Anti-phase domain defects easily form in the in-plane GaAs nanowires(NWs)grown on CMOS-compatiblegroup IV substrates,which makes it difficult to obtain GaAs NWs with a designed length and also leads to asignificant li...Anti-phase domain defects easily form in the in-plane GaAs nanowires(NWs)grown on CMOS-compatiblegroup IV substrates,which makes it difficult to obtain GaAs NWs with a designed length and also leads to asignificant limitation in the growth of high-quality in-plane GaAs NW networks on such substrates.Here,wereport on the selective area growth of anti-phase domain-free in-plane GaAs NWs and NW networks on Ge(111)substrates.Detailed structural studies confirm that the GaAs NW grown using a large pattern period and GaAsNW networks grown by adding the Sb are both high-quality pure zinc-blende single crystals free of stackingfaults,twin defects,and anti-phase domain defects.Room-temperature photoluminescence measurements show asubstantial improvement in crystal quality and good consistency and uniformity of the GaAs NW networks.Ourwork provides useful insights into the controlled growth of high-quality anti-phase domain-defects-free in-planeIII-V NWs and NW networks.展开更多
High performance 1 57μm spotsize converter monolithically integrated DFB is fabricated by the technique of self aligned selective area growth.The upper optical confinement layer and the butt coupled tapered thickn...High performance 1 57μm spotsize converter monolithically integrated DFB is fabricated by the technique of self aligned selective area growth.The upper optical confinement layer and the butt coupled tapered thickness waveguide are regrown simultaneously,which not only offeres the separated optimization of the active region and the integrated spotsize converter,but also reduces the difficulty of the butt joint selective regrowth.The threshold current is as low as 4 4mA.The output power at 49mA is 10 1mW.The side mode suppression ratio (SMSR) is 33 2dB.The vertical and horizontal far field divergence angles are as small as 9° and 15° respectively,the 1dB misalignment tolerance are 3 6μm and 3 4μm.展开更多
CaN nanorods are successfully fabricated by adjusting the flow rate ratio of hydrogen （H2）/nitrogen （N2） and growth temperature of the selective area growth （SAG） method with metal organic chemical vapor deposit...CaN nanorods are successfully fabricated by adjusting the flow rate ratio of hydrogen （H2）/nitrogen （N2） and growth temperature of the selective area growth （SAG） method with metal organic chemical vapor deposition （MOCVD）. The SAG template is obtained by nanospherical-lens photolithography. It is found that increasing the flow rate of 1-12 will change the CaN crystal shape from pyramid to vertical rod, while increasing the growth temperature will reduce the diameters of GaN rods to nanometer scale. Finally the CaN nanorods with smooth lateral surface and relatively good quality are obtained under the condition that the H2：N2 ratio is 1：1 and the growth temperature is 1030℃. The good crystal quality and orientation of GaN nanorods are confirmed by high resolution transmission electron microscopy. The cathodoluminescence spectrum suggests that the crystal and optical quality is also improved with increasing the temperature.展开更多
The selected area electron diffraction （SAED） pattern of magnetic iron oxide core/gold shell nanoparticles has been studied. For the composite particles with mean size less than 10 nm, their SAED pattern is found to...The selected area electron diffraction （SAED） pattern of magnetic iron oxide core/gold shell nanoparticles has been studied. For the composite particles with mean size less than 10 nm, their SAED pattern is found to be different from either the pattern of pure Fe oxide nanoparticles or that of pure Au particles. Based on the fact that the ring diameters of these composite particles fit the characteristic relation for the fcc structure, the Au atoms on surfaces of the concerned particles are supposed to pack in a way more tightly than they usually do in pure Au nanoparticles. The driving force for this is the coherency strain which enables the shell material at the heterostructured interface to adapt the lattice parameters of the core.展开更多
A 32 Gb/s monolithically integrated electroabsorption modulated laser is fabricated by selective area growth technology. The threshold current of the device is below 13mA. The output power exceeds 10mW at 0V bias when...A 32 Gb/s monolithically integrated electroabsorption modulated laser is fabricated by selective area growth technology. The threshold current of the device is below 13mA. The output power exceeds 10mW at 0V bias when the injection current of the distributed feedback laser is 100mA at 25℃. The side mode suppression ratio is over 50 dB. A 32Gb/s eye diagram is measured with a 3.SVpp nonreturn-to-zero pseudorandom modulation signal at -2.3 V bias. A clearly opening eyediagram with a dynamic extinction ratio of 8.01 dB is obtained.展开更多
To improve energy conversion efficiency, optimization of the working fluids in organic Rankine cycles(ORCs) was explored in the range of low-temperature heat sources. The concept of unit-heat-exchange-area(UHEA) net p...To improve energy conversion efficiency, optimization of the working fluids in organic Rankine cycles(ORCs) was explored in the range of low-temperature heat sources. The concept of unit-heat-exchange-area(UHEA) net power, embodying the cost/performance ratio of an ORC system, was proposed as a new indicator to judge the suitability of ORC working fluids on a given condition. The heat exchange area was computed by an improved evaporator model without fixing the minimum temperature difference between working fluid and hot fluid, and the flow pattern transition during heat exchange was also taken into account. The maximum UHEA net powers obtained show that dry organic fluids are more suitable for ORCs than wet organic fluids to recover low-temperature heat. The organic fluid 1-butene is recommended if the inlet temperature of hot fluid is 353.15-363.15 K or443.15-453.15 K, heptane is more suitable at 373.15-423.15 K, and R245 ca is a good option at 483.15-503.15 K.展开更多
