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This study experimentally and theoretically analyzed the performance of two types of large-scale hollow fiber (HF) forward osmosis (FO) modules for pressure retarded osmosis (PRO). The effects of operating conditions on the module performance of the 5-inch scale HF modules with a cross-wound HF configuration were investigated. A modified analytical model, based on the friction-concentration polarization (FCP) model, which combined the PRO theory with water flux and salt leakage, was proposed for PRO performance estimation. The theoretical results agreed within 9.7% deviation with the experimental results under all conditions. The energy efficiency of the HF PRO module was also theoretically derived. The power generation estimation for the 5-inch membrane module revealed that 10 to 15% of the energy could be recovered from the reverse osmosis seawater desalination process. However, some parts of the membrane could not be used efficiently inside the modules because of the non-optimal dimensions. Therefore, new types of modules, having shorter lengths and larger module diameters, were proposed and provided greater net energy output, as compared with the original module, due to the reduction of both the region where the water was not sufficiently permeated and the pressure drop inside the HF membrane.

Understanding the doping mechanism that involves substantial charge transfer between carbon nanotubes and chemical adsorbent is of critical importance for both basic scientific knowledge and nanodevice applications. Nevertheless, it is difficult to estimate the modification of electronic structures of the doped carbon nanotubes. Here we report measurements of electrochemical potentials of n-doped single-walled carbon nanotubes (SWCNTs) by using photoluminescence (PL) measurement. The change of the measured PL intensity before and after n-type doping was used to extract the electrochemical potential using the Nernst equation. The measured electrochemical potentials of SWCNTs approached the theoretical reduction potential of SWCNTs as the mole concentration of the dopant increased. The doping effect was also confirmed by the change of absorption spectroscopy. The quenching of the PL and absorption intensity was strongly correlated to the standard reduction potential of the dopant and its concentration. This...

The recent increase in the size of energy plants has been supported by the development of manufacturing technology for high purity large forgings for the key components of the plant. To assure the reliability and performance of the large forgings, refining technology to make high purity steels, casting technology for gigantic ingots, forging technology to homogenize the material and consolidate porosity are essential, together with the required heat treatment and machining technologies. To meet these needs, the double degassing method to reduce impurities, multi-pouring methods to cast the gigantic ingots, vacuum carbon deoxidization, the warm forging process and related technologies have been developed and further improved. Furthermore, melting facilities including vacuum induction melting and electro slag re-melting furnaces have been installed. By using these technologies and equipment, large forgings have been manufactured and shipped to customers. These technologies have also been applied to the manufacture of austenitic steel vessel components of the fast breeder reactors and components for fusion experiments.

One of the key issues in the utilization of carbon nanotubes (CNTs) for basic researches as well as their applications is to develop a methodology to solubilize/disperse them in solvents. In this review articles, we first summarize individual solubilization of single-walled carbon nanotubes (SWNTs) in solvents using surfactants, polycylcic aromatic molecules, DNA and condensed polymers. We then describe a novel method determining the electronic states of individually dissolved SWNTs having an own chirality index based on the analysis of Nernst equation. We also introduce our recent approach toward the fabrication of a novel catalyst for fuel cell that works at a nonhumid atmosphere using solubilized CNTs as material.

Increasing attention has been focused on carbon dioxide (CO2) heat pump system where the temperature level is rather low, while the operating pressure is rather high. In this system, the density difference between vapor and liquid becomes rather small, which significantly affects flow patterns. Low surface tension and latent heat also have significant influence on two-phase flow patterns and heat transfer. This paper describes experimental and numerical investigation on flow patterns and heat transfer characteristics of boiling flow CO2 at high pressure in horizontal small-bore tubes ranging from 1.0 mm to 3.0 mm I.D. Even though the density difference is rather small at high pressure, phase stratification takes place, which leads to the intermittent dryout at the upper wall. So far developed discrete bubble model by the authors for vertical flows is modified so as to include horizontal flow mechanisms. The predicted flow patterns with this new model agree on the whole with the experimental observation.

