C.W. Chang

A 7mW-to-183mW Dynamic Quality-Scalable H.264 Video Encoder Chip

A dynamic quality-scalable H.264 video encoder is presented for power-adaptive video encoding. In 0.13mum CMOS technology, it requires 470kgates/13.3kB SRAM and consumes 7mW/183mW in encoding 30fps CIF/HD720 video. Compared to the state-of-the-art design for real-time HD720 video encoding, a 49% reduction in gate count and a 61% reduction in internal memory is achieved

Magnetic properties, phase evolution, and microstructure of melt spun SmCo7-xHfxCy (x=0-0.5; y=0-0.14) ribbons

Magnetic properties, phase evolution, and microstructure of melt spun SmCo7−xHfxCy (x=0–0.5; y=0–0.14) ribbons via direct quenching have been investigated. For SmCo7−xHfx series ribbons, proper volume fraction of Hf is effective to stabilize and increase the magnetocrystalline anisotropy field of the TbCu7-type structure. Accordingly, the optimal magnetic properties of Br=6.4kG, Hci=7.3kOe, and (BH)max=8.7MGOe could be obtained for x=0.1. Furthermore, a slight C addition to above alloys is helpful in refining the grain size of the ribbons from 100–400nm for C-free to 10–80nm for C-containing samples. As a result, the magnetic properties are further improved to Br=6.9kG, Hci=11.8kOe, and (BH)max=10.6MGOe for SmCo6.8Hf0.2C0.12 nanocomposite ribbons.

A Condition-based Intra Prediction Algorithm for H.264/AVC

This paper proposes a condition-based algorithm for H.264/AVC 4times4 intra prediction. Exploiting high correlation existed in neighboring intra prediction modes, we propose the three conditions to skip the less possible candidates in doing intra4times4 block mode decision. When compared to the 9 prediction modes in the full search algorithm, the proposed algorithm can complete a 4times4 intra prediction using 4.4 prediction modes operation in average. The simulation result shows that the proposed algorithm can reduce computational complexity up to 44% at the cost of less than 0.1 dB PSNR loss in average

A Quality Scalable H.264/AVC Baseline Intra Encoder for High Definition Video Applicaitons

In this paper, we propose a quality scalable H.264/AVC baseline intra encoder with two hardware sharing mechanisms and three timing optimizing schemes. The proposed hardware sharing schemes share the common terms among intra prediction of different modes to reduce the hardware cost. The proposed timing optimizing schemes are used to improve the data throughput rate. The proposed design supports different clock rates of 26/33/47 MHz and 70/85 MHz to encode SD and HD720 video sequences with 30fps respectively with different qualities. According to a 0.13¿m CMOS technology, the proposed design costs 170K gates and 4.43 KB of internal SRAM at clock rate of 130MHz.

Magnetic properties and microstructure of directly quenched Nd9.5Fe75.5−xMxB15 (M=Mo, Nb, Ta, Ti, V, and Zr; x=0–4) bulk magnets

Magnetic properties and microstructure of directly quenched Nd9.5Fe75.5−xMxB15 (M=Mo, Nb, Ta, Ti, V, and Zr; x=0–4) bulk magnets in rod form with a diameter of 0.7mm have been studied. The substitution of the selected refractory elements for Fe in the Nd9.5Fe75.5MxB15 alloy can suppress the formation of the soft phases, including Nd2Fe23B3 and one unknown phase, leading to the presence of a large amount of the Nd2Fe14B phase. Besides, the grain size at the core side of the rods is refined from a micrometer scale for a ternary magnet to 50–120nm for the magnets with refractory element substitution. As a result, the magnetic properties are improved remarkably from Br=5.0kG, Hci=1.0kOe, and (BH)max=1.7MGOe for a ternary magnet to Br=5.7–6.5kG, Hci=2.0–14.6kOe, and (BH)max=3.1–8.7MGOe for refractory element substituted magnets. The optimal magnetic properties of Br=6.5kG, Hci=10.3kOe, and (BH)max=8.7MGOe can be achieved in the Nd9.5Fe72.5Ti3B15 magnet, while the highest coercivity of Hci=14.6kOe, with Br=5.9k...

Microstructure and magnetocaloric effect of melt-spun Y2Fe17 ribbons

The phase constitution, microstructure, and magnetocaloric effect (MCE) in low-cost iron-based binary Y2Fe17 ribbons have been investigated by using x-ray diffraction, transmission electron microscopy, and measuring their magnetic properties, respectively. It is found that the crystal structure of the as-spun ribbons is hexagonal Th2Ni17 type with the wheel speed ranging from 10to40m∕s because of the week glass-forming ability. The ribbon prepared at 20m∕s shows a magnetic entropy change of 1.89J∕kgK under magnetic field change of 10kOe. The low-cost, easy-synthesis, and considerable MCE properties make Y2Fe17 alloys in ribbon form as suitable room temperature MCE materials.

