Main Pole Research Articles

Micromagnetic Analysis of Shielded Single-Pole-Type Heads

A micromagnetic analysis of single-pole-type (SPT) heads with side and trailing shields, which are indispensable for obtaining higher values of both track and linear densities, was carried out. First, quasi-static recording field distributions were obtained for various SPT shield structures and compared with those obtained from a static finite element method (FEM) analysis. The recording fields under the main pole were in good agreement, while some discrepancies were found below the shields and the return yoke. Next, time variations of the head field and magnetization processes were obtained for a high-frequency recording current and for various shield structures. Magnetization rotation in the main pole tip, which is the origin of the dynamic recording field, was strongly affected by the magnetization in the side and trailing shields.

Fabrication and Recording Properties of Shielded Planar Type Single Pole Write Head

We fabricated a shielded planar single-pole write head that combined a tapered main pole to obtain a strong write head field and a wraparound shield to obtain a steep head-field distribution. Anisotropy etching pits of Si were used as a template to fabricate the new head, and magnetic yoke material was embedded in the template to form the tapered main-pole tip. As a result, this new head could be fabricated using a novel technique that is different from that used for present recording heads. Our first test recording with the head was successful.

Writing Performance of a Planar Single-Pole Head With a Main Pole Fabricated by Ion-Beam Milling

Writing performance of a shielded planar head with an ion-beam-fabricated main pole was estimated. Magnetic field simulation based on an ion-beam-etched Fe-Co film profile revealed that the two- or three-step-tapered main pole structure, which is one of characteristic configurations of the ion-beam process, has high writing and fabricating potential compared with that of the silicon template process. Especially, the three-step-tapered main pole shows not only high field strength (15 kOe) and field gradient (500 Oe/nm) but also well- suppressed fringing field. The shielded planar head with the ion-beam-milling-processed main pole is one of the leading candidates for application as a writer in the era of Tbpsi recording.

Narrow Track Confinement by AC Field Generation Layer in Microwave Assisted Magnetic Recording

Microwave assisted magnetic recording (MAMR) has been proposed to provide sufficient writability in magnetic recording when the magnetic grain has a large crystalline anisotropy field in high recording density. In this paper, the relationship between the track width and recording head designs in this novel recording scheme is studied using micromagnetic modeling. By controlling the AC field generation layer width, high track density can be obtained without decreasing the main pole width in the writer. A quantitive result shows 770 KTPI can be realized in MAMR with a 120 nm wide main pole and 25 nm wide AC field generation layer.

Micromagnetic Recording Field Analysis of a Single-Pole-Type Head for 1–2 ${\hbox {Tbit/in}}^{2}$

Dynamic recording fields of single-pole-type (SPT) heads, having main pole tip dimensions of 25 times 25 nm at the air bearing surface (ABS), were investigated using a Landau-Lifshitz-Gilbert (LLG) micromagnetic analysis. The recording performance in combination with continuous media and bit-patterned media (BPM) was discussed for areal densities of 1-2 Tbit/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> using the results of LLG micromagnetic media recording simulations. Trailing and side shields were indispensable and the switching speed of the SPT head did not deteriorate on reducing the area of the main pole tip. The advantage of BPM over continuous media was clear with regard to obtaining a higher areal density.

Effect of Sawtooth Shape on Switching Process of Write Head

The static states and reversal processes of write head are studied and compared by two micromagnetic models with sawtooth edges or smooth edges, respectively. In the calculation of magnetostatic interaction with smooth edges, the analytical expression of demagnetization matrix for right-angle triangular prism clusters at hypotenuse has been found. The static domain structures in the main pole tip of both models have a slight difference and differ a little more with higher exchange constant. The switching processes in the two models also have similar behavior, except when the down-track film thickness is less than the pole tip width. Both the exchange field and film thickness affect the ultimate magnetization perpendicular to media and the speed of reversal.

Newly Structured Double Excited Two-Degree-of-Freedom Motor for Security Camera

This paper proposes a newly structured double excited two-degree-of-freedom (DOF) motor with tilt/pan motion to use in a security camera. For applications in active vision, a tilt/pan mechanism should be accurate, fast, small, inexpensive, and have low power requirements. We have designed a new type of motor meeting these requirements, which incorporates both tilt and pan into a single, two-degree-of-freedom device. The focus of the research is to design the improved 2-DOF motor which can eliminate the drawbacks as manufacturing, complicated control, and difficulty in lamination in conventional model. Additionally, to effectively improve the torque characteristic, the main pole pitch and the auxiliary pole shape are determined by the pan motion and the tilt motion, respectively. The validity of proposed structure will be shown in the computer simulation of the newly structured double excited 2-DOF motor for security cameras.

