First demonstration of a self-aligned p-channel GaN back gate injection transistor

In this study,we present the development of self-aligned p-channel Ga N back gate injection transistors(SA-BGITs)that exhibit a high ON-state current.This achievement is primarily attributed to the conductivity modulation effect of the 2-D electron gas(2DEG,the back gate)beneath the 2-D hole gas(2DHG)channel.SA-BGITs with a gate length of 1μm have achieved an impressive peak drain current(I_(D,MAX))of 9.9 m A/mm.The fabricated SA-BGITs also possess a threshold voltage of 0.15 V,an exceptionally minimal threshold hysteresis of 0.2 V,a high switching ratio of 10~7,and a reduced ON-resistance(RON)of 548Ω·mm.Additionally,the SA-BGITs exhibit a steep sub-threshold swing(SS)of 173 mV/dec,further highlighting their suitability for integration into Ga N logic circuits.

Recess-free enhancement-mode AlGaN/GaN RF HEMTs on Si substrate

Enhancement-mode(E-mode)GaN-on-Si radio-frequency(RF)high-electron-mobility transistors(HEMTs)were fabri-cated on an ultrathin-barrier(UTB)AlGaN(<6 nm)/GaN heterostructure featuring a naturally depleted 2-D electron gas(2DEG)channel.The fabricated E-mode HEMTs exhibit a relatively high threshold voltage(VTH)of+1.1 V with good uniformity.A maxi-mum current/power gain cut-off frequency(fT/fMAX)of 31.3/99.6 GHz with a power added efficiency(PAE)of 52.47%and an out-put power density(Pout)of 1.0 W/mm at 3.5 GHz were achieved on the fabricated E-mode HEMTs with 1-μm gate and Au-free ohmic contact.

A novel one-time-programmable memory unit based on Schottky-type p-GaN diode

In this work,a novel one-time-programmable memory unit based on a Schottky-type p-GaN diode is proposed.During the programming process,the junction switches from a high-resistance state to a low-resistance state through Schottky junction breakdown,and the state is permanently preserved.The memory unit features a current ratio of more than 10^(3),a read voltage window of 6 V,a programming time of less than 10^(−4)s,a stability of more than 108 read cycles,and a lifetime of far more than 10 years.Besides,the fabrication of the device is fully compatible with commercial Si-based GaN process platforms,which is of great significance for the realization of low-cost read-only memory in all-GaN integration.

Two-dimensional vanadium carbide for simultaneously tailoring the hydrogen sorption thermodynamics and kinetics of magnesium hydride

Magnesium hydride(MgH_(2))is a potential material for solid-state hydrogen storage.However,the thermodynamic and kinetic properties are far from practical application in the current stage.In this work,two-dimensional vanadium carbide(V_(2)C)MXene with layer thickness of 50−100 nm was fist synthesized by selectively HF-etching the Al layers from V_(2)AlC MAX phase and then introduced into MgH_(2) to improve the hydrogen sorption performances of MgH_(2).The onset hydrogen desorption temperature of MgH_(2) with V_(2)C addition is significantly reduced from 318℃ for pure MgH_(2) to 190℃,with a 128℃ reduction of the onset temperature.The MgH_(2)+10 wt%V_(2)C composite can release 6.4 wt%of H_(2) within 10 min at 300℃ and does not loss any capacity for up to 10 cycles.The activation energy for the hydrogen desorption reaction of MgH_(2) with V_(2)C addition was calculated to be 112 kJ mol^(−1) H_(2) by Arrhenius’s equation and 87.6 kJ mol^(−1) H_(2) by Kissinger’s equation.The hydrogen desorption reaction enthalpy of MgH_(2)+10 wt%V_(2)C was estimated by van’t Hoff equation to be 73.6 kJ mol^(−1) H_(2),which is slightly lower than that of the pure MgH_(2)(77.9 kJ mol^(−1) H_(2)).Microstructure studies by XPS,TEM,and SEM showed that V_(2)C acts as an efficient catalyst for the hydrogen desorption reaction of MgH_(2).The first-principles density functional theory(DFT)calculations demonstrated that the bond length of Mg−H can be reduced from 1.71A for pure MgH_(2) to 2.14A for MgH_(2) with V_(2)C addition,which contributes to the destabilization of MgH_(2).This work provides a method to significantly and simultaneously tailor the hydrogen sorption thermodynamics and kinetics of MgH_(2) by two-dimensional MXene materials.

