Synthesis and structures of iron nanoparticles coated with boron nitride nanomaterials

Iron (Fe) nanoparticles coated with boron nitride (BN) nanomaterials were synthesized by using Fe(4)N and B powders as raw materials. The Fe(4)N was reduced to alpha-Fe during annealing at 1000 degrees C for several hours with flowing 100 sccm N(2) gas. The reaction was predicted by Ellingham diagram. The atomic structure and magnetic properties were investigated by high-resolution electron microscopy and vibrating sample magnetometer system.     

Dielectric function and the crystal structure of MeV ion implanted LiNbO3

The behavior of the dielectric functions of MeV ion-implanted LiNbO₃ was studied using THz spectroscopy. Single crystal LiNbO₃ specimens were implanted with 3 MeV Au ions at four different levels of ion fluence (1 × 10¹², 1 × 10¹³, 1 × 10¹⁴ and 1 × 10¹⁵ cm^− 2). The optical spectra of the specimens were then measured in two ranged values: (1) reflectance THz range spectra from 40 to 700 cm^− 1 and (2) reflectance ultraviolet, visible, and near-infrared spectra from 250 to 2000 nm. The THz spectra were analyzed by fitting with the dielectric function model proposed by Brendel. The dielectric function model explained well the experimental spectra of the ion-implanted LiNbO₃. The dielectric function shows that the ion-implanted layers were amorphous phase at the fluence of 1 × 10¹⁴ and 1 × 10¹⁵ cm^− 2, whereas the layers at 1 × 10¹² and 1 × 10¹³ cm^− 2 maintained the crystal phase but significantly suppressed the phonon resonances. The volume of ion-implanted layers expanded about 8% with the fluence of 1 × 10¹⁴ and 1 × 10¹⁵ cm^− 2, i.e. after amorphization, These results show that the ion implantation significantly affected the lattice vibration mode and the structure even at very low ion fluence.     

Safety performance of the 4S reactor on the ATWS events – statistical estimation of uncertainty

4S reactor is a sodium-cooled fast reactor developed as a small-decentralized power supply. The name of “4S” in this reactor stands for Super-Safe, Small and Simple, and they show representative features of the reactor.

The purpose of the present work is to evaluate quantitatively the super-safety of 4S reactor, and the safety performance is analyzed with ARGO-3, which is a plant dynamics code of a sodium-cooled fast reactor.

In this evaluation, some events, such as Unprotected Loss of Flow (ULOF) and Unprotected Transient Overpower (UTOP), are selected as typical cases from various transients and accidents. After metrics concerned with safety design is defined for each event, it is evaluated with statistical methods whether each metric satisfies acceptance criteria in a given criteria level.

Result about ULOF is as follows. The coolant temperature in the nominal hottest assembly outlet, “T_c” is selected as metric, and the upper side value of 95% confidential section in T_c is below 900 °C that is acceptance criteria. Also in UTOP, it is shown that the fuel maximum temperature in the nominal hottest assembly, “T_f” satisfies acceptance criteria. This result shows that 4S reactor has margin for safety acceptance criteria.     

Detection and Diagnosis of Plant‐Wide Oscillations

This paper presents some emerging techniques for detection and root‐cause diagnosis of plant‐wide oscillations, and demonstrates their efficacy through a successful industrial case study. The recently proposed autocorrelation function based method (Thornhill et al., J. Proc. Control 13, 91–100, 2003a) is used for detection of oscillations in the process measurements. Signals having common oscillations are analyzed for the presence of valve stiction using higher order statistical methods (Choudhury et al., Automatica 40, 1719–1728, 2004b) . A method employing changes in controller gain is proposed for distinguishing an internally generated oscillation from an external oscillatory disturbance. This method of changing controller gain is used to confirm the presence of control valve stiction. The proposed techniques have been used successfully to identify the root cause of plant‐wide oscillations in an industrial case study using routine operating data.     