Shielded planar write head

Field calculation with a finite-element method was performed for optimization of the shielded planar head composed of a tapered pole in both down and cross track directions and a wrap-around shield. Especially, effect of the taper angle of the main pole and the gap length and the height of the shield on head field was investigated to obtain a strong head field with a sharp distribution. In order to explore potential of the planar head, comparison with a conventional head with a normal main pole with a short throat was made and feasibility of 1 Tbit/in 2 recording with patterned media was discussed in terms of magnetization reversals of aimed track and thermal stability of magnetization on adjacent tracks.

Micromagnetic modeling for heat-assisted magnetic recording

Heat-assisted magnetic recording (HAMR) is one of the candidate systems beyond the perpendicular recording technology. Here, a micromagnetic model and a heat transfer model are introduced to study the heating and cooling processes in the HAMR media; then, by integration of the SPT head and the laser heating source, the recording performance is simulated and investigated on a single track at an area density of 1 Tb/in 2. In the HAMR system, the temperature in the medium under the laser wave guide is increased by heating, and decreased by air bearing and heat conduction when the write process really occurred. The target of this study is to find the proper design of the head-laser assembly for optimum recording. It is found that the proper distance between the laser wave guide and the head's main pole rear/front edge is only 41.4/1.4 nm for optimum recording performance.

Adjacent track interference analysis of shielded perpendicular writers

In order to achieve high track density in perpendicular recording, write-field leakage from the main pole to adjacent tracks needs to be minimized. We used a 3-D finite-element method to investigate the optimal writer design, which minimizes fringing fields. We also confirmed the results using experimentally by studying adjacent track interference (ATI) on a spinstand. According to both modeling and experimental data, we found that ATI performance can be clearly improved with a wrap-around-shielded (WAS) writer while maintaining enough write-ability. In order to reduce the fringing field, a WAS having thick throat, high permeability and high saturated magnetic flux density was required. We also confirmed that variations of ATI performance due to flare length distributions can be effectively suppressed with the WAS writer.

Prone Retroperitoneoscopy in Treating Complex Renal Vascular Malformations

PURPOSE Two children presented with malignant hypertension. Investigations, including formal angiography, revealed complex renal vascular anomalies; obstruction in upper polar artery in one and arterio-venous malformation in the other. Open surgery and different laparoscopic approaches were considered, but prone retroperitoneoscopy was used in treating both. MATERIAL AND METHODS 1. A 6 year old girl presented with convulsions and malignant hypertension. Captopril DMSA was suggestive of right renal artery stenosis. On formal angiography, the kidney was perfused by what appears to be an arterio-venous malformation. Her blood pressure was very difficult to control on large doses of three antihypertensive agents. There were multiple small collaterals at the lower pole. The right ovarian artery was large and there was a prominent collateral supply originating from it where it crossed the ureter and there were pulsatile vessels along the ureter up to the renal hilum. The kidney was devascularised easily by controlling the main renal pedicle and the ureteric blood vessels prior to nephrectomy. 2. A 14 month old boy presented with six month history of poor appetite, weight loss and irritability. He was severely hypertensive and required 3 antihypertensives. Captopril DMSA showed disappearance of the upper pole of a simplex right kidney. Formal angiography showed acute obstruction of the main upper pole branch. The vessels to the upper pole could be clearly seen and controlled at surgery for partial right nephrectomy. He recovered with no urine leak or bleeding. RESULTS Prone retroperitoneoscopy was used very successfully in treating both. They recovered quickly but stayed longer for gradual withdrawal of antihypertensives. They are remaining well 6 months following surgery. CONCLUSIONS Prone approach provides excellent exposure of the renal blood vessels, aorta and vena cava. Gravity keeps the renal vessels under stretch allowing excellent two-hand dissection.

