Cache sharing among processors is important for Chip Multiprocessors to reduce inter-thread latency, but also brings cache contention, degrading program performance considerably. Recent studies have shown that job co-scheduling can effectively alleviate the contention, but it remains an open question how to efficiently find optimal co-schedules. Solving the question is critical for determining the potential of a co-scheduling system. This paper presents a theoretical analysis of the complexity of co-scheduling, proving its NP-completeness. Furthermore, for a special case when there are two sharers per chip, we propose an algorithm that finds the optimal co-schedules in polynomial time. For more complex cases, we design and evaluate a sequence of approximation algorithms, among which, the hierarchical matching algorithm produces near-optimal schedules and shows good scalability. This study facilitates the evaluation of co-scheduling systems, as well as offers some techniques directly usable in proactive job co-scheduling.
The structure of sputter-deposited Co/Cu multilayer film depends strongly on such preparation conditions as the Ar gas pressure (PAr) and the substrate bias voltage (VB). For films deposited at VB=0 V, the interfaces were flat and the (111) plane orientation was good at low PAr. The (111) orientation was better for ¿30 V films than for 0 V films. The interface was flat at high PAr, in contrast with 0 V films. The giant magnetoresistance (GMR) depended heavily on the layer flatness, the film density, and the existence of crystal grains with an fcc (200) orientation. The effect of annealing on the film structure and GMR was also investigated. Annealing for 10 min. at 200°C in vacuum did not change the film structure very much, but the first GMR peak height of 0 V films decreased significantly, in contrast to the stable second GMR peak.
Ni80Fe20/Cu multilayer films were prepared on glass substrate by magnetron sputtering. The dependence of the magnetoresistance on the thickness of the Cu layer, the thickness of the Ni-Fe layer, the thickness of the buffer layers for Fe, Ni80Fe20 and Cu, and the number of bilayers, was investigated. The MR ratio peaked at dCu= 10Å, where the MR ratio was about 20% at room temperature. When the thickness of the Ni80Fe20 layer was varied, the MR ratio had a broad peak from dNi-Fe=15 to 30Å. The interlayer exchange interaction was evaluated as 3×10¿2 erg/cm2, irrespective of the thickness of the buffer layer. The MR ratio increased with the number of bilayers N, and reached saturation when the total film thickness was about 800 to 1000Å.
NixFe1-x/Cu multilayer films were prepared on glass substrate by magnetron sputtering. The dependence of the giant magnetoresistance on the composition and temperature were investigated. When the composition of the magnetic layer was varied, the MR ratio exhibited peaks at x=0.6 to 0.7 at 4.2K, and at x=0.7 to 0.8 at 300K. As the temperature was raised, the MR ratio of multilayer films with larger magnetic moments decreased more rapidly than that of films with lower magnetic moments. This result can be explained consistently in terms of the spin fluctuation model proposed by Hasegawa.
Co-Cr perpendicular magnetic films were sputter-deposited at extraordinarily high Ar gas pressures above 10 Pa at discharge voltages below 300 V. When films were deposited on glass substrates at Ar gas pressures above 10 Pa, they exhibited columnar structures with large grain sizes and poor crystal orientation, together with large squareness of the in-plane M-H loop. When Ti underlayers with a hig...
We performed analyses of the frequency response of cloth inductors and thin-film inductors using an amorphous core, applying both to miniature dc-dc converters. Because these inductors are used in high-frequency bands from 1 to 100 MHz, the frequency dependence of the inductance L, capacitance C and resistance R in the inductors cannot be disregarded. The undetermined coefficients in a least-squares calculation were found by expressing L, C and R in terms of the coefficients of an expansion in powers of the frequency. In examining the coefficients of the first and second powers of the frequency, the hysteresis loss can be distinguished from the eddy current loss in the inductors. Moreover, the difference between the iron loss and the copper loss can be clarified. The maximum value of the quality factor is obtained at a frequency at which the iron loss is equal to the copper loss. The results calculated using this procedure are in approximate agreement with experiment.
Recent research and development activities related to processing of bulk superconducting oxides are reviewed. Wiring techniques in bismuth and thallium systems are already fairly well developed, allowing critical current densities to meet a required value for application at liquid helium temperature when a certain magnetic field is applied. In yttrium systems, pinning centers have been successfully introduced into the material even at liquid nitrogen temperature as a result of improvements in processing. Some applications utilizing this strong pinning force have been tested. The mechanism for growth of YBa 2 Cu 3 O 7-d from the partially molten state has also gradually been clarified. In all three types of system, it is expected that superconducting wires with high critical current densities at liquid nitrogen temperature will be developed. A recently developed method for growing bulk single crystals is also mentioned briefly.
In this paper, we describe a numerical model of a bridge-connected magnetic circuit for use in the SPICE simulation system. The model was devised on the basis of a bridge-connected magnetic circuit with saturation and hysteresis effects. As an example of application of the SPICE model, we analyzed using a bridge-connected magnetic circuit and a saturable core the transient behavior of a power meas...
In the magneto-inductive effect (MI effect), the inductance L of a ferromagnetic wire element magnetized by an ac current Iac in the wire is changed by an external magnetic field Hex. When the current Iac is passed through the wire, a voltage etot is induced across the wire ends. The voltage has two components: a voltage eR due to RwIac (where Rw is the electrical resistance of the wire), and a vo...
A thin main-pole film is required for high linear densities in perpendicular magnetic recording. In our experiments, Co-Zr-Nb films of thickness 0.08 μm had sufficiently low coercivity, but their domain wall structure nevertheless changed from Bloch walls to cross-tie walls at thicknesses under 0.1 μm. We found that main poles with cross-tie walls had much lower reproduction sensitivity than did t...
