Shield Head Research Articles

Phylogenetic position, complete larval development and larval sexual dimorphism in a rhizocephalan barnacle, Lernaeodiscus rybakovi sp. nov. (Cirripedia: Rhizocephala: Peltogastridae), parasitizing the crab Pachycheles stevensii Stimpson, 1858 (Decapoda: Anomura: Porcellanidae)

Molecular and morphological methods are used to describe Lernaeodiscus rybakovi, a new rhizocephalan species parasitizing the porcellanid crab Pachycheles stevensii Stimpson, 1858, collected in Russian waters of the Sea of Japan. Molecular analysis of three species, including the new one, confirms the monophyly of the genus Lernaeodicus Müller, 1862 and its recent transfer to the family Peltogastridae. The main morphological features of the new species are also common with characters of the other species of the genus Lernaeodiscus Müller, 1862. Externa of L. rybakovi differs from the well studied Lernaeodiscus porcellanae from the E. Pacific by molecular markers, color and the absence of pronounced marginal lobes. Retinacula on the internal cuticle of L. rybakovi are found in the genus Lernaeodiscus for the first time. Some of the female hosts with adult externae were unusual in also carrying their own eggs on the pleopods, a rare situation among rhizocephalans. The complete larval development in the genus Lernaeodiscus is described here for the first time and includes five naupliar and one cypris instar. The main morphological features of Lernaeodiscus nauplii (the presence of flotation collar, morphology of the frontolateral horns and furcal spines, and the arrangement of dorsal setae on the shield head) are common with those of other known peltogastrid larvae, but also resemble nauplii of Peltogasterella in the presence of naupliar eyes and thin structure of the flotation collar. The sizes of male and female cyprids of L. rybakovi overlap slightly. In summer months, larval sex ratio is male-biased. We briefly review important larval characters in the Rhizocephala.

Influence of Tunneling in Cohesionless Soil for Different Tunnel Geometry and Volume Loss under Greenfield Condition

This paper presents the numerical analysis of settlement to profile the vulnerable zone or influence zone due to tunneling activities in cohesionless deposits for free field or Greenfield conditions. The analysis considers the factors like saturated density (γsat), unsaturated density (γunsat), angle of shearing resistance (φ), deformation modulus (ES), volume loss (VL), and the support pressure of the shield head at the tunnel face. The obtained results using a finite element program (FEM) PLAXIS 3D are compared with measured and predicted surface settlement using field measuring instruments, and analytical and empirical solution show a reasonable agreement and are found to be conservative. From literature, for Greenfield condition the ground settlement equal to 10 mm is taken as the minimum value to map the influencing zone considering the fact that the structure which lies beyond this zone would undergo negligible settlement. Settlement trough and 10 mm settlement contour characteristics are presented for different tunnel sizes placed at the same depth and the same tunnel size placed at different depths, respectively. Various influencing zones are arrived for the sandy grounds of different denseness based on the parametrical studies involving parameters such as tunnel size “D,” tunnel axis depth “z,” and volume loss “VL.”

The Ambulatory Eye Shield Head Tracking Device with Real-Time Feedback for Gas Filled Eye Patients.

Gas filled eye surgery is a part of treatment for vitreoretinal diseases such as retinal detachment and macular hole surgery. The patient compliance to maintain the correct position after treatment with gas filling procedure is one of key factor for successful of surgery treatment which helps to restore the vision. The objective of this study is to describe an innovation of eye shield that may improve the positioning compliance for gas filled eye patient and to demonstrate its reliability.The experiment was designed to assess the agreement of the different angles compared to a commercial inclinometer. The angulation was evaluated at 0°, 15°, 30°. 45°, 60°, 75°, 90°, 105°, 120°, 135°, 150°, 165° and 180°. The data analysis shows that the proposed devices have the same measurement as the standard measurement with an Intraclass correlation of >0.99.

