Clarification of the SSR mitigation mechanism of a TCSC

A thyristor controlled series capacitor (TCSC) is considered to be effective not only for flow control and stabilization of power systems, but also for mitigation of subsynchronous resonance (SSR). This paper clarifies the SSR mitigation mechanism of a TCSC. First, using time simulations, we show that SSR appears and disappears depending on the firing angle of the TCSC. Next, we show that the frequency characteristics vary considerably with the firing angle. Further, we show that SSR occurs in TCSC-compensated systems as well as in conventional series-capacitor-compensated systems when 60 Hz minus the electrical resonance frequency of a transmission system coincides with the torsional oscillation frequency of a generator-turbine shaft. TCSC can avert SSR by changing the firing angle and by shifting the electrical resonance frequency. Next, we propose an equivalent circuit to TCSC which consists of a series capacitor in parallel with a resistor and a reactor. We adjust the parameters so that it shows the same frequency characteristics as TCSC. We apply it to time simulations to see if it is equivalent to TCSC. Finally, we perform an eigenvalue analysis on the equivalent circuit. We obtain results that correspond to the time simulations. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(4): 31–39, 1997     

Slip-line fields for steady-state extrusion through frictionless doubly wedge-shaped dies in plane strain

Slip-line field solutions for steady extrusion through doubly wedge-shaped frictionless die are obtained by assuming a quadrilateral rigid region lying adjacent to the smaller angle wedge surface of the die. Several patterns of the slip-line field are presented. The ranges of the extrusion geometries within which those fields are valid are shown.     

Relative similarity of rotated and reversed figures to the original figures as a function of children's age.

4 rotated and 2 (left-right and up-down) reversed replicas of 11 random figures and a capital letter, F, were ranked for similarity to the originals by 221 4-21 yr old normal children in 7 age groups. For both the random figures and the letter, the left-right reversals were judged as the most similar to the originals at ages 5-7 yrs, while the 45. rotations were judged so at ages 12-19 yrs. The age of 10 was the boundary between these 2 tendencies. Results indicate that young children have already differentiated spatial orientations and directions to a considerable degree but in a different manner from older children and adults. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characteristics of discharge induced by laser-generated plasmas in atmospheric air

The possibility of laser-induced lightning has been investigated for the future application in the protection of electric power systems from lightning strokes. This technique induces lightning strokes artificially along a laser-produced breakdown plasma channel and conducts them to a harmless place on the ground. To clarify the plasma formation mechanism and the discharge (sparkover) induction process, sparkover induction experiments are performed for two types of long-gap electrode configurations, plate-to-rod and plate-to-plate, with a 50-J TEA CO₂ laser. In the present paper, the sparkover voltage characteristics and interferometric measurement on laser-produced plasma mainly are described, together with sparkover induction for a series of metal beads arranged equidistantly which simulate a plasma channel.     

Temporal and spatial trends of organotin contamination in the livers of finless porpoises (Neophocaena phocaenoides) and their association with parasitic infection status

Organotins (OTs) are globally ubiquitous contaminants. Contamination of OTs, particularly butyltins (BTs), has been suspected to cause immunosuppressive effects leading to subsequent infectious diseases or opportunistic infection by pathogens in marine mammals. In the present study, we collected individuals from five different populations of finless porpoises (Neophocaena phocaenoides) from coastal areas of Japan (Seto Inland Sea, Ise Bay, Omura Bay, and Pacific coast) and Hong Kong, and measured OT concentrations in their livers. In addition, infection status of lung nematodes and liver trematodes was also observed to analyze the relationship between OT contamination and parasitic infection in finless porpoises. Hepatic OT concentrations were highest in the Hong Kong population, while levels in the Japanese populations were equivalent to those of other cetaceans from different locations. OT levels in Japan have been decreasing in the past few decades, while OT contamination has shown little improvement in Hong Kong. Observation of parasite infection in Seto Inland Sea porpoises revealed that 16 and 11 out of 22 individuals were infected by lung nematodes and liver trematodes, respectively. Additionally, a significant association between BT levels and parasitic infection status of lung nematodes was detected. Thus, the present study suggests that BTs could be a factor affecting parasitic infection, especially the presence or severity of lung nematodes in finless porpoises. Since chemical exposure may alter the susceptibility of organisms to infectious diseases, the interaction of chemical contamination with infectious diseases needs to be investigated in greater depth to understand the risk of population decline due to these factors in marine mammals.     

On a complete solution for frictionless non-steady state extrusion in plane strain

The slip-line field for frictionless non-steady state extrusion can be constructed by a suitable combination of the slip-line fields for plane strain indentation by smooth and rough dies. The stress state at the vertex of the rigid regions within the slip-line field solution is checked in accordance with Hill's criterion. A statically admissible stress field is constructed by the use of Bishop's method in which some lines of stress discontinuity are introduced. A series method for determining the line of stress discontinuity is proposed by combining Ewing's series method and the method of undetermined coefficients in a power series solution of the differential equation. Some examples of the complete solution are given.     

Effect of surface charges on the polarization of BaTiO3 thin films investigated by UHV‐SPM

Nanostructured BaTiO₃ polar thin films are increasingly critical to the function of future multilayer ceramic capacitors and related oxide‐based electronic devices. The effect of surface charges on BaTiO₃ polarization behavior is therefore investigated by ultra‐high vacuum scanning probe microscopy (UHV‐SPM) for 3 distinct morphologies—epitaxial, polycrystalline, and nanocrystalline films. Regardless of the film morphology, Kelvin probe force microscopy reveals that BaTiO₃ thin film surfaces exhibit positive charging after contact scanning by various noble AFM probes due to the work function difference between tip and specimen. According to piezoresponse force microscopy, these positive charges uniformly stabilize downward polarized domains. However, the hysteresis and concomitant surface charging behavior are strongly sensitive to microstructure and defects. In particular, the stability and switching behavior are influenced by bulk and interfacial defect distributions and hence correlated to film deposition methods and grain size. Such morphology dependent properties for BaTiO₃ films are revealed only through UHV measurements where screening charges from the ambient can be minimized, demonstrating the importance of UHV‐SPM for understanding ferroelectric thin films and nanostructures.     

Independent self-assembly of cadmium-binding {alpha}-fragment of metallothionein in Escherichia coli without participation of {beta}-fragment

We examined the independent self-assembly of the - and ß-fragmentsof human metallothionein (MT) into cadmiumbinding conformationin an Escherichia coli expression system, in addition to wild-typeMT expression. The expressed -fragment formed independentlythe structure of a metal-binding cluster without the aid ofthe ß-fragment. The -fragment and wild-type MT expressedin E.coli were purified and analyzed for their biochemical andspectroscopic properties. The apparent cadmium binding of the-fragment was approximately 12-fold greater than that for thewild-type MT, whereas in other respects the studied biochemicalproperties were similar. In contrast, we were unable to obtainany independently expressed ß-fragment as the cadmium-bindingform in this study. Possible explanations for this phenomenonare discussed.     

A review of studies on the electric field and the current induced in a human body exposed to electromagnetic fields

How high an electric field or current is induced inside a human body when exposed to an electromagnetic field has recently attracted much attention. The background for this is twofold; concern about the possible health effects of electromagnetic fields (usually called ‘EMF issues’), and their positive application to medical treatment or new research subjects. This paper reviews various aspects related to this topic in terms of the following items: basic formulas for field calculation, effect of electromagnetic fields, calculation methods, an Investigation Committee in the IEEJ, and future research subjects. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.