The morphology of the compounds formed by the reactive diffusion between solid Fe and liquid Al was experimentally observed using Fe/ Al diffusion couples. The diffusion couples were prepared by an isothermal bonding technique and then immediately annealed at temperatures of T = 973, 1023 and 1073 K for various times up to t = 2.4 × 10 3 s. At these temperatures, Fe is solid, but Al is liquid. During annealing, a compound region consisting of Fe 2 Al 5 and FeAl 3 is formed at the Fe/Al interface in the diffusion couple and grows towards the Fe solid specimen. However, FeAl 2 and FeAl were not detected clearly. The thickness is much smaller for FeAl 3 than for Fe 2 Al 5 , and thus the compound region is mainly composed of Fe 2 Al 5 . At T = 973-1073 K, FeAl 3 is produced as a rather uniform thin layer. On the other hand, the Fe 2 Al 5 region shows the irregular tongue-like morphology at T = 973-1023 K but the uniform layer morphology at T = 1073 K. The irregularity of the Fe 2 Al 5 region is attributed to the anisotropy for the interdiffusion coefficient of Fe 2 Al 5 . The temperature dependence of the irregularity implies that the anisotropy is large at T = 973-1023 K but small at T = 1073 K. The mean thickness of the compound region is proportional to a power function of the annealing time. Although the activation enthalpy of the proportionality coefficient is evaluated with an Arrhenius equation, the morphology of the Fe 2 Al 5 region varies depending on the annealing temperature. In such a case, the rate-controlling process for the growth of the compound region cannot be readily estimated from the activation enthalpy.

Using Cu/Al diffusion couples initially composed of pure Cu and Al, the reactive diffusion in the binary Cu–Al system was experimentally examined in a previous study. The diffusion couple was isothermally annealed in the temperature range of T ¼ 973{1073 K. Due to annealing, compound layers of the � , � and " phases are formed between the Cu-rich solid (� ) phase and the Al-rich liquid (L) phase, and the L=" interface migrates towards the " phase. At each annealing time, the migration distance of the L=" interface is much greater than the total thickness of the compound layers. Furthermore, there exists the parabolic relationship between the migration distance and the annealing time. This means that the migration of the interface is controlled by the volume diffusion in the L phase. The mathematical model for the interface migration controlled by volume diffusion was used in order to analyze quantitatively the migration rate of the interface. Through the analysis, the interdiffusion coefficient D of the L phase was evaluated to be 1:24 � 10 � 9 , 2:91 � 10 � 9 and 3:62 � 10 � 9 m 2 /s at T ¼ 973, 1023 and 1073 K, respectively. Expressing the temperature dependence of D as D ¼ D0 expð� Q=RTÞ, values of D0 ¼ 1:42 � 10 � 4 m 2 /s and Q ¼ 93:5 kJ/mol were obtained by the least-squares method. According to the analysis, the interdiffusion coefficient is much greater for the L phase than for the solid phases. Consequently, the L=" interface migrates towards the " phase, and the migration rate of the interface is much greater than the overall growth rate of the compound layers. [doi:10.2320/matertrans.47.2480]

The reaction at narrow holes method (RANH method) has been proposed for fabricating fiber reinforced metal (FRM), such as an intermetallic compound fiber / metal matrix composite. This study clarifies a microstructure at a fiber / metal matrix interface of FRM fabricated by using a combination of pure-copper and pure-aluminum in the RANH method. Pure-aluminum fiber was inserted into a narrow hole drilled in the copper matrix. The assembly comprising the pure-aluminum fiber and the pure-copper matrix was heated to a temperature greater than eutectic temperature of the copper-aluminum binary alloy. A molten aluminum reacted with copper to form an annular reacted region consisting of g1 intermetallic compound in a single phase near the edge of the narrow hole. The g1 intermetallic compound has very high hardness on the order of 800-900 HV. The annular reacted region may have a high tensile strength and may work as a reinforcing metal fiber in FRM.