Prediction and analysis of surface settlement due to shield tunneling for Xi’an Metro

This study describes a new modified prediction method of surface settlement (SS) for Xi’an Metro. The estimation method of SS and its characteristic parameters, volume loss (VL), maximal SS, and settlement trough width (STW) are reviewed and discussed in this paper. The gap parameter (GP) is applied to estimate VL; however, the calculation method of GP and its influence factors have not been clarified entirely. In this study, six influence factors are introduced into the new GP model, and the detailed solutions are presented. This estimation method is able to take into account the support pressure of the shield head at the tunnel face, the lining support pressure around the tunnel opening, the filling effect of tail grouting, yawing, and pitching of the shielding machine, and the long-term deformation of the remoulded surrounding soil. Based on Xi’an Metro line 2, the soil behaviors and measured SS characteristics are deeply investigated. The upper and lower bounds of the total GP of the 15 cases are predicted. Comparison of the predicted SS troughs with field observations can show reasonable agreement. It is suggested that the new estimation method can be used effectively in estimating the SS induced by the shield tunneling method.

Study of High Track Density in Tape Storage

This paper addresses the effect of a shield for the ring head to improve high track density. We analyzed the shape and the position of the shield with the finite-element method and checked the effect of the shield using a three-dimensional magnetic recording simulator in which a curing magnetic reversal model and self-consistent magnetic calculations were combined with the finite-element method. In this analysis, all components of the fringing field of the shield head were reduced, especially for the 30-degree components, which refers to the orientation angle of obliquely oriented metal evaporated tapes. We calculated the side erase band (SEB) from recorded magnetization on DC erased obliquely oriented metal evaporated tapes and found an optimal shield shape and position with respect to the head/media spacing. The well designed shield head was advantageous in having an SEB that was less than half that of a conventional head, was effective for achieving high track density in a tape storage system.

Analysis of Track-Edge Noise From the Viewpoint of Write Heads With Different Dimensions

Track-edge noise, which is one of the major hindrances in achieving the narrow track recording, was studied through spinstand testing and micromagnetics simulations. Three heads with different write pole widths were carefully chosen in the experiments so that their on-track head field gradients were almost similar, and the recording performance of these heads was evaluated with an identical narrow read head. Despite of their similar on-track field gradients, the narrowest write head exhibited a significantly low signal-to-noise ratio (SNR) at the track center. The reason for this is that the skirt of the reader sensitivity function contributed to an increase in noise even when the reader was at the center of the track. This experimentally observed track-edge noise effect on the on-track SNR was also confirmed through the micromagnetics simulations. The simulation results revealed that increasing the cross-track head field gradient effectively reduces the track-edge noise. A wraparound shield head is one of the promising candidates for narrow track recording because of its high cross-track head field gradient.

New Type Side Shield Head for Ultrahigh Density Recording

In magnetic writing heads, one of the most important factors for ultrahigh recording density is the skirt width of write field along cross track direction without degradation of head field and field gradient. The side shield design is known to be the most powerful design for reducing the skirt width. However, the side shields make write field and field gradient weak. By FEA simulation, we propose the shell type side shield to reduce skirt width without field degradation. As a result, we could reduce track width from 255 to 190 nm with no head field degradation, at 7060 Oe. We used design of experiment (DOE) tools, especially response surface method (RSM), to optimize the design. In the simulation, we took into account all soft magnetic materials (write head and soft magnetic underlayer). To verify the results, we checked the correlation between the head field of each shape and ATE.

Trailing Shield Head Recording in Discrete Track Media

Magnetic recording in perpendicular media using write heads with trailing shields was simulated. The recording performance of discrete track media and continuous media was compared. Trailing shields increase the head field gradient, leading to sharper transitions and higher signal-to-noise ratio (SNR). The optimum trailing shield gap was determined to be 30 nm for both types of media. Using such a write head and subject to the condition of no adjacent track erasure the discrete track media SNR was 1.5 dB higher than the continuous media at a linear density of 1700 kfci

高抵抗シールド膜を用いた狭ギャップ再生ヘッド

A narrow-gap read head with a high-resistance magnetic film was investigated. The film has a resistance of more than 10 m Ω cm and good soft magnetic properties. The high-resistance shield head comprises a GMR film, insulator films for the read-gap, high-resistance magnetic films, insulator films to prevent breakdown of the head, and magnetic shield films. The fabricated high-resistance shield head shows a good output waveform. However, it has a slightly larger half-amplitude pulse width (PW50) value than a conventional shield head, because the permeability of the high-resistance magnetic film is insufficiently high. We concluded that a read head using a high-resistance shield with high permeability would be a suitable candidate for a narrow-gap read head.