Chatter vibrations occurring in machining metals are of two kinds, forced and self-excited. The existence of each chatter is a serious problem, because it is detrimental to the life of tool, on the surface finish and etc. In order to prevent such chatter, some attempt has been made recently to apply a damper to machine tool. In this paper, the effect of Lanchester Damper for the prevention of each chatter was first examined theoretically, and the procedure of designing damper by which each chatter was effectually eliminated was discussed for any vibratory system. Then, the above theory was ascertained experimentally on a boring quill coupling with Lanchester Dampers. Consequently, it was made evident that the damper which was designed in optimum conditions had a conspicuous effect on the prevention of each chatter.
In this review, we summarize recent progress in experimental approaches to the investigation of the unoccupied electronic structures of organic ultrathin films, based on a combination of spectroscopic and microscopic techniques. At the molecule/substrate interface, electronic structures are greatly affected by the geometrical structures of adsorbed molecules. In addition, a delicate balance between substrate-molecule and intermolecular interactions plays an important role in the formation of complex polymorphism. In this context, we have clarified the correlation between geometric and electronic structures using a combination of two-photon photoemission (2PPE) spectroscopy, low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). Organic ultrathin films of metal phthalocyanines and polycyclic aromatic hydrocarbons (naphthalene, rubrene and perylene) on graphite substrates were examined as model systems. Depending on the substrate temperature and coverage, unique morphologies, including well-ordered films, a metastable phase and a two-dimensional gas-like phase, were determined at the molecular level. The data show that variations in molecular orientation have a significant impact on the occupied/unoccupied electronic structures. In addition to static information regarding electronic states, ultrafast electron excitation and relaxation dynamics can be tracked in real time on the femtosecond scale by time-resolved 2PPE spectroscopy. The excited electron dynamics of rubrene films are discussed herein, taking into account structural information, in the presence and absence of an overlap of the wave function with the substrate. Spatial resolution at the molecular level is also obtainable via STM-based local spectroscopy and mapping, which have been utilized to elucidate the spatial extent of unoccupied orbitals in real space. Visible photon emissions from the unoccupied states of perylene monolayer films were observed using 2PPE, representing a characteristic deexcitation process from electronically excited states, depending on the surface structure. These spectroscopic and molecular level microscopic investigations provide fundamental insights into the electronic properties of organic/substrate interfaces.
We have measured angle- and time-resolved two-photon photoemission (2PPE) from unoccupied levels of graphite (HOPG) and lead phthalocyanine (PbPc) films. Our angle-resolved 2PPE microspot spectroscopy with a lateral resolution of 0.4 μm can effectively select flat and homogeneous regions of the film, allowing measurements of the dispersion of the image potential state (IPS) on the PbPc film. The effective mass of the IPS on the film is 2.2 ± 0.2, which is heavier than that for the bare HOPG, 1.2 ± 0.1. The lifetimes of the states at 30 K are 30 fs for both the HOPG and the PbPc film. These results suggest a hybridization of the IPS with a molecule-derived unoccupied level. The lifetimes of the lowest unoccupied molecular level (LUMO)-derived levels are about 80 fs. A possible decay process to lower states is suggested.
Cation-deficient copper chalcogenide nanocrystals (NCs) as a typical degenerated semiconductor have attracted great attention owing to their unique properties. However, the association between band structures and localized surface plasmon resonance (LSPR) in such NCs has not been thoroughly studied. Moreover, the synthesis of the colloidal Cu2–xSeyS1–y NCs with diverse crystal phases remains a challenge to date. Hence, we developed a facile method to synthesize a range of Cu2–xSeyS1–y-alloyed NCs with disparate crystal phases. We elucidated the tunable band structures and LSPR shift, and the results indicated that the modulation of the valance band maximum (VBM) position by Se/S alloying and the overlapping of the valence band and the Fermi level (EF) dominate LSPR properties in alloyed NCs. Not only the variation of Cu vacancy along with the induced free carrier concentration but also the negative shift of VBM contribute to the LSPR shift toward higher energy.