A high quality of GaAs crystal growth in nanoscale V-shape trenches on Si（O01） substrates is achieved by using the aspect-ratio trapping method. GaAs thin films are deposited via metal-organic chemical vapor deposit...A high quality of GaAs crystal growth in nanoscale V-shape trenches on Si（O01） substrates is achieved by using the aspect-ratio trapping method. GaAs thin films are deposited via metal-organic chemical vapor deposition by using a two-step growth process. Threading disJocations arising from lattice mismatch are trapped by laterally confining sidewalls, and antiphase domains boundaries are completely restricted by V-groove trenches with Si { 111} facets. Material quality is confirmed by scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and high resolution X-ray diffraction. Low temperature photoluminescence （PL） measurement is used to analyze the thermal strain relaxation in GaAs layers. This approach shows great promise for the realization of high mobility devices or optoelectronie integrated circuits on Si substrates.展开更多
Existing evaluation methods used for the development area selection for commingled production of tight gas and coalbed methane(CBM)are poorly universal and their parameters(e.g.reserves and reservoir physical properti...Existing evaluation methods used for the development area selection for commingled production of tight gas and coalbed methane(CBM)are poorly universal and their parameters(e.g.reserves and reservoir physical properties)cannot reflect the production rate difference during commingled production of tight gas and CBM.In this paper,an integrated evaluation coefficient used for evaluating favorable commingled production areas of tight gas and CBM was defined so as to establish a universal quantitative evaluation index system.Then,by means of orthogonal design together with numerical simulation,the key parameters influencing the commingled production rate and their influence degree on the production rate were determined by taking the commingled production rate as the evaluation target.Finally,a new quantitative evaluation method for the development area selection for commingled production of tight gas and CBM was established.And the following research results were obtained.First,by virtue of the new quantitative evaluation method,the geological occurrence model of tight gas and CBM,the key evaluation parameter and the orthogonal experiment design are established,and the influence degree of evaluation parameters on production rate and the integrated evaluation coefficient of favorable commingled production area of tight gas and CBM are determined.Second,the quantitative evaluation results on the development areas of commingled production of tight gas and CBM in KNW Block based on 12 selected key parameters show that the southern KNW Block and the Well block KNW-37 in the north of KNW Block are the favorable areas for single production of tight gas,Well blocks KNW-10,KNW-33 and KNW-9 are the favorable areas for single production of CBM,and the central and southwestern areas are the favorable areas for the commingled production of tight gas and CBM.In conclusion,this new quantitative evaluation method is universal and can be used as reference for the development area selection for commingled production of tight gas and CBM.展开更多
Transmission electron microscopy (TEM) is a very powerful technique for materials characteriza-tion, providing information relating to morphology, composition, and crystal structure. Selected area diffraction patterns...Transmission electron microscopy (TEM) is a very powerful technique for materials characteriza-tion, providing information relating to morphology, composition, and crystal structure. Selected area diffraction patterns (SADPs) are crystallographic data that can be obtained using a TEM in-strument. Conventional identification through SADP/TEM is tricky and tedious, thereby increasing the difficulty of phase identification. To establish a procedure for phase identification of known and unknown phases, in this study we examined two samples: one, a known phase, was Si with alignment;the other, unknown, was the TixOy phase at the 96.4Au-3Ni-0.6Ti interlayer/ yttria-stabilized zirconia (YSZ) interface of a steel/96.4Au-3Ni-0.6Ti interlayer/YSZ joint. The procedures for phase identification of the known and unknown phases are described herein using a series of SADPs and energy dispersive spectrometry within TEM that would be useful for general researchers.展开更多
Interference control can be realized by selecting the antenna' s electrical and engineering parameters such as gain and radiation pattern, height, azimuth and downtilt to directly influence the field intensity dis...Interference control can be realized by selecting the antenna' s electrical and engineering parameters such as gain and radiation pattern, height, azimuth and downtilt to directly influence the field intensity distribution of radio signals and effectively and reasonably distribute the electro-magnetic energy. This paper discusses how to select an antenna for a densely populated urban area. The discussion is based on the simulation platform of ZTE ' s WCDMA planning system.展开更多