Aluminum hydride for solid-state hydrogen storage:Structure,synthesis, thermodynamics, kinetics, and regeneration

Aluminum hydride(AlH3) is a binary metal hydride that contains more than 10.1 wt% of hydrogen and possesses a high volumetric hydrogen density of 148 kg H2 m^(-3).Pristine AlH3 can readily release hydrogen at a moderate temperature below 200℃.Such high hydrogen density and low desorption temperature make AlH3 one of most promising hydrogen storage media for mobile application.This review covers the research activity on the structures,synthesis,decomposition thermodynamics and kinetics,regeneration and application validation of AlH3 over the past decades.Finally,the future research directions of AlH3 as a hydrogen storage material will be revealed.

Nature of large (Ti, Nb)(C, N) particles precipitated during the solidification of Ti, Nb HSLA steel

To investigate the microsegregation phenomena and complex （Ti, Nb）（C, N） precipitation behavior during continuous casting, a unidirectional solidification unit was employed to simulate the solidification process. The samples of Ti, Nb-addition steels after unidirectional solidification were examined using field emission scanning electron microscope （FE-SEM） and electron probe X-ray microanalyzer （EPMA）. In such specimens, dendrite structure and mushy zone can be detected along the solidification direction. It shows that the addition of titanium, niobium to high-strength low-alloyed （HSLA） steel results in undesirable （Ti, Nb）（C, N） precipitation because of microsegregation. The effect of cooling rate on （Ti, Nb）（C, N） precipitation was investigated. The composition of large precipitates was determined using FE-SEM with EDS. Large （Ti, Nb）（C, N） precipitates could be divided into three kinds according to the composition and morphology. With the cooling rate increasing, Ti-rich （Ti, Nb）（C, N） precipitates are transformed to Nb-rich （Ti, Nb）（C, N） precipitates.

Influence of calcium content on solid ratio of inclusions in Ca-treated liquid steel

It has been found that Ca-treated liquid steel can be cast at a lower superheat. To ascertain the reason for the improved castability of Ca-treated liquid steel and to find the optimal range of calcium content, the behavior of calcium in liquid steel was studied in terms of the relationship between the calcium content and solid ratio of inclusions. The relationship between the calcium content and solid ratio of inclusions was obtained by means of the classification of nonmetallic inclusions in solid and liquid steels at casting temperature according to the Al2O3-CaO-SiO2 phase diagram. The optimum calcium content should be 17-23 ppm.

Thermodynamic calculations and experiments on inclusions to be nucleation sites for intragranular ferrite in Si-Mn-Ti deoxidized steel

Microstructures and inclusions in the Si-Mn-Ti deoxidized steels after cooling in the furnace were investigated. The composition and morphology of the inclusions were analyzed using a field emission scanning electron microscope （FE-SEM） with energy dispersive X-ray spectrometry （EDS）. The kind and composition of the inclusions calculated from the thermodynamic database were in good agreement with the experimental results. There were two main kinds of inclusions formed in the Si-Mn-Ti deoxidized steels. One kind of inclusion was the manganese titanium oxide （Mn-Ti oxide）. Another kind of inclusion was the MnS inclusion with segregation points containing Ti and N. According to the thermodynamic calculation, those segregation points were TiN precipitates. The formation of intragranular ferrite （IGF） microstructures refined the grain size during the austenite-ferrite transformation. The mechanisms of IGF formation were discussed. Mn-Ti oxide inclusions with Mn-depleted zone （MDZ） were effective to be nucleation sites for IGF formation, because the MDZ increased the austenite-ferrite transformation temperature. TiN had the low misfit ratio with IGF, so the TiN precipitated on the MnS surface also promoted the formation of IGF because of decreasing interfacial energies.