Aqueous dispersions of fullerene C70-filled carbon nanotubes (C70@SWNTs or peapods) and empty single-walled carbon nanotubes (empty SWNTs) were prepared with the aid of trimethyl-(2-oxo-2-pyrene-1-yl-ethyl)-ammonium bromide (1), which is a carbon nanotube solubilizer. This is the first report describing the preparation and characterization of the transparent dispersion/dissolution of the peapods. The UV-vis-near-IR spectra of C70@SWNTs-1 and empty SWNTs-1 were almost identical. We found by means of transmission electron microscopy and atomic force microscopy that the empty SWNTs and C70-peapods form helical nanostructures in the shapes of rings, irregular rings, lassos, handcuffs, catenanes, pseudorotaxanes, and figure-eight structures. The mechanism of the superstructure formation has been discussed in relation to the unique characteristics of stiff polymer chains with the aid of an off-lattice Monte Carlo simulation.

The effect of carbon content on the microstrucures, the tensile strength, creep strength and fracture toughness of 10Cr–5W ferritic steels containing from 0.02 to 0.13 mass% C is investigated. The low carbon steels possess the higher Ms temperature than the high carbon steels, so that the packet size of the martensite structure is larger in the low carbon steels. Both the FATT (fracture appearance transition temperature) and the USE (upper shelf energy) increase with decreasing carbon content. This means the decrease of toughness and the increase of ductility with decreasing carbon content. Fine precipitates of the Laves phase are observed in the martensite lath in all experimental steels after quality heat treatment. The tensile strength measured at 873 K has a tendency to increase with decreasing C content. But a certain amount of C is needed even in 5 W ferritic steels to keep the longer creep-rupture life under the lower stress level.

Fracture toughness behavior of W-Ni-Fe sintered alloys with three strength levels was investigated. With increasing tensile strength, dynamic fracture toughness Kld decreases dramatically, especially in the upper shelf. In low strength material, cracks propagate by the coalescence of boids created in binder, whereas in high strength material, cleavage fractures of W particles precede the void formation of binder. Fracture toughness Kmax significantly depends on specimen size. The Kmax increases with increasing specimen size, which is caused by larger amount of stable crack extension in larger specimens. No effect of loading rate on Kmax was observed.Relationship between the Charpy absorbed energy and dynamic fracture toughness was also investigated.

The flow characteristics of fine particles in a spouted bed with a draft tube have been studied by measuring the solid hold-up in the draft tube, the bypass flow rate in the annulus, and the solids circulation rate. It was found that the gas-solid flow in the draft tube was the transport bed at high total gas flow rates.The bypass flow rate in the annulus decreased with the total gas flow rate to a minimum and then increased with further increase in the flow rate.On the other hand, the solids circulation rate increased with the total gas flow rate to a maximum and then decreased with further increase in the flow rate.An empirical equation for the maximum solids circulation rate was proposed, which almost agreed with the measued ones.

Rotating bending fatigue tests were carried out on the notched specimens of cast stainless steels. We prepared fine and coarse grain size materials in order to investigate the effect of grain size on the notched fatigue strength. The main results are summarized as follows : (1) The notch radii of the branch point ρ0 are nearly 0.3 mm, independent of grain size. (2) The master curves of Ktσw2 vs 1/ρ of the two materials are nearly equal, but the master curve of Ktσw1 vs 1/ρ of fine-grain-size material is somewhat higher than that of coarse-grain-size material. (3) When the notch radius is larger than about 2.5 mm, the notched fatigue strength of cast stainless steels decreases by the effect of a microshrinkage cavity.

Isothermal aging test of NiCrMoV rotor steel was carried out up to 100 000 h and change in the Charpy transition behavior was investigated. The test result revealed considerable embrittlement of the steels tested. Even at 343°C, the embrittlement of around 100°C was observed and higher temperature enhanced the embrittlement significantly. This embrittlement behavior strongly depends on the impurity contents of the materials and temper embrittlement parameter J factor or X well characterize the temper embrittlement susceptibility. Based on these test results, the amount of the temper embrittlement can be estimated from the information of chemistry. A correlation between the step cooling embrittlement and 100 000 h embrittlement was also found.

単分散粒子と見なせる平均径206μmの球形セラミック粒子と平均径37μmの球形セラミック粒子とを用い, 層温度300K, 600K, 900Kにおける最小流動化速度と気泡径に及ぼす微粉の影響について実験的に検討した.最小流動化速度は圧力損失法より決定し, 気泡径はVTR法を用いて測定した.その結果, 最小流動化速度は予測されたように流動層内の微粒子量の増加と層温度の上昇とともに減少することが示された.微粒子は流動層に小さな気泡を発生させるような効果を及ぼした.すなわち, 気泡径は層内の微粒子量が増加するとともに減少した.また, セラミック粒子を層物質として用いた流動層では温度の効果は認められなかった.