Construction of Silk Road Economic Belt is a giant engine for the economic upgrading of China.Minority areas in Northwest China since then has become a forward position for the opening to the west,which is extremely s...Construction of Silk Road Economic Belt is a giant engine for the economic upgrading of China.Minority areas in Northwest China since then has become a forward position for the opening to the west,which is extremely significant for expanding the hinterland of Chinese economic development,activating economic development in inland and border areas,promoting the open economic development in central and west China,and also forming a new growth pole of Chinese economy.Optimization of industrial selection can promote economic development,constant economic growth of the northwest minority areas and the construction of Silk Road Economic Belt requires the optimization and adjustment of industrial selection,cultivation of competitive industries with market prospects,and formation of new economic growth points.Minority areas in northwest China have a vast territory and abundant resources that are all powerful support for the development of local competitive industries.展开更多
At present,the increase in proved reserves and production of coalbed methane(CBM)in China depends mainly on several CBM bases in the southern Qinshui Basin and in the eastern margin of the Ordos Basin.Therefore,it is ...At present,the increase in proved reserves and production of coalbed methane(CBM)in China depends mainly on several CBM bases in the southern Qinshui Basin and in the eastern margin of the Ordos Basin.Therefore,it is urgent to find new batches of exploration and development strategic replacement areas.For this purpose,we investigated the resources,reservoir properties,preservation conditions,and development conditions of CBM in China,and put forward eight general factors and four critical factors that can be used in establishing selection criteria of strategic replacement areas for affecting the CBM exploration and development in China.The eight general factors are resource abundance,coalbed thickness,gas content,original permeability,burial depth,hydrogeological conditions,coalbed depositional environment,and landforms,and the four critical factors include genetic type,stability type,later reservoir reformation,and damage degree of coal structure.Comparison shows that the low-rank coal area in the northwestern area,the northeastern medium-low rank coal area,and the southwestern medium-high rank and structurally-complex coal area are the major replacement areas for CBM following the northern area of China.Key factors affecting CBM enrichment in each of the three key areas,respectively,are:a)genetic type and stability of coal seams,b)genetic type and reconstruction of the reservoir by volcanic intrusion,and c)stability of coal seams and damage degree of coal structure.Based on these factors,a system for selection and evaluation of strategic replacement areas for CBM development was established.Fifteen blocks in the above three areas were evaluated by using multi-layered fuzzy mathematics,selecting eight favorable areas and seven relatively favorable areas that contain 1.8 trillion m^(3) of predicted CBM geological resources.The eight favorable areas include the Wucaiwan-Dajing coal exploration area in the Zhundong coalfield(eastern Junggar Basin),the Hami-Dananhu mining area in the Turpan-Hami Basin,the Longdong coalfield(eastern Gansu Province),the Yilan and Hegang coalfields in eastern Heilongjiang Province,the Hunchun coalfield in Jilin Province,the southern Sichuan coalfield,and the Shuicheng coalfield in Guizhou Province.These favorable areas were recommended to be the CBM exploration and pilot development target areas in the near future.展开更多
A dust collector is an important equipment in a thermal power plant,and reasonable selection of a dust collector is important for environmental protection in the power plant. Huaneng Xining Power Plant is located at a...A dust collector is an important equipment in a thermal power plant,and reasonable selection of a dust collector is important for environmental protection in the power plant. Huaneng Xining Power Plant is located at an elevation of 2 360 m. Based on the characteristics of the high altitude area and their special requirements for dust collectors,the selection of dust collectors for the thermal power unit in the high altitude area was studied,and then two types of dust collectors( a rotary electrode electrostatic precipitator and electric-bag composite precipitator) for the thermal power unit were compared from the aspects of technological and economical feasibility. Finally,a proposal to select a suitable dust collector for the thermal power plant was put forward.展开更多
Migration characterizations of Ga and In adatoms on the dielectric surface in selective metal organic vapor phase epitaxy （MOVPE） were investigated. In the typical MOVPE environment, the selectivity of growth is pre...Migration characterizations of Ga and In adatoms on the dielectric surface in selective metal organic vapor phase epitaxy （MOVPE） were investigated. In the typical MOVPE environment, the selectivity of growth is preserved for GaN, and the growth rate of GaN micro-pyramids is sensitive to the period of the patterned SiO2 mask. A surface migration induced model was adopted to figure out the effective migration length of Ga adatoms on the dielectric surface. Different from the growth of GaN, the selective area growth of InGaN on the patterned template would induce the deposition of InGaN polycrystalline particles on the patterned Si02 mask with a long period. It was demonstrated with a scanning electron microscope and energy dispersive spectroscopy that the In adatoms exhibit a shorter migration length on the dielectric surface.展开更多