Magnetospheric accretion on the T Tauri star BP Tauri

From observations collected with the ESPaDOnS and NARVAL spectropolarimeters, we report the detection of Zeeman signatures on the classical T Tauri star BP Tau. Circular polarisation signatures in photospheric lines and in narrow emission lines tracing magnetospheric accretion are monitored throughout most of the rotation cycle of BP Tau at two different epochs in 2006. We observe that rotational modulation dominates the temporal variations of both unpolarised and circularly polarised spectral proxies tracing the photosphere and the footpoints of accretion funnels. From the complete data sets at each epoch, we reconstruct the large-scale magnetic topology and the location of accretion spots at the surface of BP Tau using tomographic imaging. We find that the field of BP Tau involves a 1.2 kG dipole and 1.6 kG octupole, both slightly tilted with respect to the rotation axis. Accretion spots coincide with the two main magnetic poles at high latitudes and overlap with dark photospheric spots; they cover about 2% of the stellar surface. The strong mainly-axisymmetric poloidal field of BP Tau is very reminiscent of magnetic topologies of fully-convective dwarfs. It suggests that magnetic fields of fully-convective cTTSs such as BP Tau are likely not fossil remants, but rather result from vigorous dynamo action operating within the bulk of their convective zones. Preliminary modelling suggests that the magnetosphere of BP Tau extends to distances of at least 4 R* to ensure that accretion spots are located at high latitudes, and is not blown open close to the surface by a putative stellar wind. It apparently succeeds in coupling to the accretion disc as far out as the corotation radius, and could possibly explain the slow rotation of BP Tau.

Evaluation of the Effects of Relationships Between Main Spatial Lower Pole Calyceal Anatomic Factors on the Success of Shock-Wave Lithotripsy in Patients with Lower Pole Kidney Stones

To evaluate the effects of lower pole calyceal anatomy on lower pole stone clearance after shock-wave lithotripsy (SWL). A total of 133 patients who had single lower pole radio-opaque stones treated with SWL alone and who became stone-free or had clinically insignificant residual fragments (CIRF) were included in the study. Pre-shock-wave lithotripsy intravenous urograms were used to determine the lower pole infundibular width and length, lower pole infundibulopelvic (LPIP) angle, caliceal pelvic height (CPH), and lower infundibular length-to-width ratio. In addition, to evaluate the relationship between LPIP and CPH, a more simple alternative measurement instead of LPIP angle, called the parenchyma-to-ureter distance (PUD), was suggested. The correlation between LPIP and PUD was then examined, and a good correlation was found between these values (P <0.000, r = 0.64). The PUD/CPH ratio was also calculated. The stone-free rate was 62%. According to the cutoff points, the lower infundibular length-to-width ratio and PUD/CPH ratio were different in the stone-free and CIRF groups by univariate analysis but not by multivariate analysis. None of the anatomic factors had a statistically significant effect in predicting the success of SWL in patients with lower pole stones. Nevertheless, evaluation of relationships between lower pole anatomic factors may offer some help in reaching a more accurate interpretation of lower pole stone clearance after SWL.

Writer flux closure, transition degradation mechanism, and frequency dependent side track erasure in perpendicular recording

In this second part of the work, the MAGPAR micromagnetic/finite element model was reused to investigate the physics of the write and erase processes in perpendicular recording. The damping constant needed in the Landav–Lifshitz–Gilbert equation was found by applying the Klaassen nonlinear eddy current damped model and set to be 0.1. Previous work highlighted the fact that domains were formed in the soft magnetic underlayer (SUL) under the writer pole in regions where the field opposes the SUL magnetization direction. The domains participate in flux closure and help a more linear response out of the return pole that enhanced fields with an overshoot and opposite polarity relative to the main pole field. These return pole fields could cause adjacent track erasure and MAGPAR was used to study the physics behind it. Particular attention was given to the analysis of frequency or time dependent effects caused by flux delays from the slow moving SUL domains (between the main and return poles). In contrast, fast writing near the main pole was the result of nonlinear flux driven by efficient writers and large currents with overshoot. The writer and SUL used in this work caused a 550ps delay. The delay was analyzed over a range of frequencies between 50 and 1000MHz (i.e., linear densities). The numerical and experimental results showed that this delay played an important role in the erasure process. The strength and location of the return pole erasure fields were affected by the current frequency (i.e., the delay). In particular, the erasure level was substantially reduced at the middle frequencies due to the time match between the current pulses and the domain propagation that influenced flux closure. Return pole field strength increased again at higher frequencies.

A Systemic Approach toward Ecosystem Evolution in Architecture Design

AbstractThe increasing complexity of architectonic procedures demands a re-elaboration of the design methodology, incorporating emerging phenomena of extensive holistic fields. As a human oriented and ecological responsive activity, architecture should target three main poles: adaptation, evolution and regeneration. The operational branches, in which architecture acts, are identified by three complementary non-hierarchical moments: 1)Strategic, referring to an inductive proposition of criteria; structuring procedures; 2)Proto-typical, by making machine models, the dynamic transitions are integrated into procedures of manipulation of inputs and outputs; 3) Testing, advance the notification of expected performances; inform and get informed the adopted systems; calibrate the strategy and the machine behaviors. The parallel coordination of this approach leads to an intelligent programming, which explores scenarios in speculative fields where the action of different forces, elements, programs, negotiations, cooperation, exchanges, etc. are simulated in order to foresee through prototypes the potential evolution, adaptation and regeneration related to specific sites.