Development of a gaseous and solid-state hybrid system for stationary hydrogen energy storage

Hydrogen can serve as a carrier to store renewable energy in large scale.However,hydrogen storage still remains a challenge in the current stage.It is difficult to meet the technical requirements applying the conventional storage of compressed gaseous hydrogen in high-pressure tanks or the solid-state storage of hydrogen in suitable materials.In the present work,a gaseous and solid-state(G-S)hybrid hydrogen storage system with a low working pressure below 5 MPa for a 10 kW hydrogen energy storage experiment platform is developed and validated.A Ti-Mn type hydrogen storage alloy with an effective hydrogen capacity of 1.7 wt%was prepared for the G-S hybrid hydrogen storage system.The G-S hybrid hydrogen storage tank has a high volumetric hydrogen storage density of 40.07 kg H_(2)m^(-3) and stores hydrogen under pressure below5 MPa.It can readily release enough hydrogen at a temperature as low as-15C when the FC system is not fully activated and hot water is not available.The energy storage efficiency of this G-S hybrid hydrogen storage system is calculated to be 86.4%-95.9%when it is combined with an FC system.This work provides a method on how to design a G-S hydrogen storage system based on practical demands and demonstrates that the G-S hybrid hydrogen storage is a promising method for stationary hydrogen storage application.

Fotemustine-based therapy in combination with rituximab as a first-line induction chemotherapy followed by WBRT for newly diagnosed primary central nervous system lymphoma: a prospective phase II trial

Objective:This study aimed to evaluate the safety,efficacy,and feasibility of the rituximab,fotemustine,pemetrexed,and dexamethasone(R-FPD)regimen followed by whole-brain radiotherapy(WBRT)for patients with primary central nervous system lymphoma(PCNSL).Methods:A prospective,single-center phase II clinical trial was conducted.Patients with PCNSL newly diagnosed at the First Affiliated Hospital of Zhengzhou University between July 2018 and July 2020 were studied.The R-FPD regimen consisted of rituximab(375 mg/m2 i.v.on D0),fotemustine(100 mg/m2 i.v.on D1),pemetrexed(600 mg/m2 i.v.on D1),and dexamethasone(40 mg i.v.on D1-5).Patients 60 years or younger who showed a complete response(CR)were treated with 23.4 Gy of WBRT after the end of chemotherapy;those older than 60 years with CR were treated with a wait-and-see approach;and those who did not show CR after the 4th cycle of chemotherapy were given salvage WBRT 30 Gy+local tumor field irradiation up to 45 Gy,regardless of age.Results:A total of 30 patients were included.After 2 cycles,the objective response rate(ORR)was 96.5%(28/29,1 CR,27 PR,0 SD,and 1 PD).After 4 cycles,the ORR was 73.1%(19/26,11 CR,8 PR,4 SD,and 3 PD).After WBRT,the ORR was 90.9%(10/11,7 CR,3 PR,and 1 SD).The grade III and IV toxicity responses were mainly leukopenia(20.0%),thrombocytopenia(23.3%),and anemia(10.0%).Conclusions:Fotemustine-based therapy in combination with rituximab chemotherapy followed by WBRT can improve outcomes,providing ORR benefits and favorable tolerability in patients newly diagnosed with PCNSL.

Instability of parasitic capacitance in T-shape-gate enhancementmode AlGaN/GaN MIS-HEMTs

Parasitic capacitances associated with overhangs of the T-shape-gate enhancement-mode(E-mode)GaN-based power device,were investigated by frequency/voltage-dependent capacitance-voltage and inductive-load switching measurements.The overhang capacitances induce a pinch-off voltage distinguished from that of the E-mode channel capacitance in the gate capacitance and the gatedrain capacitance characteristic curves.Frequency-and voltage-dependent tests confirm the instability caused by the trapping of interface/bulk states in the LPCVD-SiNx passivation dielectric.Circuit-level double pulse measurement also reveals its impact on switching transition for power switching applications.

High-performance enhancement-mode GaN-based p-FETs fabricated with O_(3)-Al_(2)O_(3)/HfO_(2)-stacked gate dielectric

In this letter,an enhancement-mode(E-mode)GaN p-channel field-effect transistor(p-FET)with a high current den-sity of−4.9 mA/mm based on a O_(3)-Al_(2)O_(3)/HfO_(2)(5/15 nm)stacked gate dielectric was demonstrated on a p++-GaN/p-GaN/AlN/AlGaN/AlN/GaN/Si heterostructure.Attributed to the p++-GaN capping layer,a good linear ohmic I−V characteristic fea-turing a low-contact resistivity(ρc)of 1.34×10^(−4)Ω·cm^(2) was obtained.High gate leakage associated with the HfO_(2)high-k gate dielectric was effectively blocked by the 5-nm O_(3)-Al_(2)O_(3)insertion layer grown by atomic layer deposition,contributing to a high ION/IOFF ratio of 6×10^(6)and a remarkably reduced subthreshold swing(SS)in the fabricated p-FETs.The proposed structure is compelling for energy-efficient GaN complementary logic(CL)circuits.