Accordion-shaped traps are widely used in China to catch the Asian paddle crab C harybdis japonica but traps of conventional design often catch juvenile crabs. A new type of accordion-shaped trap with an escape vent(L...Accordion-shaped traps are widely used in China to catch the Asian paddle crab C harybdis japonica but traps of conventional design often catch juvenile crabs. A new type of accordion-shaped trap with an escape vent(L×W=4.3 cm×3.0 cm) was designed and a comparative study between the newly designed and conventional traps was performed in the artifi cial reef area of Zhuwang, Laizhou Bay, China from June to August 2012. The mean catch per unit effort(CPUE) of undersized crabs was signifi cantly lower in the vented traps than in the conventional traps(paired t-test, n =30, P <0.001), while the CPUE of marketable crabs was signifi cantly higher in the vented traps(paired t-test, n =30, P <0.001). The mean size of crabs(carapace length) caught in the vented traps was signifi cantly larger than in conventional traps(paired t-test, n =29, P <0.001). The ratio of undersized crabs was 35.05%±2.57% in conventional traps and 12.53%±0.69% in vented traps(signifi cantly lower, paired t-test, n =29, P <0.001). Therefore, a 4.3 cm×3.0 cm escape vent was considered appropriate for C. japonica fi shing in the artifi cial reef area. This fi nding will assist the development of more sustainable and effi cient crab fi shing methods using accordion-shaped traps.展开更多
Ga N micro-pyramids with AlGaN capping layer are grown by selective metal–organic–vapor phase epitaxy（MOVPE）. Compared with bare Ga N micro-pyramids, AlGaN/Ga N micro-pyramids show wrinkling morphologies at the bo...Ga N micro-pyramids with AlGaN capping layer are grown by selective metal–organic–vapor phase epitaxy（MOVPE）. Compared with bare Ga N micro-pyramids, AlGaN/Ga N micro-pyramids show wrinkling morphologies at the bottom of the structure. The formation of those special morphologies is associated with the spontaneously formed AlGaN polycrystalline particles on the dielectric mask, owing to the much higher bond energy of Al–N than that of Ga–N. When the sizes of the polycrystalline particles are larger than 50 nm, the uniform source supply behavior is disturbed, thereby leading to unsymmetrical surface morphology. Analysis reveals that the scale of surface wrinkling is related to the migration length of Ga adatoms along the AlGaN {1ī01} facet. The migration properties of Al and Ga further affect the distribution of Al composition along the sidewalls, characterized by the μ-PL measurement.展开更多
Selected area grain boundary diffusion(SAGBD)has shown potential in enhancing the coercivity of thick Nd-Fe-B magnets while minimizing the consumption of heavy rare earths.However,the relationships among the SAGBD pro...Selected area grain boundary diffusion(SAGBD)has shown potential in enhancing the coercivity of thick Nd-Fe-B magnets while minimizing the consumption of heavy rare earths.However,the relationships among the SAGBD process,diffusion efficiency,and performance enhancement of the magnets have not yet been well established.Here,different grain boundary diffusion(GBD)approaches were proposed to treat the magnets with different thicknesses using a Tb-Cu alloy diffusion source.The SAGBD was approached with the source diffused from the twelve edge areas of the magnet and from eight vertices of the magnet were called SA-edge and Vertex GBD,respectively.Those diffusing from the edge areas of the four side planes and two c-planes were named SA-ab and SA-c diffusions,respectively.The GBDs from two easy magnetization planes(c-plane)and two parallel planes perpendicular to the c-plane were named c-plane and a-plane diffusions,respectively.It was found that the optimal GBD approaches for the magnets with thicknesses of 5,7.5,10,and 12.5 mm were c-plane,c-plane,SA-edge,and SA-ab diffusions,respectively.Specifically,the SA-ab diffusion shows the highest utilization efficiency of Tb in 12.5 mm-thick magnets,reaching a value of 405.5 kA m-1/wt.%,which is 2.9 and 3.8 times higher than c-plane and SA-c diffusions,respectively.In addition,similar magnetic properties were obtained by c-plane and a-plane diffusions,suggesting that Tb-Cu diffusion does not exhibit significant anisotropic behavior.The microstructure observations and micromagnetic simulations suggest that the reversed domains tend to nucleate at the edges and corners of the magnet.The Vertex diffusion can directly hinder the nucleation and propagation of reversed domains at the corners,but the SA-edge diffusion can effectively postpone their rapid propagation over the entire magnet.This study provides the guidelines for the future development of SAGBD for sintered Nd-Fe-B magnets.展开更多
SiO2,α-Al2O3,γ-Al2O3,ZrO2 and CeO2 were used as supports and Ag as promoter to study their effects on Pd catalysts for selective hydrogenation of acetylene.The catalysts were prepared by impregnated synthesis and ch...SiO2,α-Al2O3,γ-Al2O3,ZrO2 and CeO2 were used as supports and Ag as promoter to study their effects on Pd catalysts for selective hydrogenation of acetylene.The catalysts were prepared by impregnated synthesis and characterized by XRD,BET and TEM.The catalytic reaction was carried out in a fixed-bed reactor.Overall,the low specific surface area supports were better to increase the ethylene selectivity at high conversion rate of acetylene.Among the four Pd catalysts on low specific surface area supports,the catalyst on low specific surface area SiO2(LSA-SiO2) retained a high ethylene selectivity even at complete conversion,while the other catalysts showed significant decrease in the selectivity at complete conversion.The performance of Pd/LSA-SiO2 was important to decrease the loss of ethylene in selective hydrogenation of trace acetylene in ethylene.Addition of Ag to Pd/LSA-SiO2 significantly decreased the formation of ethane,C4 alkenes and green oil,and improved the ethylene selectivity to 90% when Pd:Ag=1:1 and 1:3(ω).When the ratio of Pd to Ag was above 1,the activity of Pd-Ag bimetallic catalyst was similar to that of Pd monometallic catalyst,and the selectivity of ethylene increased with increasing of amount of Ag.When the ratio of Pd to Ag was below 1,the activity of bimetallic catalyst decreased with increasing of amount of Ag,while the selectivity of ethylene was kept unchanged.The optimum temperature was 200-230℃ for 0.02%(ω)Pd-0.02%(ω)Ag/LSA-SiO2 to give a high ethylene selectivity and low formation of green oil.展开更多
