Evaluation of Free-Fall Particle CT Images Using State Transition Matrix

Spatial particle density distribution images in a pipe cross section have been evaluated by means of state transition matrix, which is a parameter indicating the dominant particle density transition patterns among time series images consisting of CT 2-D space and 1-D time. State transition characterizes the transition patterns for positions in a cross section as monotonous transitions, sudden transitions, and extreme value transitions. In a simulation, the real part of the state transition matrix is negative and the imaginary part is zero in the case of monotonous transition. The real part is positive and the imaginary part is zero in the case of extreme value transition. The imaginary part is nonzero in the case of sudden transition. In free-fall particles in a vertical pipe, high, sudden, and extreme value transitions do not occur because the particle flow rate at this position is low, and therefore the probability of collision among particles is also low. High, sudden, and extreme value transitions occur near the pipe center when the particle flow rate is high, because the probability of collision among particles is high.     

A review of the changes in nitrogenous compounds of herbage during ensilage

In this review the major nitrogenous components of herbage have been identified and the effects of both plant and microbial enzyme activity on these components during the ensilage process have been described. In particular, the specific effects of the lactic acid bacteria and clostridia on amino acid degradation and the end products of such microbial activity are summarised. The effect of formaldehyde in preventing proteolysis is also discussed.     

Development of a Structure for Blast Wave Mitigation

The internal structure of a blast containment container has been developed and examined by experiments involving the explosion of a high explosive. A steel pipe was selected as an effective structure for blast mitigation, because it dramatically reduces the blast wave in the radial direction near the explosion source. To also reduce the blast wave in the axial direction, two types of model structures consisting of a steel pipe as the main part were examined by both high‐speed photography and pressure measurements of the blast waves. A 0.34‐scale internal structure was constructed by combining these structures. To induce a powerful mitigation effect, the internal structure was filled with a shock‐absorbing material. The peak pressures of C4 explosions in free air were obtained on the basis of the published blast wave data for TNT explosions in free air using an equivalent weight of 1.37. The peak pressures of the blast waves from the structures for all cases were compared with the blast wave data for C4 explosions in free air to estimate the blast mitigation effect. As a result it was estimated that the internal structure not only eliminates the blast pressure in the radial direction but also reduces the blast wave in the axial direction by 36 %. By combining the effects of the internal structure and the shock‐absorbing material, the structure can reduce the peak pressure by 75 %.     

Modeling of the yoke-magnetization in MFL-testing by finite elements

The yoke-magnetization is very popular in magnetic particle testing of welds. The detectability of a flaw by using this method largely depends on the magnetic flux density passing through a specimen to be examined or on the intensity of magnetic field acting in/on the specimen. In Japan inspectors have to check and confirm the appropriate magnetizing situation of the specimen by using an A-type standard test specimen specified in the standard JIS G 0565-1992. The development of indications by magnetic particles on the standard specimen is influenced by the air gap between the standard specimen and the specimen surface to be examined. Since the height and breadth of an artificial flaw in the standard specimen also influence the leakage of the magnetic flux density from the flaw, the information about the magnetizing situation is complex.In this paper we first identify influences of some factors on the magnetic leakage flux density from an artificial flaw in the standard specimen by using FEM modeling. Since the check with the standard specimen gives not a unique information to the magnetization state we investigate the technique, in which intensity of magnetic field acting on the specimen surface is used to characterize the magnetization. A finite element approach is applied to model the magnetization situation. The effectiveness of the modeling is confirmed by an experiment.     

Simulation of dispersion of agglomerates in gas phase – acceleration field and impact on cylindrical obstacle

The dispersion of agglomerates by acceleration field and impact onto cylindrical obstacles in gas phase was successfully simulated by the three-dimensional modified discrete element method qualitatively. In case of gas-phase acceleration fields, agglomerates are dispersed into much smaller fragments comparing to the dispersion in liquid-phase shear or elongation flows. The microscopic structure of agglomerates much affects the dispersibility of agglomerates and the agglomerates containing particle of single-point contact with other particles are extremely easy to be dispersed. The impact onto obstacles is more effective dispersion mechanism than acceleration fields, since rigid agglomerates, which cannot be dispersed by acceleration fields, can be dispersed at rather low gas velocity. Although when the gas velocity is very low, agglomerates are only deformed and stuck to the obstacle surface. Then the dispersion becomes significant and size of fragments decreases with the increase in gas velocity.     