We have explored the superior radiation tolerance of metal organic chemical vapor deposition (MOCVD) grown, low bandgap, (0.95 eV) InGaAsP solar cells as compared to GaAs-on-Ge cells, after 1 MeV electron irradiation. The minority carrier injection due to forward bias and light illumination under low concentration ratio, can lead to enhanced recovery of radiation damage in InGaAsP n + -p junction solar cells. An injection anneal activation energy (0.58 eV) of the defects involved in damage/recovery of the InGaAsP solar cells has been estimated from the resultant recovery of the solar cell properties following minority carrier injection. The results suggest that low bandgap radiation resistant InGaAsP (0.95 eV) lattice matched to InP substrates provide an alternative to use as bottom cells in multi-junction solar cells instead of less radiation ressitant conventional GaAs based solar cells for space applications.
10 Gbps operation of BTJ GaInNAs VCSELs is achieved over temperature range of 25degC to 100degC with operation current of 5.6 mA and extinction ratio of 4.2 dB.
To examine the elementary steps of the Rochow-Müller process we placed copper oxides, viz., Cu2O(1 1 1) and the bulk Cu2O precursor "29"-structure on Cu(1 1 1), under supersonic molecular beams (SSMB) of CH3Cl. The SSMB energies range from 0.5-1.9 eV. We employed X-ray photoemission spectroscopy (XPS) in conjunction with synchrotron radiation (SR) to determine the resulting adsorbed species present. We identified two reaction paths, viz., Reaction I and Reaction II. Reaction I involves dissociative adsorption of CH3Cl. In Reaction II, CH3Cl also dissociates, but with Cl as the dominant adsorbed species (higher than that of adsorbed carbonaceous species, as observed for Reaction I). For the incident energies and exposure conditions considered, we found Reaction II as the dominant reaction path for CH3Cl reaction on both Cu2O(1 1 1) and the "29"-structure on Cu(1 1 1).
In this paper, we discuss the solution of the linear system of equations derived from a finite element electromagnetic field simulation of a practical model in which the electromagnetic field is analyzed with effects of external circuits. To solve the linear system of equations efficiently, we introduce two preconditioning techniques recently proposed for Krylov subspace method. One is folded preconditioning and the other is A-phi block IC preconditioning. The A-phi block IC preconditioning is also one of folded preconditioning methods. Through practical simulation models, we examine these preconditioning techniques and confirm their effectiveness. Furthermore, we present a strategy for selecting the appropriate preconditioning technique, focusing on the magnitude of nonzero elements in non-diagonal blocks of the coefficient matrix.
Long-wavelength GaInNAs lasers grown on GaAs are very attractive devices for the application of optical communication. Recently, excellent high temperature characteristics and low threshold current density operation have been reported. However, the threshold current is still not low enough for practical applications at 1.3 /spl mu/m region. This is mainly due to the difficulty of forming an effective current confinement structure. In this paper, we present successful operation of GalnP buried heterostructure devices emitting over 1.3 /spl mu/m with very low threshold current ever reported. Organometallic vapor phase epitaxy (OMVPE) selective buried growth was used for the fabrication of the device.
A qualitative and quantitative gustometric testing method using the filter paper disc on sweet, salty and sour tastes was evaluated in 30 patients with diabetes mellitus (type II, NIDDM) and in 30 healthy subjects (volunteers) in our hospital.The following results were obtained in this study.1) The threshold of salty and sour tastes in diabetic patients obviously elevated in contrast to those in healthy subjects.2) The total score which was calculated by the sum of each score about sweet, salty and sour tastes, significantly lowered in diabetic patients (diabetes vs healthy; 18.5±8.9 vs 27.4±9.6, p<0.01), especially so in the patients with complications with microangiopathies (diabetes vs healthy; 13.1±11.7 vs 27.4±9.6, p<0.01).3) Patients who have been afflicted with diabetes for more than 10 years show the lower total scores of three tastes compared to those who have suffered the disease for less than 10 years (more than 10 years vs less than 10 years; 11.0±10.5 vs 20.6±7.2, p<0.01).4) The total scores rose considerably in some of diabetic patients after the improvement of fasting blood glucose levels by diet alone (before vs after; 16.5±8.3 vs 23.0±6.6, p<0.01).It is concluded that the gustometric testing method using the filter paper disc may be useful in clinical evaluation of the taste impairment in patients with diabetes mellitus.
