Partial melting of ultrahigh-pressure metamorphic rocks at convergent continental margins: Evidences, melt compositions and physical effects

Ultrahigh-pressure(UHP) metamorphic rocks are distinctive products of crustal deep subduction,and are mainly exposed in continental subduction-collision terranes. UHP slices of continental crust are usually involved in multistage exhumation and partial melting, which has obvious influence on the rheological features of the rocks, and thus significantly affect the dynamic behavior of subducted slices. Moreover,partial melting of UHP rocks have significant influence on element mobility and related isotope behavior within continental subduction zones, which is in turn crucial to chemical differentiation of the continental crust and to crust-mantle interaction.Partial melting can occur before, during or after the peak metamorphism of UHP rocks. Post-peak decompression melting has been better constrained by remelting experiments; however, because of multiple stages of decompression, retrogression and deformation, evidence of former melts in UHP rocks is often erased. Field evidence is among the most reliable criteria to infer partial melting. Glass and nanogranitoid inclusions are generally considered conclusive petrographic evidence. The residual assemblages after melt extraction are also significant to indicate partial melting in some cases. Besides field and petrographic evidence, bulk-rock and zircon trace-element geochemical features are also effective tools for recognizing partial melting of UHP rocks. Phase equilibrium modeling is an important petrological tool that is becoming more and more popular in P-T estimation of the evolution of metamorphic rocks; by taking into account the activity model of silicate melt, it can predict when partial melting occurred if the P-T path of a given rock is provided.UHP silicate melt is commonly leucogranitic and peraluminous in composition with high SiO_2,low MgO, FeO, MnO, TiO_2 and CaO, and variable K_2 O and Na_2 O contents. Mineralogy of nanogranites found in UHP rocks mainly consists of plagioclase + K-feldspar + quartz, plagioclase being commonly albite-rich.Trace element pattern of the melt is characterized by significant enrichment of large ion lithophile elements(LILE), depletion of heavy rare earth elements(HREE) and high field strength elements(HFSE),indicating garnet and rutile stability in the residual assemblage. In eclogites, significant Mg-isotope fractionation occurs between garnet and phengite; therefore, Mg isotopes may become an effective indicator for partial melting of eclogites.

Design of a novel high holding voltage LVTSCR with embedded clamping diode

In order to reduce the latch-up risk of the traditional low-voltage-triggered silicon controlled rectifier(LVTSCR), a novel LVTSCR with embedded clamping diode(DC-LVTSCR) is proposed and verified in a 0.18-μm CMOS process. By embedding a p+implant region into the drain of NMOS in the traditional LVTSCR, a reversed Zener diode is formed by the p+implant region and the n+bridge, which helps to improve the holding voltage and decrease the snapback region.The physical mechanisms of the LVTSCR and DC-LVTSCR are investigated in detail by transmission line pulse(TLP)tests and TCAD simulations. The TLP test results show that, compared with the traditional LVTSCR, the DC-LVTSCR exhibits a higher holding voltage of 6.2 V due to the embedded clamping diode. By further optimizing a key parameter of the DC-LVTSCR, the holding voltage can be effectively increased to 8.7 V. Therefore, the DC-LVTSCR is a promising ESD protection device for circuits with the operation voltage of 5.5–7 V.

Limitation of the Johnson-Mehl-Avrami equation for the kinetic analysis of crystallization in a Ti-based amorphous alloy

The primary crystallization of the Ti40Zr25Ni8Cu9Be18 amorphous alloy was studied by isochronal differential scanning calorimetry(DSC).The activation energy was determined by the Kissinger-Akahira-Sunose method.Trying to analyze the crystallization kinetics of the Ti40Zr25Ni8Cu9Be18 amorphous alloy by two different methods,it was found that the crystallization kinetics did not obey the Johnson-Mehl-Avrami equation.A modified method in consideration of the impingement effect was proposed to perform kinetic analysis of the isochronal crystallization of this alloy.The kinetic parameters were then obtained by the linear fitting method based on the modified kinetic equation.The results show that the isochronal crystallization kinetics of the amorphous Ti40Zr25Ni8Cu9Be18 alloy is heating rate dependent,and the discrepancy between the Johnson-Mehl-Avrami method and the modified method increases with the increase of heating rate.

