layered shear-deformable composite plates using p-version finite strips. The plates are considered to be sufficiently long so that the effect of boundary conditions along the shorter edges is of little significance; this makes it possible to use the ‘exact’ trigonometric functions in the longitudinal direction. The displacement field in the transverse direction is discretized by p-version finite strips and convergence is studied by p-extension, i.e. keeping the number of strips relatively small whilst increasing the polynomial order till convergence of the buckling load or the postbuckling stiffness is achieved. Detailed convergence studies are presented and comparison with results of earlier investigations are shown wherever appropriate. The results demonstrate the superior convergence characteristics of the p-version approach.     

Prototype learning for structured pattern representation applied to on-line recognition of handwritten Japanese characters

This paper describes prototype learning for structured pattern representation with common subpatterns shared among multiple character prototypes for on-line recognition of handwritten Japanese characters. Prototype learning algorithms have not yet been shown to be useful for structured or hierarchical pattern representation. In this paper, we incorporate cost-free parallel translation to negate the location distributions of subpatterns when they are embedded in character patterns. Moreover, we introduce normalization into a prototype learning algorithm to extract true feature distributions in raw patterns to aggregate distributions of feature points to subpattern prototypes. We show that our proposed method significantly improves structured pattern representation for Japanese on-line character patterns.     

Development of a Time–Intensity Evaluation System for Consumers: Measuring Bitterness and Retronasal Aroma of Coffee Beverages in 106 Untrained Panelists

In order to develop products that are acceptable to consumers, it is necessary to incorporate consumers’ intentions into products’ characteristics. Therefore, investigation of consumers’ perceptions of the taste or smell of common beverages provides information that should be useful in predicting market responses. In this study, we sought to develop a time–intensity evaluation system for consumer panels. Using our system, we performed time–intensity evaluation of flavor attributes (bitterness and retronasal aroma) that consumers perceived after swallowing a coffee beverage. Additionally, we developed quantitative evaluation methods for determining whether consumer panelists can properly perform time–intensity evaluation. In every trial, we fitted an exponential function to measured intensity data for bitterness and retronasal aroma. The correlation coefficients between measured time–intensity data and the fitted exponential curves were greater than 0.8 in about 90% of trials, indicating that we had successfully developed a time–intensity system for use with consumer panelists, even after just a single training trial using a nontrained consumer. We classified participants into two groups based on their consumption of canned coffee beverages. Significant difference was observed in only AUC of sensory modality (bitterness compared with retronasal aroma) among conventional TI parameters using two‐way ANOVA. However, three‐way ANOVA including a time course revealed significant difference between bitterness and retronasal aroma in the high‐consumption group. Moreover, the high‐consumption group more easily discriminated between bitterness and retronasal aroma than the low‐consumption group. This finding implied that manufacturers should select consumer panelists who are suitable for their concepts of new products.