Microstructure of AISI 304 stainless steel strips produced by a twin-roll caster

By optical inspection of macro-etched metallography and electron back-scattered diffraction （EBSD） mapping, this paper analyzed the microstructure of austenitic stainless steel strips produced with an equal-diameter twin-roll strip caster. The results indicate that the microstructure of the strips includes two columnar zones with highly compact dendrites and one equiaxed zone. The characteristics, such as grain size and growing direction of columnar grains and equiaxed grains, were investigated. An additional transitional area with many finer grains between the columnar zone and the equiaxed zone was found. As shown in EBSD analysis, small angle boundaries exist both in the columnar zone and the equiaxed zone, although they are especially more in the transitional area. Additionally, some 〈111〉 twin boundaries were found in the microstructure of the strips.

Investigation of the solute transportation coupled with heat transfer and fluid flow during twin-roll strip casting process

Mathematical model of solute [C] distribution in twin-roll strip casting process has been setup successfully with Calcosoft for the first time. Simulation result shows that in the center of the molten steel pool between the two rolls there is a vortex flow, which is a solute enriched area. But the highest solute concentration position is at the solidification front of the columnar grain zone near the cooling roll surface. Another solute enriched position is in the back flow above the nip point. Combined with the formation mechanism of microstruoture in final as cast strip, analysis shows that solute enriched area is in the transitional area between columnar and equiaxed grain zone.

A new species of the genus Stenochironomus Kieffer(Diptera: Chironomidae) from Xianju National Park,Zhejiang Province, China

Stenochironomus xianjuensis sp. nov. from Xianju National Park, Zhejiang Province, China, is described. The new species is morphologically similar to S. koreanus Borkent, 1984. It can be distinguished from known species in the genus by the following combination of characters： wing with two dark spots surrounding RM and FCu; superior volsella short and small, spatulate, with 4 long setae; inferior volsella elongate, with 3 long setae and a slender terminal spine, posterior margin of tergite IX with 8-10 setae and 8 spines.

Codon Optimization of SMAP-29 Gene and Its Expression in Pichia pastoris

[ Objective] This study aimed to optimize the cedon of antimicrobial peptide SMAP-29 gene and express SMAP-29 in Pichia pastoris. [ Method] Ac- cording to the published amino acid sequence of SMAP-29, a gene encoding SMAP-29 （sheep myeloid antibacterial peptides-29） mature peptide was synthesized and was biased codon usage of Pichia pastoris. The synthesized gene was inserted into Pichia pastoris expression vector pPIC3.5K, transformed into Pichia pastoris strain GSll5 by electmporation, and screened with G418 for high-copy recombinants. The methanol utility plus phenotype （Mut ＋ ） was selected with MM, MD and PCR. The correctly constructed recombinant strain was induced with methanol. Expression of SMAP-29 was analyzed by lysing the induced yeast cells with Tricine- SDS-PAGE. [ Result] After induced with methanol for 2 d, a 3.2 kD induced band was detected in the cell lysate which was consistent to the predicted molecular weight of SMAP-29 ; the expression products purified with gel filtration chromatography showed significant antibacterial effect against Staphyloccocus aureus and Mo- nilia albican but no significant antibacterial effect against Escherichia coli. [ Conclusion] This study laid the foundation for the application of SMAP-29 in biomedi- cine, agriculture and other fields.

Optimization of energy efficiency for the full-duplex massive MIMO systems

The energy efficiency（EE） for the full-duplex massive multi-input multi-output（MIMO） system is investigated. Given the transmit powers of both the uplink and the downlink, the closed-form solutions of the optimal number of antennas and the maximum EE are achieved in the high regime of the signal-to-noise ratio（SNR）. It is shown that the optimal number of antennas and the maximum EE gets larger with the increase in user numbers. To further improve the EE, an optimization algorithm with low complexity is proposed to jointly determine the number of antennas and the transmit powers of both the uplink and the downlink. It is shown that, the proposed algorithm can achieve the system performance very close to the exhaustive search.