Sound design for emotion and intention expression of socially interactive robots

The current concept of robots has been greatly influenced by the image of robots from science fiction. Since robots were introduced into human society as partners with them, the importance of human–robot interaction has grown. In this paper, we have designed seven musical sounds, five of which express intention and two that express emotion for the English teacher robot, Silbot. To identify the sound design considerations, we analyzed the sounds of robots, R2-D2 and Wall-E, from two popular movies, Star Wars and Wall-E, respectively. From the analysis, we found that intonation, pitch, and timbre are dominant musical parameters to express intention and emotion. To check the validity of these designed sounds for intention and emotion, we performed a recognition rate experiment. The experiment showed that the five designed sounds for intentions and the two for emotions are sufficient to deliver the intended emotions.     

Speed estimation for very low speed systems

This paper discusses the problem of speed estimation in very low speed servo systems. Speed estimation can be easily done by such conventional tools as tachometers, observers, numerical differentiation, and so on. However, speed estimation for very low speed systems still includes some engineering problems regarding precision. This paper proposes a simple way to derive a speed estimate by using the output difference over a long period of time and the sequence of inputs during the same period. We have also verified this method through an experiment on a hydraulic servo system. © 1999 Scripta Technica, Electr Eng Jpn, 126(4): 63–69, 1999     

Molecular simulations of cluster ejection by CO2 cluster impact on carbon-based surfaces

Single (CO₂)_N (N = 1-20) cluster impact on three different carbon-based surfaces of fullerite (1 1 1), graphite and diamond (1 0 0) has been investigated by MD simulations with the cluster collision energy from 5 to 14 keV/cluster as a first step toward the general modeling of the reactive sputtering by cluster impact of a solid surface. A crater permanently remained on the fullerite and graphite surfaces while it was quickly replenished with fluidized carbon material on the diamond surface. In spite of the smaller crater size as well as the crater recovery resulting in the reduction of the surface area, the sputtering yields were the highest on diamond. The effective energy deposition near the surface contributes to the temperature rise and consequent sputtering seemed highly reduced due to the collision cascades especially on the fullerite target.     

Bioaccumulation of organochlorines in crows from an indian open waste dumping site: evidence for direct transfer of dioxin-like congeners from the contaminated soil

To assess the significance of waste dumping sites as a source of chemical contamination to ecosystems, we analyzed the residue levels of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and other organochlorines in the breast muscle of crows from a dumping site in the south of Chennai city, South India. Crows from the dumping site contained significantly higher total TEQs (60 +/- 27 pg/g lipid wt) than those from the reference sites (26 +/- 18 pg/g lipid wt). Especially, certain dioxin-like coplanar PCB congeners (Co-PCBs), such as CB-77 and CB-105, whose source is commercial PCBs,were significantly higher in crows from the dumping site than those from the reference sites. Profiles of PCDDs/DFs and Co-PCBs in crows from the dumping site were similar to those of soil at the same site, which was confirmed by principal component analysis. Furthermore, significant positive correlations were obtained between the congener-specific bioconcentration factors (BCFs) of PCDDs/DFs estimated from concentrations in crows and soil from the dumping site and the theoretical BCFs calculated from water-particle and lipid-water partitioning coefficients. On the other hand, the estimated BCFs had significant negative correlations with the molecular weight of PCDDs/DFs, indicating that molecular size limits their bioaccumulation. These results suggest that dioxin-like congeners in the soil of the dumping site were transferred directly to the crows through the ingestion of on-site garbage contaminated with soil, rather than through trophic transfer in the ecosystem. The present study provides insight into the ecological impacts of dumping sites.     

Cobalt-based bulk glassy alloy with ultrahigh strength and soft magnetic properties

Bulk metallic glasses--formed by supercooling the liquid state of certain metallic alloys--have potentially superior mechanical properties to crystalline materials. Here, we report a Co(43)Fe(20)Ta(5.5)B(31.5) glassy alloy exhibiting ultrahigh fracture strength of 5,185 MPa, high Young's modulus of 268 GPa, high specific strength of 6.0 x 10(5) Nm kg(-1) and high specific Young's modulus of 31 x 10(6) Nm kg(-1). The strength, specific strength and specific Young's modulus are higher than previous values reported for any bulk crystalline or glassy alloys. Excellent formability is manifested by large tensile elongation of 1,400% and large reduction ratio in thickness above 90% in the supercooled liquid region. The ultrahigh-strength alloy also exhibited soft magnetic properties with extremely high permeability of 550,000. This alloy is promising as a new ultrahigh-strength material with good deformability and soft magnetic properties.