In this study, we propose a fuzzy decision making method for multiobjective stochastic linear programming problems with variance covariance matrices (MOSLPs), in which the criteria of probability ...maximization and fractile optimization are simultaneously considered. For a probability maximization model for an MOSLP, the decision maker is required to specify permissible objective levels. However, fewer values of permissible objective levels for minimization problems result in fewer values of the corresponding distribution function because of the conflicts between them. Similarly, for a fractile optimization model for an MOSLP, the decision maker is required to specify permissible probability levels. However, due to conflicts between the probability levels and the corresponding objective functions, larger values of permissible probability levels result in larger values of the corresponding objective function for minimization problems. In this study, it is assumed that the decision maker has fuzzy goals not only for permissible objective levels of a probability maximization model but also for permissible probability levels of a fractile optimization model, and such fuzzy goals are quantified by eliciting the corresponding membership functions. On the basis of the fuzzy decision, the satisfactory solution of the decision maker is obtained by applying a convex programming technique.
Pulp fibers were fibrillated uniformly into nano-sized fibers using a grinder with a specially designed set of grinding disks. To investigate the effect of the fibrillation through the grinder on the ...physical properties of the composites, dissolved pulp fibers were subjected to various passes through the grinder, and the resulting fibrillated pulp fibers were used to make fibrillated pulp fibers/acrylic resin composites. Scanning electron microscopy observations showed that at above five passes, the structure of the fibrillated pulp fibers did not change significantly. The light transmittances of the composites were increased to 80% up to five passes through the grinder, and did not change after further passes. However, the tensile test and thermal expansion analysis indicated that a degradation of the fibrillated pulp occurred during the grinding treatment. To evaluate the fiber degradation, the degree of crystallinity and degree of polymerization of cellulose were measured. Both decreased as the number of passes through the grinder increased. In addition, to reduce the thermal expansion of composites, the fibrillated pulp fibers were additionally treated by sulfuric acid. The thermal expansion of composites was decreased, because the amorphous region of cellulose was removed.
We have established a method for the preparation of Pt nanoparticles (NPs) with a series of target mean-diameters (dm) and sharp size-distribution, supported on graphitized carbon black (GCB), ...Pt/GCB, without changing the mean interparticle distances (dPt-Pt), on GCB surfaces. This is achieved by the deposition of additional Pt-skin layer(s) on the NPs surfaces of the core Pt/GCB from its suspending aqueous solution, which contains precise amounts of Pt-complex equivalent to the projected thickness of Pt skin-layer(s), by simple bubbling of hydrogen, where the core Pt/GCB was prepared by the nanocapsule method that is able to provide NPs with highly uniform dispersion on the support with an extremely narrow size distribution. Contrary to the common view, we were able to demonstrate a lack of dependence of the long-term stability on the particle size of Pt NPs (dm<5nm) using test protocols for monitoring the load-change cycling and start/stop operation of polymer electrolyte fuel cells (PEFCs) at 65°C. This finding is evidence that the so-called “particle size effect” on the stability is not intrinsic but avoidable for the NP catalysts, in addition to our previous demonstration of the independence of the initial specific activity upon Pt NPs sizes for the oxygen electroreduction. This deviation from “common-sense,” i.e., the improvement of the activity and stability at Pt NPs by means of the sharp size distribution and their uniform dispersion on the GCB support, becomes extremely important as a guiding principle to develop cathode catalysts for practical PEFCs. The present unique achievement of the durability is probably brought about by the mitigation of nonuniform growth of Pt NPs via Ostwald ripening. This is most likely due to the uniform Pt dissolution/re-deposition among the uniformly sized and distributed nanoparticles.
Display omitted
•Management of both high activity & durability at Pt nanocatalysts for fuel cells.•No particle size effects appear on Pt nanoparticle (NP) activity & durability.•Such properties are confirmed with durability test protocols for fuel cell vehicles.•Uniform NP size & dispersion on supports realize such distinctive properties.•We propose a facile preparation of such catalysts to suppress Ostwald ripening.
