Pilot scale autothermal gasification of coconut shell with CO2-O2 mixture

This paper explored the feasibility and benefit of CO₂ utilization as gasifying agent in the autothermal gasification process. The effects of CO₂ injection on reaction temperature and producer gas composition were examined in a pilot scale downdraft gasifier by varying the CO₂/C ratio from 0.6 to 1.6. O₂ was injected at an equivalence ratio of approximately 0.33–0.38 for supplying heat through partial combustion. The results were also compared with those of air gasification. In general, the increase in CO₂ injection resulted in the shift of combustion zone to the downstream of the gasifier. However, compared with that of air gasification, the long and distributed high temperature zones were obtained in CO₂-O₂ gasification with a CO₂/C ratio of 0.6–1.2. The progress of the expected CO₂ to CO conversion can be implied from the relatively insignificant decrease in CO fraction as the CO₂/C ratio increased. The producer gas heating value of CO₂-O₂ gasification was consistently higher than that of air gasification. These results show the potential of CO₂-O₂ gasification for producing high quality producer gas in an efficient manner, and the necessity for more work to deeply imply the observation.     

Self‐Limited Nanocrystallization‐Mediated Activation of Semiconductor Nanocrystal in an Amorphous Solid

The construction of semiconductor nanocrystal (SNC)‐based composites is of fundamental importance for various applications, including telecommunication, lasers, photovoltaics, and spintronics. The major challenges are the intentional insertion of dopants into SNCs for expanding their intrinsic functionalities and the scalable incorporation of activated SNCs into host free of hydroxyl and organic species for stabilizing and integrating their performances. An in situ approach is presented to couple the SNC doping and loading processes through self‐limiting nanocrystallization of glassy phase, enabling one‐step construction of fully transparent Ga₂O₃ SNC–glass nanocomposites. It is shown that the intentional introduction of various cation/anion impurities (e.g., F^?, In³⁺, and Ni²⁺) or their combinations into Ga₂O₃ SNCs can be realized by taking advantage of the viscous glass matrix to enhance the desorption barrier of impurity on the SNC surface and strengthen its tendency to incorporate into the SNC lattice. The composite can be rationally activated to show wavelength‐tunable and broadband luminescence covering the spectral ranges of near ultraviolet, visible, and near‐infrared wavebands. The approach is predicted to be general to other SNC materials for functional modulations and will be promising for scalable fabrication of novel SNC‐based composites.     

Foldout Drawing: A Projective Drawing for Fabric Forming

Foldout Drawing argues for the agency of representation as a form of mediation between materials and design. The project uses full-scale drawings to design fabrication and form simultaneously. It demonstrates that a hybrid projective drawing, operating between notational and geometrical logics, can integrate conceptualization, visualization, and fabrication.     

The True Origin of Ductile Fracture in Aluminum Alloys

It has generally been assumed that metals usually fail as a result of microvoid nucleation induced by particle fracture. Here, we concentrate on high-density micropores filled with hydrogen in aluminum, existence of which has been largely overlooked until quite recently. These micropores exhibit premature growth under external loading, thereby inducing ductile fracture, whereas the particle fracture mechanism operates only incidentally. Conclusive evidence of a micropore mechanism is provided by the observation of an instantaneous release of gas at failure. We can therefore conclude that the growth of micropores dominates ductile fracture. Since the material we used has a standard pore density, we can assume that an identical fracture mechanism operates in other aluminum alloys. This finding suggests that intense heat treatment, which is generally believed to enhance the mechanical properties through homogenization, may have entirely the opposite effect. This revelation will have a major impact on the engineering design of metals.     

Activity of two histidine decarboxylases from Photobacterium phosphoreum at different temperatures, pHs, and NaCl concentrations

