Effective lightning protection schemes for distribution line

The causes of lightning outage are subdivided into direct lightning strokes and induced lightning strokes, which are identified by the characteristics of the lightning overvoltage. In the past, lightning protection devices were directed mainly toward the latter, and attention has been focused on the installation of lightning protection devices, ground wires, and reinforcement of insulators. However, lightning outages continue to occur. Thus it is extremely important to clarify the fault characteristics of lightning surges and to study the effectiveness of various lightning protection devices by considering both direct lightning stroke and induced lightning stroke in order to prevent lightning outage in the future. In this research, the electromagnetic transients program (EMTP) has been applied to the direct lightning stroke, and the induced lightning outage analysis program for multiple conductor systems has been applied to the induced lightning stroke to study the effectiveness of lightning protection devices provided by combination of various lightning protection devices. The most effective lightning protection schemes are analyzed and evaluated based on verification tests on the full scale models as well as economic considerations.     

NiCoFe/C cathode electrocatalysts for direct ethanol fuel cells

A direct ethanol fuel cell (DEFC), which is less prone to ethanol crossover, is reported. The cell consists of PtRu/C catalyst as the anode, Nafion^® 117 membrane, and Ni–Co–Fe (NCF) composite catalyst as the cathode. The NCF catalyst was synthesized by mixing Ni, Co, and Fe complexes into a polymer matrix (melamine-formaldehyde resins), followed by heating the mixture at 800 °C under inert atmosphere. TEM and EDX experiments suggest that the NCF catalyst has alloy structures of Ni, Co and Fe. The catalytic activity of the NCF catalyst for the oxygen reduction reaction (ORR) was compared with that of commercially available Pt/C (CAP) catalyst at different ethanol concentrations. The decrease in open circuit voltage (V_oc) of the DEFC equipped with the NCF catalysts was less than that of CAP catalyst at higher ethanol concentrations. The NCF catalyst was less prone to ethanol oxidation at cathode even when ethanol crossover occurred through the Nafion^®117 film, which prevents voltage drop at the cathode. However, the CAP catalyst did oxidize ethanol at the cathode and caused a decrease in voltage at higher ethanol concentrations.     

Polymerization of epoxide with aluminum complex/silanol catalyst. VII. Thermal and electrical properties of epoxy resin cured with the new catalyst

Curing catalyst for epoxy resins was newly found. The catalyst consists of aluminum complex and silanol. Lack of one component of the pair does not cure epoxy resins. The epoxy resins cured with the catalyst are characterized by excellent electrical properties, especially at high temperature, due to the absence of strong acid species in the cured epoxy resin matrix. Heat-resistant property of the resin was also excellent. These properties were compared with those of epoxy resin cured with commonly used BF₃ complex.     

OBDDs of a Monotone Function and Its Prime Implicants

Coudert made a breakthrough in the two-level logic minimization problem with Ordered Binary Decision Diagrams (OBDDs for short) recently [3]. This paper discusses the relationship between the two OBDDs of a monotone function and its prime implicant set to clarify the complexity of this practically efficient method. We show that there exists a monotone function which has an O(n) size sum-of-products but cannot be represented by a polynomial size OBDD. In other words, we cannot obtain the OBDD of the prime implicant set of a monotone function in an output-size sensitive manner once we have constructed the OBDD of that function as in [3], in the worst case. A positive result is also given for a meaningful class of matroid functions. Received April 1997, and in revised form December 1997, and in final form February 1998.     

Frictional properties of an immobilized fluorinated polymer nanosheet

The frictional properties of an immobilized fluorinated polymer nanosheet were investigated to develop an ultrathin solid lubrication film with an excellent wear-resistant. N-(1H,1H-Pentadecafluorooctylmethacrylamide) copolymers containing carboxyl group as a reactive moiety form a stable monolayer on the water surface and a highly ordered reactive fluorinated polymer nanosheet can be fabricated by the Langmuir-Blodgett technique. The reactive fluorinated polymer nanosheet was immobilized onto solid substrates through chemical binding with an aminosilane coupling agent, and the film showed smooth surface even after the reaction. The immobilized fluorinated polymer nanosheet had a low friction coefficient and strong wear-resistant.     

Anisotropic in vitro vessel model using poly(vinyl alcohol) hydro gel and mesh material

In the present study, the authors fabricated straight multilayer hybrid tubular in vitro vessel models (inner diameter D_in = 10 mm; thickness T = 4 mm) composed of poly(vinyl alcohol) hydrogel (PVA‐H) and anisotropic mesh materials. The authors performed tensile, stress‐relaxation and cyclic‐tensile tests using axial and circumferential test pieces as well as pressure‐diameter (P‐D) tests using tubular test piece. In the tensile and stress‐relaxation tests, the anisotropic and nonlinear mechanical properties and hysteresis characteristic of the in vitro models were confirmed. The in vitro models also showed behavior qualitatively similar to that of native arteries in cycle‐tensile and P‐D tests. These results demonstrate that the mechanical properties of native vessels can be duplicated in an in vitro model by controlling the components of the mesh material, the orientation of elastic fibers in the mesh material, and the concentration and thickness of PVA‐H layers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Isolation and characterization of poly(butylene succinate-co-butylene adipate)-degrading microorganism

Poly(butylene succinate-co-butylene adipate) (PBSA)-degrading bacterium, strain 1-A, was isolated from soil. Strain 1-A was identified as Bacillus pumilus on the basis of its physiological properties and partial 16S rRNA gene sequence. Strain 1-A also degraded poly(butylene succinate) (PBS) and poly(epsilon-caprolactone). On the other hand, poly(butylene adipate terephthalate) and poly(lactic acid) were minimally degraded by strain 1-A. The NMR spectra of degradation products from PBSA indicated that the adipate units were more rapidly degraded than 1,4-butanediol and succinate units. This seems to be one of the reasons why strain 1-A degraded PBSA faster than PBS.