In this study, we investigated the catalytic properties of N,N-dimethylformamide (DMF)-stabilized gold nanoclusters (AuNCs) in the reduction of 4-nitrophenol (PNP) to 4-aminophenol by NaBH(4), a well ...known model reaction to be catalyzed by metal surfaces. The DMF-stabilized AuNCs were prepared in DMF by a surfactant-free method. The DMF-stabilized AuNCs showed high catalytic activity even when used in small quantities (∼10(-7) g). The pseudo-first-order rate constant (k(app)) and activation energy were estimated to be 3 × 10(-3) s(-1) and 31 kJ mol(-1), respectively, with 1.0 μM of the gold catalyst at 298 K. The catalytic activity of the DMF-stabilized AuNCs was strongly influenced by the layer of adsorbed DMF on the Au NCs. This layer of adsorbed DMF prohibited the reactants from penetrating to the surface of the AuNCs via the diffusion at the beginning of the reaction, resulting in an induction time (t(0)) before PNP reduction began. Restructuring of the DMF layer (essentially a form of activation) was the key to achieving high catalytic activity. In addition, atomically monodisperse Au(25)(SG)(18)NCs (SG: glutathione) showed higher catalytic activity in the PNP reduction (k(app) = 8 × 10(-3) s(-1)) even with a low catalyst concentration (1.0 μM), and there was no induction time (t(0)) in spite of the strongly binding ligand glutathione. This suggested that the catalytically active surface sites of the Au(25)(SG)(18)NCs were not sterically hindered, possibly because of the unique core-shell-like structure of the NCs. Retaining these open sites on AuNCs may be the key to making the NCs effective catalysts.
The Hayabusa2 spacecraft investigated the small asteroid Ryugu, which has a rubble-pile structure. We describe an impact experiment on Ryugu using Hayabusa2's Small Carry-on Impactor. The impact ...produced an artificial crater with a diameter >10 meters, which has a semicircular shape, an elevated rim, and a central pit. Images of the impact and resulting ejecta were recorded by the Deployable CAMera 3 for >8 minutes, showing the growth of an ejecta curtain (the outer edge of the ejecta) and deposition of ejecta onto the surface. The ejecta curtain was asymmetric and heterogeneous and it never fully detached from the surface. The crater formed in the gravity-dominated regime; in other words, crater growth was limited by gravity not surface strength. We discuss implications for Ryugu's surface age.
The near-Earth asteroid (162173) Ryugu is a 900-m-diameter dark object expected to contain primordial material from the solar nebula. The Mobile Asteroid Surface Scout (MASCOT) landed on Ryugu's ...surface on 3 October 2018. We present images from the MASCOT camera (MASCam) taken during the descent and while on the surface. The surface is covered by decimeter- to meter-sized rocks, with no deposits of fine-grained material. Rocks appear either bright, with smooth faces and sharp edges, or dark, with a cauliflower-like, crumbly surface. Close-up images of a rock of the latter type reveal a dark matrix with small, bright, spectrally different inclusions, implying that it did not experience extensive aqueous alteration. The inclusions appear similar to those in carbonaceous chondrite meteorites.
Hayabusa2
is a sample return mission of JAXA launched on 3 December 2014.
Hayabusa2
is the successor of
Hayabusa
, which returned samples from the asteroid Itokawa to the Earth. Although the design ...of
Hayabusa2
follows that of
Hayabusa
, the former is equipped with some new components. The small carry-on impactor (SCI) is one of those components. The SCI is a compact kinetic impactor designed to remove the asteroid surface regolith locally and create an artificial crater. One of the most important scientific objectives of
Hayabusa2
is to investigate the chemical and physical properties of the internal materials and structures of the target body, asteroid Ryugu.
Hayabusa2
will attempt to observe the resultant crater with some scientific instruments and to get samples from around the crater. High kinetic energy is required to create a meaningful crater, however, the impact system design needs to fit within strict constraints. Complicated functions, such as a guidance and control system, are not permitted. A special type of shaped charge is used for the acceleration of the impactor of the SCI in order to make system simpler. Using this explosion technique makes it possible to accelerate the impactor very quickly and to hit the asteroid without a guidance system. However, the impact operation will be complicated because the explosive is very powerful and it scatters high-speed debris at the detonation. This paper describes an overview of the SCI system, the results of the development testing and an outline of the impact experiment of the
Hayabusa2
mission.
PDF
