A Method for Structuring Service Failure Factors to Realize Highly Reliable Services

As the society matures, customer requirements have become more varied. Services have been attracting increasing attention from industry and academic field as an effective mean to satisfy such varied customer requirements. In order to make a profit, it is important for companies to build and maintain long-term relationships with customers. Therefore, service providers should maintain their service quality and always satisfy their customers. To realize highly reliable product or services, in general, it is an effective approach to prevent failures from occurring in the use phase. Therefore, it is necessary that analysts identify the factors that could cause service failure and take appropriate measures against the target failure factor in advance. However, service failure factors are varied compared to physical products because service failures occur due to uncertainty elements such as human factors. In this study, we aim to enable service analysts to identify the critical failure factor from a number of failure factors. To achieve this, we identify complex failure factors and relationships among them from the viewpoint of the field where the service provided. This paper proposes a method for structuring the causal sequence between service failure factors by using a method of system modeling.     

Enhanced performance of organic light-emitting diodes by inserting wide-energy-gap interlayer between hole-transport layer and light-emitting layer

We demonstrated that driving voltages, external quantum efficiencies, and power conversion efficiencies of organic light-emitting diodes (OLEDs) are improved by inserting a wide-energy-gap interlayer of (4,4′-N,N′-dicarbazole)biphenyl (CBP) between a hole-transport layer of N,N-di(naphthalen-1-yl)-N,N′-diphenyl-benzidine (α-NPD) and a light-emitting layer of tris(8-hydroxyquinoline)aluminum. By optimization of CBP thicknesses, the device with a 3-nm-thick CBP layer had the lowest driving voltage and the highest power conversion efficiency among the OLEDs. We attributed these improvements to enhancement of a carrier recombination efficiency and suppression of exciton–polaron annihilation. Moreover, we found that the degradation of the OLEDs is caused by decomposition of CBP molecules and excited-state α-NPD molecules.     

Plasma-polymerized films providing selective affinity to the polarity of vaporized organic solvents

Plasma-polymerized films (PPFs) were fabricated as recognition membranes for a vapor-sensing device, and their affinity to vaporized organic solvents was evaluated with surface plasmon resonance. The affinity we intended to create is the selective sorption of the vaporized organic solvents depending on their polarity. For this purpose, acetonitrile, ethylenediamine (EDA), styrene, hexamethyldisiloxane (HMDSO), and hexamethyldisilazane were used to fabricate PPFs. Vaporized methanol, ethanol, and 1-propanol were used as high-polar solvents to be analyzed. Hexane, toluene, and p-xylene were used as low-polar solvents. As a result, the HMDSO-PPF with 97.3° of contact angle was found to provide affinity to the low-polar solvents. In contrast, the EDA-PPF with 7.1° of contact angle provided affinity to the high-polar solvents. Observations of the surface morphology of the HMDSO- and EDA-PPFs with a scanning electron microscope revealed that they are composed of nano-scale islands.     

UV-induced switching behavior of novel fluoroalkyl end-capped vinyltrimethoxysilane oligomer/titanium oxide nanocomposite between superhydrophobicity and superhydrophilicity with good oleophobicity

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer suffered the sol–gel reaction under alkaline conditions in the presence of titanium oxide nanoparticles in tetrahydrofuran to afford the corresponding fluorinated oligomer/titanium oxide nanocomposites[R_F-(VM-SiO₂)_n-R_F/TiO₂] in excellent to moderate isolated yields. These fluorinated composites thus obtained were nanometer size-controlled fine particles, and exhibited good dispersibility and stability in traditional organic solvents except for water. These fluorinated nanocomposites were applied to the surface modification of glass to exhibit not only a completely superhydrophobic characteristic (a water contact angle: 180°) with a non-wetting property against water droplets but also a good oleophobicity imparted by fluoroalkyl segments in the composites on their surface. Of particular interest, we have found that the wettability for water can be switched between superhydrophobicity and superhydrophilicity by alternation of ultraviolet (UV) irradiation and dark storage with keeping a good oleophobicity on the modified surface treated with the anatase-type titanium oxide composite.     

Features of the mechanism of electrical conductivity of semiinsulating CdTe crystals

Temperature dependence of electrical characteristics of p-CdTe semi4nsulating single-crystals are studied, and substantial features of their electrical conductivity not described in available publications are revealed. The activation energy of the p-type conduction material close to the intrinsic one can be both lower and higher than the half-width of the band gap of semi conductor. The results of the analysis of statistics of electrons and holes based on the electroneutrality equation showed that the observed features of electrical properties of the material can be interpreted based on the specific features of compensation processes. The procedure of determining the ionization energy and degree of compensation of acceptors responsible for electrical conductivity of the material is suggested. It is shown that, in the limits of climatic temperature variations, inversion of the conduction type can be observed, and, as a consequence, the Schottky contact can disappear in the CdTe-based detector of the X-ay and γ radiation.     

Physical modelling and similitude of air bubble entrainment at vertical circular plunging jets

When a plunging jet impinges into a pool of liquid, air bubble entrainment takes place if the inflow velocity exceeds a threshold velocity. This study investigates air entrainment and bubble dispersion in the developing flow region of vertical circular plunging jets. Three scale models were used and detailed air-water measurements (void fraction, bubble count rate, bubble sizes) were performed systematically for identical inflow Froude numbers. The results highlight that the modelling of plunging jet based upon a Froude similitude is affected by significant scale effects when the approach flow conditions satisfied We₁<1E+3, while some lesser scale effect was noticed for V₁/u_r<10 and We₁>1E+3. Bubble chord time measurements showed pseudo-chord sizes of entrained bubbles ranging from less than to more than with an average pseudo-chord size were between 4 and . However, bubble size data could not be scaled properly.     

Design of passivity‐based stabilized control of grid‐connected inverter system with LCL filter

Instabilities due to mutual interactions between inverters and grid impedance are observed sometimes. This paper proposes a new stabilization method, which improves the output frequency impedance characteristics, satisfying the Nyquist stability criterion. The principle is that the output impedance is designed to be passive with the feedfoward loop characteristics and the system is stable even for an unknown grid system impedance. The design principle for the proposed stabilization method is described and investigated and validated on the basis of simulation and experimental results.