On the basis of analyzing the internal logic of rural revitalization and targeted poverty alleviation, it has made a path analysis of the decision-making to overcome poverty and effectively strengthen the rural revita...On the basis of analyzing the internal logic of rural revitalization and targeted poverty alleviation, it has made a path analysis of the decision-making to overcome poverty and effectively strengthen the rural revitalization. Grasping the internal unity of Marxism and the socialist theory system with Chinese characteristics, profoundly expounding the 'comprehensive' rural revitalization and 'concentration'targeted poverty alleviation, 'long-term' rural revitalization and 'stage' targeted poverty alleviation, and'active' rural revitalization Corresponding to the 'passive' targeted poverty alleviation, it corresponds to the philosophical logic of the materialist dialectic, the law of the unity of opposites, the law of mutual change of quality, and the law of negation of negation. It points out the path of targeted poverty alleviation work under the rural revitalization strategy: scientifically compiling the functional spatial planning of poor rural areas;party building leads the transformation of concepts;industrial development is expanding in depth;and public services are advancing to market.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12374459,61974138,and 92065106)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302400)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB0460000)the support from the Youth Innovation Promotion Association,Chinese Academy of Sciences(Grant Nos.2017156 and Y2021043)。
文摘Anti-phase domain defects easily form in the in-plane GaAs nanowires(NWs)grown on CMOS-compatiblegroup IV substrates,which makes it difficult to obtain GaAs NWs with a designed length and also leads to asignificant limitation in the growth of high-quality in-plane GaAs NW networks on such substrates.Here,wereport on the selective area growth of anti-phase domain-free in-plane GaAs NWs and NW networks on Ge(111)substrates.Detailed structural studies confirm that the GaAs NW grown using a large pattern period and GaAsNW networks grown by adding the Sb are both high-quality pure zinc-blende single crystals free of stackingfaults,twin defects,and anti-phase domain defects.Room-temperature photoluminescence measurements show asubstantial improvement in crystal quality and good consistency and uniformity of the GaAs NW networks.Ourwork provides useful insights into the controlled growth of high-quality anti-phase domain-defects-free in-planeIII-V NWs and NW networks.
文摘High performance 1 57μm spotsize converter monolithically integrated DFB is fabricated by the technique of self aligned selective area growth.The upper optical confinement layer and the butt coupled tapered thickness waveguide are regrown simultaneously,which not only offeres the separated optimization of the active region and the integrated spotsize converter,but also reduces the difficulty of the butt joint selective regrowth.The threshold current is as low as 4 4mA.The output power at 49mA is 10 1mW.The side mode suppression ratio (SMSR) is 33 2dB.The vertical and horizontal far field divergence angles are as small as 9° and 15° respectively,the 1dB misalignment tolerance are 3 6μm and 3 4μm.
基金Supported by the Key Program of the National Natural Science Foundation of China under Grant No 61334009the National High Technology Research and Development Program of China under Grant No 2014AA032604
文摘CaN nanorods are successfully fabricated by adjusting the flow rate ratio of hydrogen （H2）/nitrogen （N2） and growth temperature of the selective area growth （SAG） method with metal organic chemical vapor deposition （MOCVD）. The SAG template is obtained by nanospherical-lens photolithography. It is found that increasing the flow rate of 1-12 will change the CaN crystal shape from pyramid to vertical rod, while increasing the growth temperature will reduce the diameters of GaN rods to nanometer scale. Finally the CaN nanorods with smooth lateral surface and relatively good quality are obtained under the condition that the H2：N2 ratio is 1：1 and the growth temperature is 1030℃. The good crystal quality and orientation of GaN nanorods are confirmed by high resolution transmission electron microscopy. The cathodoluminescence spectrum suggests that the crystal and optical quality is also improved with increasing the temperature.
文摘The selected area electron diffraction （SAED） pattern of magnetic iron oxide core/gold shell nanoparticles has been studied. For the composite particles with mean size less than 10 nm, their SAED pattern is found to be different from either the pattern of pure Fe oxide nanoparticles or that of pure Au particles. Based on the fact that the ring diameters of these composite particles fit the characteristic relation for the fcc structure, the Au atoms on surfaces of the concerned particles are supposed to pack in a way more tightly than they usually do in pure Au nanoparticles. The driving force for this is the coherency strain which enables the shell material at the heterostructured interface to adapt the lattice parameters of the core.