Brain regional changes of guanine nucleotide binding protein-inhabitant 2 in acute and chronic morphine-tolerant and-dependent rats

BACKGROUND： Drug addiction involves two main central nervous systems, namely the dopamine and noradrenaline systems. These systems are primarily distributed in five brain regions： the ventral tegmental area, the nucleus accumbens, the prefrontal cortex, the hippocampus, and the locus coeruleus. OBJECTIVE： To investigate regional changes of guanine nucleotide binding protein-inhabitant 2 （Gi2） in dopaminergic and noradrenergic neurons in brains of morphine-tolerant and -dependent rats. DESIGN, TIME, AND SETTING： A randomized control study was performed at the Department of Neurobiology in the Second Military Medical University of Chinese PLA （Shanghai, China） between September 2002 and March 2004. MATERIALS： Thirty-six, healthy, male, Sprague-Dawley （SD） rats were used to establish morphine-dependent models. Morphine hydrochloride was a product of Shenyang First Pharmaceutical Factory （China）; naloxone hydrochloride was a product of Beijing Four-Ring Pharmaceutical Factory （China）; and α subunit of Gi2 antibody was offered by Santa Cruz Biotechnology, lnc （USA）. METHODS： Thirty-six SD rats were randomly divided into six groups （n = 6）： （1） acute morphine-dependent group, （2） acute abstinent group, （3） acute control group, （4） chronic morphine-dependent group, （5） chronic abstinent group, and （6） chronic control group. Rats in the acute morphine-dependent and the acute groups were injected with morphine （5 mg/kg）, one injection every two hours, for a total of eight injections. In the acute and chronic morphine-dependent rat models, morphine withdrawal syndrome was precipitated by an injection of naloxone （5 mg/kg）. Rats in the acute control group were given a peritoneal injection of physiological saline at the same administration time as the above two groups. Rats in the chronic morphine-dependent and chronic abstinent groups were injected with morphine three times per day. The administration dose on day 1 was initially 5 mg/kg at 20：00, which increased by 5 mg/kg at 8：00, 12：00, and 20：00 until day 7. On day 13, the dose continuously increased by 10 mg/kg until a chronic morphine-dependent rat model was successfully induced. Afterwards, the rats presented with withdrawal syndromes on naloxone （5 mg/kg） at 8：00 on the same day. Rats in the chronic control group were injected with physiological saline at the same time of the two chronic groups. MAIN OUTCOME MEASURES： The concentration of Gi2 protein in the five brain regions （ventral tegmental area, nucleus accumbens, prefrontal cortex, locus coeruleus, and hippocampus） was detected by immunohistochemistry. RESULTS： In the acute morphine-dependent and acute abstinent groups, Gi2 protein concentration was significantly decreased in the nucleus accumbens, compared to the acute control group （P 〈 0.01）, while no obvious changes were detected in other brain regions. In the chronic morphine-dependent and chronic abstinent groups, Gi2 protein concentration was significantly decreased in the nucleus accumbens, but significantly increased in the locus coeruleus （P 〈 0.01 ） compared to the chronic control group. CONCLUSION： Morphine dependence and tolerance may induce obvious reductions of Gi2 protein levels in the nucleus accumbens of rats. Chronic morphine dependence desensitizes the homologous neurons.

Low-thermal-budget Au-free ohmic contact to an ultrathin barrier AlGaN/GaN heterostructure utilizing a micro-patterned ohmic recess

A pre-ohmic micro-patterned recess process,is utilized to fabricate Ti/Al/Ti/TiN ohmic contact to an ultrathin-barrier(UTB)AlGaN/GaN heterostructure,featuring a significantly reduced ohmic contact resistivity of 0.56Ω·mm at an alloy temperature of 550℃.The sheet resistances increase with the temperature following a power law with the index of +2.58,while the specific contact resistivity decreases with the temperature.The contact mechanism can be well described by thermionic field emission(TFE).The extracted Schottky barrier height and electron concentration are 0.31 eV and 5.52×10^(18) cm^(−3),which suggests an intimate contact between ohmic metal and the UTB-AlGaN as well as GaN buffer.A good correlation between ohmic transfer length and the micro-pattern size is revealed,though in-depth investigation is needed.A preliminary CMOS-process-compatible metal-insulator-semiconductor high-mobility transistor(MIS-HEMT)was fabricated with the proposed Au-free ohmic contact technique.

运用Cybercity软件CCM模块构建逼真的三维城市模型——Cybercity软件模块和数据库

三维城市模型是城市数据的重要组成部分,瑞士Cybercity运用自己研发的CCM软件生成三维城市模型,内容涉及到数据的类型、比例尺要求、工作步骤及相应的精度,并用实例说明在生产中的实践意义。