Magnetic properties, phase evolution, and microstructure of melt-spun (Sm1−xPrx)Co7−yHfyCz (x=0–1; y=0.1–0.3; z=0–0.14) ribbons

Magnetic properties, phase evolution, and microstructure of melt-spun (Sm1−xPrx)Co7−yHfyCz ribbons have been investigated. For (Sm1−xPrx)Co7−yHfy (x=0–1; y=0.1–0.3) ribbons, the magnetization increases, but coercivity decreases, with increasing Pr content. However, the phase constitution and microstructure have not been influenced by modifying Pr content x. The attractive magnetic properties of Br=6.5kG, Hci=6.1kOe, and (BH)max=7.2MGOe could be obtained for (Sm0.8Pr0.2)Co6.9Hf0.1 ribbons. A slight addition of C in (Sm0.8Pr0.2)Co6.9Hf0.1Cz (z=0.06–0.14) ribbon not only refines the microstructure, but also induces nanoscale fcc-Co precipitation in the matrix, leading to the stronger exchange-coupling effect between magnetic grains and the enhancement of remanence and magnetic energy product. As a result, the improved magnetic properties of Br=7.1kOe, Hci=8.5kOe, and (BH)max=11.2MGOe can be achieved for (Sm0.8Pr0.2)Co6.9Hf0.1C0.12 ribbons.

Magnetic properties, microstructure and phase evolution of (Ce1−xPrx)9.5Febal.CoyTi2B10 (x=0–1 and y=0, 2.5) nanocomposites

Magnetic properties, microstructure, and phase evolution of (Ce1−xPrx)9.5Febal.CoyTi2B10 (x=0–1 and y=0, 2.5) nanocomposites have been investigated. A progressive substitution of Pr for Ce enhances the remanence (Br), intrinsic coercivity (Hci), and maximum energy product [(BH)max] of the ribbons effectively. In addition, the Curie temperature of 2:14:1 phase also increases with increasing Pr concentration. For Co-free (Ce1−xPrx)9.5Febal.Ti2B10 ribbons, magnetically hard 2:14:1 phase and two soft phases, α-Fe and Fe3B, are found in the ribbons with x=0, 0.3, 0.4, and 0.7, while Fe3B phase disappears in the ribbons with x=1. On the other hand, the value of Br, (BH)max, temperature coefficient α, and Curie temperature of 2:14:1 and α-Fe are improved with a slight substitution of 2.5 at. % Co for Fe. The magnetic properties of Br=8.5kG, Hci=7.5kOe, (BH)max=13.5MGOe, α=−0.185%∕°C, and β=−0.54%∕°C can be achieved in (Ce0.5Pr0.5)9.5Febal.Co2.5Ti2B10 nanocomposites.

Coercivity enhancement of melt spun FePt ribbons by Au addition

The effect of Au content on the magnetic properties and microstructure of melt spun (FePt)100−xAux (x=0–40) ribbons have been investigated. X-ray diffraction and thermal magnetic analysis results indicate that Au-rich phase coexists with ordered L10-FePt(Au) phase in ternary FePtAu ribbons after an isothermal annealing. Meanwhile, the Curie temperature of L10-FePt(Au) phase in annealed (FePt)100−xAux (x=0–40) ribbons is almost unchanged, revealing that higher volume fraction of Au addition does not modify the composition of the L10-FePt(Au) phase. All the Au containing ribbons exhibit a completely isolated L10-FePt(Au) granular structure, and the grain size is effectively decreased with the increase of Au content. As a result, the intrinsic coercivity (Hci) of the ribbons increases substantially from 2.1kOe for binary FePt to 19.5kOe for (FePt)60Au40.

Effect of B content on the magnetic properties, phase evolution, and aftereffect of nanocrystalline FeCoPtB ribbons

Effect of B content on the magnetic properties, phase evolution, magnetic after effect, and the activation energy (Ea) for the melt-spun [(Fe0.7Co0.3)0.725Pt0.275]100−xBx (x=14–18) ribbons has been investigated. Sufficient amount of boron addition effectively decreases the activation energy of ordering transformation, and also refines the grain size of the studied ribbons after thermal annealing, resulting in the improvement of Hic from 3.4 kOe for x=14 to 6.2 kOe for x=18. The highest permanent magnetic properties of Br=10.1 kG, Hic=5.4 kOe, and (BH)max=15.7 MGOe can be achieved in [(Fe0.7Co0.3)0.725Pt0.275]85B15 ribbons. Meanwhile, the magnetic after effect study evidences that the activation volume is reduced with the increase in B content from V=41.33×10−19 cm3 for x=14 to V=21.71×10−19 cm3 for x=18, arisen from the lower volume fraction of magnetically soft phases and the stronger exchange-coupling effect between magnetic grains.