Here we describe the finding that oolong tea and black tea act as excellent carbon nanotube solubilizers to produce individually dissolved single-walled carbon nanotubes (SWNTs), which have been revealed using visible-near IR absorption, photoluminescence and Raman spectroscopy as well as AFM study. The oolong tea solution has a tendency to individually dissolve metallic SWNTs that can be detected by 514 nm-excition, and in solution, the (11,3)SWNTs enriched and (11,0)SWNTs that are contained in as-produced SWNTs were very few. Black tea solution shows similar tendency, while the separation performance was weaker compared to that of the oolong tea. We also used epigallocatechin gallate to solubilize the SWNTs and shed light on the mechanism of the SWNT dissolution. Tea contains numerous components with antioxidant activities; therefore biological and biomedical applications using the present soluble nanotubes might be of interest.

In order to obtain the improved strength and toughness for high-pressure low-pressure rotor shaft forging, fundamental studies using laboratory heats were performed on the 9CrMoV base materials, and effects of chemistry on toughness and creep rupture strength were investigated. From the investigation, it is showed that the superclean 9CrMoVNiNbN steel with reduced Si and Mn contents and Ni addition provides a superior strength versus toughness balance. Based on these fundamental studies, a trial high-pressure low-pressure rotor shaft forging with diameter of low-pressure section of 1750 mm and diameter of high-pressure section of 1200 mm was successfully manufactured from the diameter of 1800 mm, and the weight of 65 ton ESR ingot. From the evaluation test results of this trial rotor forging, homogeneous distribution of chemistry was confirmed and low impurity contents was observed in the whole forging. The superior strength and toughness were confirmed with good creep rupture strength. The FATT at the center of low-pressure section was -3°C with the tensile strength level of 870 MPa. From the results of fracture toughness test, low cycle fatigue test, and isothermal aging test, superior mechanical properties were demonstrated. Thus, the superclean 9CrMoVNiNbN steel with reduced Si and Mn contents and Ni addition, is particularly suitable to the high-pressure low-pressure rotor material for advanced combined cycle power plants.

An advanced 12% chromium ferritic steel has been developed for the high-temperature rotors in improved fossil-fired power plants. The development of this steel is based on the experimental studies of various 12% chromium heat resistant steels. Effects of alloy elements on the creep rupture strength have been investigated and the 10Cr-1.8W-0.7Mo-V-3Co-Nb-B steel was selected to be a hopeful candidate. This revealed the creep rupture strength was higher than that of 10Cr-1Mo-1W-V-Nb rotor steel being used at 593°C. The producibility and properties of the new steel have been verified with the medium size trial forging manufactured from a 20 ton ingot. Although a few technical subjects are remaining, these are expected to be solved with the modification of the manufacturing process. This newly developed high strength 12 % chromium ferritic steel is expected to be applicable to high-temperature rotors operating at 630°C or above, and the significant improvement of thermal efficiencies would be obtained in fossil-fired power plants.

Fatigue crack growth rates (da/dN) in up to 90MPa high-pressure gaseous hydrogen environments of quenched and tempered low alloy Cr-Mo steel: JIS-SCM435 with ultimate tensile strength level of 950MPa were measured utilizing a cycle, ranging from 0.3sec from 1000sec long with a road ratio R = 0.1. The longer cycle time tests (15sec to 1000sec per cycle) were conducted utilizing internal pressure test apparatus by utilizing cylinder (= CY) specimens, while shorter cycle (0.3sec to 25sec per cycle) tests were performed utilizing fatigue test machine using compact tension (= C(T)) specimens. Crack depth of CY specimens were measured by Time Of Flight Diffraction (TOFD) technique and the crack length of C(T) specimens were measured by compliance technique. Both C(T) and CY specimen showed accelerated sub-critical crack growth in gaseous hydrogen compared that in air or inert gas atmosphere. The effect of load ratio was also evaluated.Copyright © 2009 by ASME