基金Supported by the National High-Technology Research and Development Program of China under Grant Nos 2011AA010303and 2012AA012203the National Basic Research Program of China under Grant No 2011CB301702the National Natural Science Foundation of China under Grant Nos 61321063 and 6132010601
文摘A 32 Gb/s monolithically integrated electroabsorption modulated laser is fabricated by selective area growth technology. The threshold current of the device is below 13mA. The output power exceeds 10mW at 0V bias when the injection current of the distributed feedback laser is 100mA at 25℃. The side mode suppression ratio is over 50 dB. A 32Gb/s eye diagram is measured with a 3.SVpp nonreturn-to-zero pseudorandom modulation signal at -2.3 V bias. A clearly opening eyediagram with a dynamic extinction ratio of 8.01 dB is obtained.
基金Projects(U0937604,50876116)supported by the National Natural Science Foundation of ChinaProjects(2010QZZD0107,2014zzts192)supported by the Fundamental Research Funds for the Central Universities of China
文摘To improve energy conversion efficiency, optimization of the working fluids in organic Rankine cycles(ORCs) was explored in the range of low-temperature heat sources. The concept of unit-heat-exchange-area(UHEA) net power, embodying the cost/performance ratio of an ORC system, was proposed as a new indicator to judge the suitability of ORC working fluids on a given condition. The heat exchange area was computed by an improved evaporator model without fixing the minimum temperature difference between working fluid and hot fluid, and the flow pattern transition during heat exchange was also taken into account. The maximum UHEA net powers obtained show that dry organic fluids are more suitable for ORCs than wet organic fluids to recover low-temperature heat. The organic fluid 1-butene is recommended if the inlet temperature of hot fluid is 353.15-363.15 K or443.15-453.15 K, heptane is more suitable at 373.15-423.15 K, and R245 ca is a good option at 483.15-503.15 K.
基金Supported by the National Science and Technology Major Project of China under Grant No 2011ZX02708
文摘A high quality of GaAs crystal growth in nanoscale V-shape trenches on Si（O01） substrates is achieved by using the aspect-ratio trapping method. GaAs thin films are deposited via metal-organic chemical vapor deposition by using a two-step growth process. Threading disJocations arising from lattice mismatch are trapped by laterally confining sidewalls, and antiphase domains boundaries are completely restricted by V-groove trenches with Si { 111} facets. Material quality is confirmed by scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and high resolution X-ray diffraction. Low temperature photoluminescence （PL） measurement is used to analyze the thermal strain relaxation in GaAs layers. This approach shows great promise for the realization of high mobility devices or optoelectronie integrated circuits on Si substrates.
基金supported by the Comprehensive Research Project of CNOOC Research Institute“Overseas Shale Oil and Gas Productivity Evaluation Technology and Method”(No.:YXKY-2016-ZY-03).
文摘Existing evaluation methods used for the development area selection for commingled production of tight gas and coalbed methane(CBM)are poorly universal and their parameters(e.g.reserves and reservoir physical properties)cannot reflect the production rate difference during commingled production of tight gas and CBM.In this paper,an integrated evaluation coefficient used for evaluating favorable commingled production areas of tight gas and CBM was defined so as to establish a universal quantitative evaluation index system.Then,by means of orthogonal design together with numerical simulation,the key parameters influencing the commingled production rate and their influence degree on the production rate were determined by taking the commingled production rate as the evaluation target.Finally,a new quantitative evaluation method for the development area selection for commingled production of tight gas and CBM was established.And the following research results were obtained.First,by virtue of the new quantitative evaluation method,the geological occurrence model of tight gas and CBM,the key evaluation parameter and the orthogonal experiment design are established,and the influence degree of evaluation parameters on production rate and the integrated evaluation coefficient of favorable commingled production area of tight gas and CBM are determined.Second,the quantitative evaluation results on the development areas of commingled production of tight gas and CBM in KNW Block based on 12 selected key parameters show that the southern KNW Block and the Well block KNW-37 in the north of KNW Block are the favorable areas for single production of tight gas,Well blocks KNW-10,KNW-33 and KNW-9 are the favorable areas for single production of CBM,and the central and southwestern areas are the favorable areas for the commingled production of tight gas and CBM.In conclusion,this new quantitative evaluation method is universal and can be used as reference for the development area selection for commingled production of tight gas and CBM.
文摘Transmission electron microscopy (TEM) is a very powerful technique for materials characteriza-tion, providing information relating to morphology, composition, and crystal structure. Selected area diffraction patterns (SADPs) are crystallographic data that can be obtained using a TEM in-strument. Conventional identification through SADP/TEM is tricky and tedious, thereby increasing the difficulty of phase identification. To establish a procedure for phase identification of known and unknown phases, in this study we examined two samples: one, a known phase, was Si with alignment;the other, unknown, was the TixOy phase at the 96.4Au-3Ni-0.6Ti interlayer/ yttria-stabilized zirconia (YSZ) interface of a steel/96.4Au-3Ni-0.6Ti interlayer/YSZ joint. The procedures for phase identification of the known and unknown phases are described herein using a series of SADPs and energy dispersive spectrometry within TEM that would be useful for general researchers.
文摘Interference control can be realized by selecting the antenna' s electrical and engineering parameters such as gain and radiation pattern, height, azimuth and downtilt to directly influence the field intensity distribution of radio signals and effectively and reasonably distribute the electro-magnetic energy. This paper discusses how to select an antenna for a densely populated urban area. The discussion is based on the simulation platform of ZTE ' s WCDMA planning system.