Design and investigation of novel ultra-high-voltage junction field-effect transistor embedded with NPN

Ultra-high-voltage(UHV)junction field-effect transistors(JFETs)embedded separately with the lateral NPN(JFETLNPN),and the lateral and vertical NPN(JFET-LVNPN),are demonstrated experimentally for improving the electrostatic discharge(ESD)robustness.The ESD characteristics show that both JFET-LNPN and JFET-LVNPN can pass the 5.5-k V human body model(HBM)test.The JFETs embedded with different NPNs have 3.75 times stronger in ESD robustness than the conventional JFET.The failure analysis of the devices is performed with scanning electron microscopy,and the obtained delayer images illustrate that the JFETs embedded with NPN transistors have good voltage endurance capabilities.Finally,the internal physical mechanism of the JFETs embedded with different NPNs is investigated with emission microscopy and Sentaurus simulation,and the results confirm that the JFET-LVNPN has stronger ESD robustness than the JFET-LNPN,because the vertical NPN has a better electron collecting capacity.The JFET-LVNPN is helpful in providing a strong ESD protection and functions for a power device.

Large-Capacity and High-Speed Instruction Cache Based on Divide-by-2 Memory Banks

An increase in the cache capacity is usually accompanied by a decrease in access speed.To balance the capacity and performance of caches,this paper proposes an instruction cache(ICache)architecture based on divide-by-2 memory banks(D2MB-ICache).The control circuit and memory banks of D2MB-ICache work at the central processing unit(CPU)frequency and the divide-by-2 CPU frequency,respectively,so that the capacity of D2MB-ICache can be expanded without lowering its frequency.For sequential access,D2MB-ICache can output the required instruction from memory banks per CPU cycle by dividing the memory banks with a partition mechanism and employing an inversed clock technique.For non-sequential access,D2MB-ICache will fetch certain jump instructions one or two more times,so that it can catch the jump of the request address in time and send the correct instruction to the pipeline.Experimental results show that,compared with conventional ICache,D2MB-ICaches with the same and double capacities show a maximum frequency increase by an average of 14.6%and 6.8%,and a performance improvement by an average of 10.3%and 3.8%,respectively.Moreover,energy efficiency of 64-kB D2MB-ICache is improved by 24.3%.

Steel bar penetrating cervical spinal canal without neurological injury:A case report

BACKGROUND We report a rare case of cervical spinal canal penetrating trauma and review the relevant literatures.CASE SUMMARY A 58-year-old male patient was admitted to the emergency department with a steel bar penetrating the neck,without signs of neurological deficit.Computed tomography(CT)demonstrated that the steel bar had penetrated the cervical spinal canal at the C6–7 level,causing C6 and C7 vertebral body fracture,C6 left lamina fracture,left facet joint fracture,and penetration of the cervical spinal cord.The steel bar was successfully removed through an open surgical procedure by a multidisciplinary team.During the surgery,we found that the cervical vertebra,cervical spinal canal and cervical spinal cord were all severely injured.Postoperative CT demonstrated severe penetration of the cervical spinal canal but the patient returned to a fully functional level without any neurological deficits.CONCLUSION Even with a serious cervical spinal canal penetrating trauma,the patient could resume normal work and life after appropriate treatment.

A multistandard and resource-efficient Viterbi decoder for a multimode communication system

We present a novel standard convolutional symbols generator(SCSG)block for a multi-parameter reconfigurable Viterbi decoder to optimize resource consumption and adaption of multiple parameters.The SCSG block generates all the states and calculates all the possible standard convolutional symbols corresponding to the states using an iterative approach.The architecture of the Viterbi decoder based on the SCSG reduces resource consumption for recalculating the branch metrics and rearranging the correspondence between branch metrics and transition paths.The proposed architecture supports constraint lengths from 3 to 9,code rates of 1/2,1/3,and 1/4,and fully optional polynomials.The proposed Viterbi decoder has been implemented on the Xilinx XC7VX485T device with a high throughput of about 200 Mbps and a low resource consumption of 162k logic gates.