A semi-cylindrical fluidized bed of 15 cm internal diameter, equipped with a transparent flat glass plate for the front wall, was employed to visually observe bubbles in the bubbling to slugging transition regime and in the slugging regime. Five kinds of perforated distributors were used to investigate the effect of distributor type on the bubble size and the bubble rise velocity. The average bubble size was not affected by distributor type in these flow regimes, and could be predicted by Darton et al's correlation (1974)of hole number 22. In other words, this comes from the inapplicability of the correlation to the slugging regime. The bubble rise velocity agreed well with Allahwala et al's correlation (1979) and was not affected by the type of distributor.

The solids holdup within the riser of a circulating fluidized bed (CFB) with twocomponent particles was measured. Iron powders and silica sand, which are of nearly the same diameter but different in density, were mixed and fluidized.A correlation was proposed to estimate the axial solids holdup within the riser by considering superficial gas velocity, solids circulation rate and initial concentration of iron powder.

To provide engineering data useful in design, manufacture and operation of hydrogen storage vessels in hydrogen refueling stations, fatigue test machine equipped with high-pressure hydrogen autoclave was introduced. The effect of steel’s strength level, temperature effect, fracture toughness and pressure effect were evaluated in gaseous hydrogen environment. When steel’s strength level exceeds around 930MPa to 1000MPa, the elongation and notch tensile properties deleteriously degraded. The elongation reduction by the effect of hydrogen increased with lowering the temperature. The same sensitivity to temperature on crack growth behavior was observed. However, it was shown that the gaseous hydrogen environment only affect the slow stable crack growth but did not affect the critical flaw growth of the steel at low temperature, i.e. fast fracture. The pressure dependence of notch tensile strength ranging from 0.1MPa to 75MPa hydrogen pressure shows approximately 1/2 power dependence.Copyright © 2007 by ASME

The effect of surface machining on fatigue life in high pressure hydrogen gas was investigated. The test was conducted under the elastic range under 45MPa gaseous hydrogen environment by the ground specimen which were machined so that the surface roughness to be Rmax = 19μm(Mark: 19s), 26μm(26s) and 93μm(93s) and by the polished specimen which are prepared so that the surface roughness to be Rmax = 1μm(1s), 3.6μm(3.6s) and 10μm(10s). The hydrogen fatigue life of ground specimens was considerably reduced with increasing surface roughness as compared to the fatigue life in air at the same surface condition. On the other hand, for the annealed conditions of the ground specimen, the reduction by hydrogen effect was fairly small. The residual stress for the ground specimen at the surface rises sharply in tension while the residual stress for the annealed specimen was nearly equal to zero. We have shown that the hydrogen fatigue damage can be evaluated by obtaining the information about residual stress on surface, stress concentration by maximum surface roughness and the threshold stress intensity SH above which hydrogen fatigue damage occurs.Copyright © 2007 by ASME

In order to study the behavior of crack opening displacement at the maximum load, CODmax, per British Standard 5762, the COD tests were conducted using 3.7% Ni-Cr-Mo-V steel in the upper shelf region. The test results obtained are as follows.(1) The CODmax value depends on the specimen size and yield strength of the material.(2) The CODmax value increases with increasing specimen size, of which the tendency is remarkable in the material with lower yield strength.(3) When the yield strength increases, the CODmax value decreases, especially more remarkable in the larger specimen.(4) The following correlation between CODmax and 2mm V-notch Charpy impact energy is confirmed.CODmax/σY=m'(CVN-us/σY-0.11)(5) The constant m' depends on the specimen thickness B.m'=0.010√B

In order to study the origin of the scatter in the fracture toughness values by small specimens in the transition region, the J-integral measurement in the fracture toughness transition region was performed using more than 100 small specimens of Ni-Cr-Mo-V steel, and fractured surfaces were studied very carefully, aiming to obtain better understanding of the scatter in the small-specimen toughness. The study discloses that a major portion of the scatter was caused by the scatter in the length of the preceding dimple crack, which was generated at the fatigue precrack before the initiation of the final cleavage fracture. A method to predict the lower bound of the scatter in the small-specimen fracture toughness was also proposed.