文摘Construction of Silk Road Economic Belt is a giant engine for the economic upgrading of China.Minority areas in Northwest China since then has become a forward position for the opening to the west,which is extremely significant for expanding the hinterland of Chinese economic development,activating economic development in inland and border areas,promoting the open economic development in central and west China,and also forming a new growth pole of Chinese economy.Optimization of industrial selection can promote economic development,constant economic growth of the northwest minority areas and the construction of Silk Road Economic Belt requires the optimization and adjustment of industrial selection,cultivation of competitive industries with market prospects,and formation of new economic growth points.Minority areas in northwest China have a vast territory and abundant resources that are all powerful support for the development of local competitive industries.
基金work has been supported by the China Geological Survey Scientific Research Project 1212011220794the National Science and Technology Major Project 2011ZX 05033-002.
文摘At present,the increase in proved reserves and production of coalbed methane(CBM)in China depends mainly on several CBM bases in the southern Qinshui Basin and in the eastern margin of the Ordos Basin.Therefore,it is urgent to find new batches of exploration and development strategic replacement areas.For this purpose,we investigated the resources,reservoir properties,preservation conditions,and development conditions of CBM in China,and put forward eight general factors and four critical factors that can be used in establishing selection criteria of strategic replacement areas for affecting the CBM exploration and development in China.The eight general factors are resource abundance,coalbed thickness,gas content,original permeability,burial depth,hydrogeological conditions,coalbed depositional environment,and landforms,and the four critical factors include genetic type,stability type,later reservoir reformation,and damage degree of coal structure.Comparison shows that the low-rank coal area in the northwestern area,the northeastern medium-low rank coal area,and the southwestern medium-high rank and structurally-complex coal area are the major replacement areas for CBM following the northern area of China.Key factors affecting CBM enrichment in each of the three key areas,respectively,are:a)genetic type and stability of coal seams,b)genetic type and reconstruction of the reservoir by volcanic intrusion,and c)stability of coal seams and damage degree of coal structure.Based on these factors,a system for selection and evaluation of strategic replacement areas for CBM development was established.Fifteen blocks in the above three areas were evaluated by using multi-layered fuzzy mathematics,selecting eight favorable areas and seven relatively favorable areas that contain 1.8 trillion m^(3) of predicted CBM geological resources.The eight favorable areas include the Wucaiwan-Dajing coal exploration area in the Zhundong coalfield(eastern Junggar Basin),the Hami-Dananhu mining area in the Turpan-Hami Basin,the Longdong coalfield(eastern Gansu Province),the Yilan and Hegang coalfields in eastern Heilongjiang Province,the Hunchun coalfield in Jilin Province,the southern Sichuan coalfield,and the Shuicheng coalfield in Guizhou Province.These favorable areas were recommended to be the CBM exploration and pilot development target areas in the near future.
文摘A dust collector is an important equipment in a thermal power plant,and reasonable selection of a dust collector is important for environmental protection in the power plant. Huaneng Xining Power Plant is located at an elevation of 2 360 m. Based on the characteristics of the high altitude area and their special requirements for dust collectors,the selection of dust collectors for the thermal power unit in the high altitude area was studied,and then two types of dust collectors( a rotary electrode electrostatic precipitator and electric-bag composite precipitator) for the thermal power unit were compared from the aspects of technological and economical feasibility. Finally,a proposal to select a suitable dust collector for the thermal power plant was put forward.
基金supported by the National Natural Science Foundation of China(Grant Nos.61274039 and 51177175)the National Basic Research Program of China(Grant No.2011CB301903)+5 种基金the Ph.D.Programs Foundation of Ministry of Education of China(Grant No.20110171110021)the International Sci.&Tech.Collaboration Program of China(Grant No.2012DFG52260)the International Sci.&Tech.Collaboration Program of Guangdong Province,China(Grant No.2013B051000041)the Science and Technology Plan of Guangdong Province,China(Grant No.2013B010401013)the National High Technology Research and Development Program of China(Grant No.2014AA032606)the Opened Fund of the State Key Laboratory on Integrated Optoelectronics,China(Grant No.IOSKL2014KF17)
文摘Migration characterizations of Ga and In adatoms on the dielectric surface in selective metal organic vapor phase epitaxy （MOVPE） were investigated. In the typical MOVPE environment, the selectivity of growth is preserved for GaN, and the growth rate of GaN micro-pyramids is sensitive to the period of the patterned SiO2 mask. A surface migration induced model was adopted to figure out the effective migration length of Ga adatoms on the dielectric surface. Different from the growth of GaN, the selective area growth of InGaN on the patterned template would induce the deposition of InGaN polycrystalline particles on the patterned Si02 mask with a long period. It was demonstrated with a scanning electron microscope and energy dispersive spectroscopy that the In adatoms exhibit a shorter migration length on the dielectric surface.