The major causative agent of scombroid poisoning is histamine formed by bacterial decarboxylation of histidine. The authors reported previously that histamine was exclusively formed by the psychrotrophic halophilic bacteria Photobacterium phosphoreum in scombroid fish during storage at or below 10 degrees C. Moreover, histamine-forming ability was affected by two histidine decarboxylases: constitutive and inducible enzymes. This article reports the effect of various growth and reaction conditions, such as temperature, pH, and NaCl concentration, on the activity of two histidine decarboxylases that were isolated and separated by gel chromatography from cell-free extracts of P. phosphoreum. The histidine decarboxylase activity of the cell-free extracts was highest in 7 degrees C culture; in 5% NaCl, culture growth was inhibited, and growth was best in the culture grown at pH 6.0. Moreover, percent activity of the constitutive and inducible enzymes was highest for the inducible enzyme in cultures grown at 7 degrees C and pH 7.5 and in 5% NaCl. The temperature and pH dependences of histidine decarboxylase differed between the constitutive and inducible enzymes; that is, the activity of histidine decarboxylases was optimum at 30 degrees C and pH 6.5 for the inducible enzyme and 40 degrees C and pH 6.0 for the constitutive enzyme. The differences in the temperature and pH dependences between the two enzymes extended the activity range of histidine decarboxylase under reaction conditions. On the other hand, histidine decarboxylase activity was optimum in 0% NaCl for the two enzymes. Additionally, the effects of reaction temperature, pH, and NaCl concentration on the constitutive enzyme activity of the cell-free extracts were almost the same as those on the whole histidine decarboxylase activity of the cell-free extracts, suggesting that the constitutive enzyme activity reflected the whole histidine decarboxylase activity.     

Optimum excitation signal for long-range inspection of steel wires by longitudinal waves

Optimization of an excitation signal is proposed for long-range inspection of thin steel wires by ultrasonic waves. Due to its sensitivity to flaws normal to the axial direction, a longitudinal wave is a useful tool for flaw detection of wires. We can launch and detect longitudinal waves at arbitrary positions on the wire by using electromagnetic acoustic transducers. The broadband pulse is suitable for achieving high spatial resolution in locating flaws. However, the dispersion of the longitudinal wave distorts the waveform, and consequently decreases the apparent signal amplitude. If the effect of the dispersion is removed, the signal to noise ratio can be expected to be improved and the high flaw detectability can be obtained. In this study, we suggest using the optimum excitation signal, which has been modified to compensate for the dispersion during the propagation of the assumed path length. It is possible that the flaw, which occupies 10% of the cross-sectional area of the wire, can easily be detected from a distance of 10 m.     

Detection and activity of iodine-131 in brown algae collected in the Japanese coastal areas

Iodine-131 (physical half-life: 8.04 days) was detected in brown algae collected off the Japanese coast. Brown algae have been extensively used as bioindicators for radioiodine because of their ability to accumulate radionuclides in high concentration factors. The maximum measured specific activity of ¹³¹I in brown algae was 0.37 ± 0.010 Bq/kg-wet. Cesium-137 was also detected in all brown algal samples used in this study. There was no correlation between specific activities of ¹³¹I and ¹³⁷Cs in these seaweeds. The specific activity of ¹³⁷Cs ranged from 0.0034 ± 0.00075 to 0.090 ± 0.014 Bq/kg-wet. Low specific activity and minimal variability of ¹³⁷Cs in brown algae indicated that past nuclear weapon tests were the source of ¹³⁷Cs. Although nuclear power stations and nuclear fuel reprocessing plants are known to be pollution sources of ¹³¹I, there was no relationship between the sites where ¹³¹I was detected and the locations of nuclear power facilities. Most of the sites where ¹³¹I was detected were near big cities with large populations. Iodine-131 is frequently used in diagnostic and therapeutic nuclear medicine. On the basis of the results, we suggest that the likely pollution source of ¹³¹I, detected in brown seaweeds, is not nuclear power facilities, but nuclear medicine procedures.     

Optimum budget allocation method for projects with critical risks

In this paper, the authors analyze the trade-off problem between project budgets and critical risks. Project managers face the problem to balance cash flows and risks when preventive risk response plans require additional costs. Mathematical modeling approach is used with a metric called risk-based project value (RPV). RPV is an evaluation of projects calculated with cash flows and risk probabilities of activities that constitute the project network diagram. There exists an optimal solution for the budget allocation problem that maximizes the expected project value. There is a condition where additional budgets can improve the project value. The study result suggests that there should be an integrated process to optimize the budget plan with the risk management plan. Methods are developed to obtain optimum budget allocations for projects with various types of activity networks. Evaluation of the marginal cost sensitivity on the RPV supports project manager's decisions on reallocation of budgets.