In order to study the origin of the scatter in the fracture toughness in the transition region and to specify the lower bound of the scatter, approximately 100 pieces 0.5T-CT NiCrMoV steel specimens were tested in the transition region, and their fracture surfaces were investigated. Major portion of the scatter was caused by the scatter in the length of preceding dimple crack which was generated at the fatigue precrack before conversion to final cleavage fracture. A method to predict the lower bound of the scatter in the small-specimen fracture toughness was proposed. It employs Weibull plot of new parameter J 1 which represents the scatter in the cleavage strength of material. The cleavage fracture origin may be associated with micro-stress-concentration in the microstructure which may not be caused by the micromechanism in terms of grain size unit.

Glass beads of four sizes were fluidized in a spouted bed comprising a 50 mm-diameter transparent acrylic column and a coaxial draft tube. Draft tube diameter, separation distance and particle size were varied and spouting states were observed.It was found that stable spouting occurred when the air velocity in the tube exceeded about 79% of particle terminal velocity. The correlation proposed to predict minimum stable spouting velocities was expressed as a function of the variables above and particle terminal velocity, and the predicted values agreed with experimental data within ± 11% deviation.

This paper presents a method to predict the fracture toughness KIc and/or KId of steels using their Charpy impact test results and tensile properties. The fracture toughness, Charpy impact and tensile properties of 21/4Cr-1Mo, ASTM A508 Cl.1, A508 Cl.2, A508 Cl.3 and A533 Gr.B Cl.1 steels were measured and analysed on the basis of the excess temperature (test temperature minus FATT) and Rolfe-Novak correlation. The relationship between KIc/KIc-us and the excess temperature, where KIc-us is the upper-shelf fracture toughness KIc predicted by Rolfe-Novak correlation, discloses that the KIc transition curves of several steels are representable by only one trend curve of KIc/KIc-us or KId/KId-us versus excess temperature relation. This curve is denoted as a “master curve”. By using this curve, the fracture toughness of steel can be predicted using Charpy impact and tensile test results. By taking account of the scattering of both the fracture toughness and Charpy impact test results, the confidence limits of the master curve were also determined. Another approach to develop more general procedure of predicting the fracture toughness KIc is also discussed.

The dynamic fracture toughness is the most critical parameter for the safety assessment of reactor pressure vessels. However, the measurement of the dynamic fracture toughness is very difficult because a special testing facility is required. For engineering use, the development of a method to predict the dynamic fracture toughness from small specimen tests is now strongly desired. One representative method for this aim is to use the correlation between the drop weight NDTT and the dynamic fracture toughness KId as set forth in ASME Code. However, the correlation does not work well because of difficulty in establishing an accurate one by scattering of NDTT due to the bead application on the drop weight specimen and by scattering of KId in the fracture toughness transition region. In this study, by taking account of these sources of scattering, the relationship between NDTT and dynamic fracture toughness was re-examined. The results revealed its definite dependence on the strength of the material used. On the other hand, the correlation between the Charpy index temperature and KId was not sensitive to the strength. This fact demonstrates the advantage of using FATT as the reference temperature to construct a master curve to predict KId. By using the data obtained, a single master curve, which can be used to predict the dynamic fracture toughness from the Charpy V-notch impact test results, was established for A508 Cl.3 and A533 Gr.B Cl.1 steels.

A rotary dust collector is a mechanical centrifugal separator provided with an internal rotor supplying a vortex.In this paper, comparisons are made of the performance characteristics of rotary dust collectors with a tangential and an axial inlet. The pressure drop through the device of the axial inlet type is lower than that of the tangential inlet type, while little difference is observed in an increase of the pressure drop with the rotor speed between the both types. The critical particle size calculated through application of simplifying assumptions is nearly proportional to the specific particle size corresponding to the cumulative weight fraction of oversize particles taken equal to the measured collection efficiency. The particle size ratio is constant, independent of the gas flow rate and rotor speed, and it is also independent of the rotor diameter in case of the tangential inlet type. In case of the axial inlet type, however, the ratio depends on the rotor diameter.In addition, the effect of the number of the rotor disks on the performance is compared for the rotors without bars on the periphery.