Simulation of dispersion and collection process of agglomerated particles in collision with fibers using discrete element method

The behavior of agglomerates in collision with fibers was simulated using the three-dimensional modified discrete element method and the influences of several factors on the fraction of collected particles were examined. Furthermore the single fiber collection efficiency for agglomerated particles was also investigated. In the case where gas velocity is quite low, agglomerates are only deformed but barely dispersed and thus collected as a single deformable particle. By contrast above some critical gas velocity, constituent particles are dispersed and at the same time partly collected on fibers. The fraction of collected particles first increases then decreases as the van der Waals attractive force between particle and fiber increases. The reason for the decrease in fraction of collected particles in strong adhesion region is that the smooth deformation of agglomerates along the fiber surface is inhibited by too strong adhesion. It was also suggested that there exists an optimum size ratio between the agglomerate size and fiber radius for the collection fraction. This is also closely related to the deformation of agglomerate along the fiber surface. In case of non-agglomerated particle collision, all the particles entering within the collision region are collected by fiber. By contrast in case of agglomerate collision, the dispersion of agglomerates as well as collection occurs in the same process and all the particles colliding with the fiber are not necessarily collected. Consequently the single fiber collection efficiency considerably decreases comparing to that for non-agglomerated particle collision.     

Surface reaction of β-FeOOH film negative electrode for lithium-ion cells

Electrochemical performance of β-FeOOH thin film has been investigated for a low-cost and environmentally friendly negative electrode with a large capacity. The electrode was found out to give an initial large discharge capacity of 864 mAh g⁻¹ and good cycleability with a constant value around 700 mAh g⁻¹ at subsequent cycles. In the first charge process, one electron change reaction proceeded from the initial rest potential of 3.04-1.65 V vs. Li/Li⁺, resulting in the formation of divalent product FeOOHLi. Further charging caused the surface film formation like solid electrolyte interface (SEI) between 1.65 V and 1.18 V vs. Li/Li⁺ together with the reduction of Fe compound from divalent to partially zero-valent, followed by its film growth from 1.18 V to 0.07 V vs. Li/Li⁺.     

Drop Tower Experiments and Numerical Modeling on the Combustion-Induced Secondary Flow in Standing Acoustic Fields

From the microgravity experiments on single fuel droplet combustion and on spark-ignited premixed flame in acoustic field, that have been done in this decade, secondary flow has been confirmed. The flow occurs only when combustion occurs and always in the direction to the neighboring node of velocity oscillation in standing acoustic field. This flow is thought to be driven by a kind of acoustic radiation force that arises from density non-uniformity due to combustion. According to the hypothesis, the driving force is expected to be very similar to buoyancy, being a volumetric force proportional to density difference. Since the mechanism tells that only the density difference due to combustion is the requirements for the occurrence of the secondary flow, a simpler system is employed for the hypothesis validation. A hot wire in a standing acoustic field gives a local temperature rise and the secondary flow is successfully reproduced. To avoid buoyancy that covers the radiation force, microgravity conditions are used. Through direct- and modeled numerical simulations and with drop tower experiments, the validity of the hypothesis is checked out. As a result, the supposed radiation force is found to be able to explain well the characteristics of the secondary flow. It is found that adding an acoustic radiation force term determined from acoustic parameters into conventional CFD calculation, one can sufficiently reproduce and predicts the behavior of the secondary flow numerically.     

Quantitative modeling for risk assessment of Vibrio parahaemolyticus in bloody clams in southern Thailand

A risk assessment of Vibrio parahaemolyticus in bloody clams (Anadara granosa) consumed in southern Thailand was conducted. This study estimated the prevalence and concentration of pathogenic V. parahaemolyticus in bloody clams at harvest and retail stages; and during this process, methods to detect the total and pathogenic V. parahaemolyticus were investigated. Consumption of bloody clams and cooking efficiency were studied using interviews and onsite observation of consumers. A beta-Poisson dose–response model was used to estimate probability of illness applying estimation methods for the most likely parameter values presented by USFDA. Microbial and behavioral data were analyzed by developing a stochastic model and the simulation gave a mean number of times a person would get ill with V. parahaemolyticus by consuming bloody clams at 5.6 × 10^− 4/person/year. Sensitivity analysis demonstrated the fraction of people who did not boil the clams properly was the primary factor in increasing risk. This study serves as an example of how a microbiological risk assessment with limited data collection and international cooperation leads to valuable local insight.