Nem tudo brilha na produção de jóias de Limeira - SP

Limeira-SP é uma cidade onde opera um dos principais pólos de produção de jóias e bijuterias, que tem como característica o uso da mão-de-obra informal nos domicílios, nas atividades de montagem, soldagem e cravação de peças. Compreender o funcionamento do setor bem como identificar os riscos à saúde dos trabalhadores são os objetivos do artigo. Foi aplicado um questionário em 22 escolas da Rede Estadual de Ensino. Foi constatado que 27% dos alunos trabalham montando e soldando jóias e bijuterias, uma população de 8.340 indivíduos, dos quais 20% dos estudantes possuem idade abaixo de 17 anos (erro amostral de 5,7%). Os alunos referem queixas de dores em membros superiores, existindo correlação entre trabalhar com jóias e bijuterias e as citadas queixas, indicando a existência de riscos de Lesões por Esforços Repetitivos - LER. Os resultados indicam a necessidade de políticas públicas e esforço da sociedade para regular e encontrar alternativas sustentáveis para o setor.

Géographie historique : itinéraires et organisation spatiale de la Thasos antique

Historical Geography: Routes and Spatial Organization in Ancient Thassos Starting from the translation of the inscription (published in 1964) on the stele indicating Aliki, this paper proposes several possible routes through the island between Aliki and Thassos, running from the East as well as from the West. These hypotheses rely mainly on elements referring to landscape analysis. They reinforce (albeit making it more precise) the hypothesis locating Demetrion in the area of the Kalyvias de Kastro (near Limenaria). Consequently, the spatial organisation of the island that emerges appears as constituted by a centre (the city proper) and relay zones of nucleated habitat loosely disseminated round a main pole structuring a population which was probably quite important from the foundation of the city. The routes described in this paper, as well as the density of the population, indicate that space was secured and exploited more or less intensively in practically the entire territory throughout Antiquity. The richness of the Thassian resources allows us to better understand why the population was so dense from the early days, a population which, in turn, made it possible to make perennial the riches of the island throughout Antiquity.

大学4年生に対する効果的な研究指導法

One year research for forth year students is the most important subject in the engineering faculty. In Kanazawa Institute of Technology, the subject “Engineering DesignIII” , which aims the development of engineer capable of taking actions by their own thought, is set as the main pole of the education. In order to achieve the objectives of this subject, the teachers are required to consider carefully about the setting of research theme and a method of guidance. In this paper, the author′s way of thinking on setting research theme and the practical training method of the engineering design III are described together with the achievements of the students in the author′s laboratory for 9 years.

Relationship between Rotating Sunspots and Flares

Active Region (AR) NOAA 10486 was a super AR in the declining phase of solar cycle 23. Dominated by the rapidly rotating positive polarity of an extensive δ sunspot, it produced several powerful flare-CMEs. We study the evolution and properties of the rotational motion of the major poles of positive polarities and estimate the accumulated helicity injected by them. We also present two homologous flares that occurred in the immediate periphery of the rotating sunspots. The main results are as follows: i) anticlockwise rotational motions are identified in the main poles of positive polarities in the AR; the fastest of them is about 220° for six days. ii) The helicity injection inferred from such rotational motion during the interval from October 25 to 30 is about − 3.0×1043 Mx2, which is comparable that calculated by the local correlation tracking (LCT) method (− 5.2×1043 Mx2) in the whole AR. It is suggested that both methods reveal the essential topological properties of the AR, even if the former includes only the major poles and the fine features of the magnetic field are neglected. iii) It is found that there is a good spatial and temporal correspondence between the onset of two homologous CME-associated flares and the rotational motion of sunspots. This suggests that the rotational motions of sunspots not only relate to the transport of magnetic energy and complexity from the low atmosphere to the corona but may also play a key role in the onset of the homologous flares.

On calculations of the exciting coil of a DC machine

A procedure permitting to calculate a leakage flux of the main pole of a DC machine based on the idea that the DC machine interpolar space can be represented by power tubes of a magnetic flux has been submitted. The procedure permits to increase the calculation accuracy of the DC machine’s exciting coil.