The number of domain walls and the domain wall velocity of very thin (110) [001] 3% Si-Fe strip-wound cores were observed by SEM at excitation frequencies up to 5 kHz. Eddy current losses were calculated on the basis of the dynamic domain behavior using two models. a modified Pry and Bean model, and a model which considers the difference between each domain wall velocity. Both models assume sinusoidal domain wall motion. The measured eddy current losses were compared with calculated values. However, the measured losses disagreed with estimations in the frequency range from 50 to 500 Hz. The domain wall motion in each layer was estimated from the flux voltage waveform of a movable pickup coil inserted into a layer of a 3% Si-Fe strip. We found that the voltage waveform was not sinusoidal even if the secondary voltage waveform of the core was sinusoidal, and that the magnitude of the voltage in each layer was not uniform. The results mean that the domain wall motion is not uniform even in the 50 to 500 Hz range. The nonuniformity of the domain wall motion makes the eddy current losses larger than the results estimated on the basis of the two models.
We developed a Mott analyzer of the spherical accelerator type, to measure the spin polarization of electrons extracted from a ferro-magnetic tip or a GaAs sample. This analyzer was designed for a low-acceleration voltage (40 kV). Inelastic scattered electrons are retarded by spherical electrodes. This paper reports the spin polarization of electrons extracted from negative electron affinity (NEA)-GaAs. It was found that this type of Mott analyzer involves a few problems to be solved.
The magnetic properties of ordered bcc FeRh1-xMx alloys (M=Fe, Co, Ni, Pd, Ir and Pt) were studied, and the correlations among the antiferromagnetic-ferromagnetic transition temperature T0, the Curie temperature, magnetization, and lattice constant were investigated. Substitution of the 3d element M for Rh diminishes the transition temperature T0, since the large magnetic moment of the M atom stabilizes the ferromagnetism. Moreover, first-order antiferromagnetic-paramagnetic transition was observed in an FeRh1-xIrx system. The mechanism of those first-order phase transitions can be explained phenomenologically by introducing magneto-volume coupling into the model based on the SCR theory. The ground state properties of FeRh and FeRh1-xPdx are well explained by first-principle band calculations based on the linearized muffin-tin orbital method.
Micro magnetic device simulation studies are reviewed. Flux density distributions and loss analyses are summarized, and the authors' method of analysis using a transmission line model is described. These results are a very significant step toward the establishment of an optimal device design. It is expected that CAD techniques will be established in future.
A bulk Fe 84 Nb 7 B 9 alloy was produced by extruding amorphous powder at temperatures (T e ) between 653 and 723K, at pressures (P e ) between 824 and 1208 MPa, and at a speed (V e ) of 5 mm/s. The subsequent annealing of the extruded bulk alloy for 3.6 ks at temperatures between 873 and 973K resulted in the formation of a (for the most part) single bec phase, with grain sizes near 10 nm. The bulk alloy, extruded at a P e above 1000 MPa, has a high relative density of 99%. The soft magnetic properties are better for bulk materials extruded at lower pressures, and the bulk alloy extruded at T e =698K and P e =870 MPa exhibits a magnetization (B 800 ) of 1.40 T, a permeability of 1123, and a coercive force (H c ) of 47 A/m, values which are inferior to those of the bec ribbon alloy (1.49 T, 22000, 8 A/m). The difference between the soft magnetic properties of the bulk material and the ribbon forms is presumably due to the inhomogeneity of the microstructure, oxidation of the powder, and the remainder of a higher internal stress in the bulk alloy.
The magnetic properties of Nd-(FeCoNiTi)-B and Nd-Fe-B type sintered magnets in thin sheet form were investigated from the standpoint of the deterioration in coercivity caused by machining. It was found that the thickness of a deteriorated layer of an Nd-(FeCoNiTi)-B type magnet is smaller than that of an Nd-Fe-B type magnet. This phenomenon is explained in terms of the toughness and fine-grained structure of Nd-(FeCoNiTi)-B magnets. It is suggested that Nd-(FeCoNiTi)-B magnets may be used in the form of 50 μm thick sheets.
Milking with a conventional milking machine often involves teat trouble, because the pulsation rate of the milking is not variable. A new cylindrical linear oscillatory actuator (CLOA) developed by the authors has a freely variable pulsation rate. This paper analyzes the static and kinetic thrusts of the CLOA. The mover of the CLOA is capable of oscillation at a frequency of 1 Hz with a stroke of ±2 mm, and will be used in new milking machines.
MFM images of a magnetic head and a recording medium, obtained using electrodeposited FeNi, Co and FeCo tips, show quite different features. These differences are explained by the magnetic properties, saturation magnetization and coercive force of the magnetic thin films electrodeposited on the tungsten wires to form the tips. We attempted to observe the magnetic structure of the tip by using magnetostatic bacteria that swim along the lines of the magnetic field originating from the poles on the tip.
The effect of addition of Al to sputtered nanocrystalline Fe-Ta-C films on the film structure, soft magnetic properties and corrosion resistance were investigated. Films were crystallized from an amorphous state to a nanocrystalline state in which ultra-fine TaC particles were dispersed. Most of the Al in the films was dissolved in α-Fe after crystallization. When the Al concentration was increase...
The bec Fe 70 Co 30 alloy has a high saturation magnetization and a large positive magnetostriction, whereas the fcc Ni 75 Co 25 alloy has a large negative magnetostriction value. This paper reports the results of a systematic investigation into the magnetic properties of FeCo/NiCo multilayer films. Magnetostriction in an FeCo/NiCo film becomes smaller as the ratio of the thickness of the NiCo layer to that of the FeCo/NiCo film increases. The film (3/7 nm) has a saturation magnetization of 120 emu/g and a coercivity of 1.7 Oe, with nearly zero magnetostriction.