基金Supported by the Public Science and Technology Research Funds Projects of Ocean(Nos.201305043,201405010)the National Natural Science Foundation of China(No.41006075)
文摘Accordion-shaped traps are widely used in China to catch the Asian paddle crab C harybdis japonica but traps of conventional design often catch juvenile crabs. A new type of accordion-shaped trap with an escape vent(L×W=4.3 cm×3.0 cm) was designed and a comparative study between the newly designed and conventional traps was performed in the artifi cial reef area of Zhuwang, Laizhou Bay, China from June to August 2012. The mean catch per unit effort(CPUE) of undersized crabs was signifi cantly lower in the vented traps than in the conventional traps(paired t-test, n =30, P <0.001), while the CPUE of marketable crabs was signifi cantly higher in the vented traps(paired t-test, n =30, P <0.001). The mean size of crabs(carapace length) caught in the vented traps was signifi cantly larger than in conventional traps(paired t-test, n =29, P <0.001). The ratio of undersized crabs was 35.05%±2.57% in conventional traps and 12.53%±0.69% in vented traps(signifi cantly lower, paired t-test, n =29, P <0.001). Therefore, a 4.3 cm×3.0 cm escape vent was considered appropriate for C. japonica fi shing in the artifi cial reef area. This fi nding will assist the development of more sustainable and effi cient crab fi shing methods using accordion-shaped traps.
基金supported by the National Natural Science Foundation of China(Grant Nos.61274039 and 61574173)the National Key Research and Development Program,China(Grant No.2016YFB0400105)+9 种基金the International Science and Technology Collaboration Program of Guangdong Province,China(Grant No.2013B051000041)the International Science and Technology Collaboration Program of Guangzhou City,China(Grant No.2016201604030055)the National High Technology Research and Development Program of China(Grant No.2014AA032606)Guangdong Provincial Natural Science Foundation,China(Grant No.2015A030312011)the Science&Technology Plan of Guangdong Province,China(Grant Nos.2015B090903062,2015B010132007,and2015B010129010)the Science and Technology Plan of Guangzhou,China(Grant No.201508010048)the Science and Technology Plan of Foshan,China(Grant No.201603130003)Guangdong–Hong Kong Joint Innovation Project of Guangdong Province,China(Grant No.2014B050505009)the Opened Fund of the State Key Laboratory on Integrated Optoelectronics(Grant No.IOSKL2014KF17)the Zhuhai Key Technology Laboratory of Wide Bandgap Semiconductor Power Electronics,Sun Yat-sen University(Grant No.20167612042080001)
文摘Ga N micro-pyramids with AlGaN capping layer are grown by selective metal–organic–vapor phase epitaxy（MOVPE）. Compared with bare Ga N micro-pyramids, AlGaN/Ga N micro-pyramids show wrinkling morphologies at the bottom of the structure. The formation of those special morphologies is associated with the spontaneously formed AlGaN polycrystalline particles on the dielectric mask, owing to the much higher bond energy of Al–N than that of Ga–N. When the sizes of the polycrystalline particles are larger than 50 nm, the uniform source supply behavior is disturbed, thereby leading to unsymmetrical surface morphology. Analysis reveals that the scale of surface wrinkling is related to the migration length of Ga adatoms along the AlGaN {1ī01} facet. The migration properties of Al and Ga further affect the distribution of Al composition along the sidewalls, characterized by the μ-PL measurement.
基金financially supported by the National Natural Science Foundation of China(No.U21A2052)the Guangxi Science and Technology Program(No.2024AD47008)+1 种基金the Guangdong Basic and Applied Basic Research Foundation(Nos.2022A1515240060 and 2023A1515110100)the China Postdoctoral Science Foundation(No.2023M733642).
文摘Selected area grain boundary diffusion(SAGBD)has shown potential in enhancing the coercivity of thick Nd-Fe-B magnets while minimizing the consumption of heavy rare earths.However,the relationships among the SAGBD process,diffusion efficiency,and performance enhancement of the magnets have not yet been well established.Here,different grain boundary diffusion(GBD)approaches were proposed to treat the magnets with different thicknesses using a Tb-Cu alloy diffusion source.The SAGBD was approached with the source diffused from the twelve edge areas of the magnet and from eight vertices of the magnet were called SA-edge and Vertex GBD,respectively.Those diffusing from the edge areas of the four side planes and two c-planes were named SA-ab and SA-c diffusions,respectively.The GBDs from two easy magnetization planes(c-plane)and two parallel planes perpendicular to the c-plane were named c-plane and a-plane diffusions,respectively.It was found that the optimal GBD approaches for the magnets with thicknesses of 5,7.5,10,and 12.5 mm were c-plane,c-plane,SA-edge,and SA-ab diffusions,respectively.Specifically,the SA-ab diffusion shows the highest utilization efficiency of Tb in 12.5 mm-thick magnets,reaching a value of 405.5 kA m-1/wt.%,which is 2.9 and 3.8 times higher than c-plane and SA-c diffusions,respectively.In addition,similar magnetic properties were obtained by c-plane and a-plane diffusions,suggesting that Tb-Cu diffusion does not exhibit significant anisotropic behavior.The microstructure observations and micromagnetic simulations suggest that the reversed domains tend to nucleate at the edges and corners of the magnet.The Vertex diffusion can directly hinder the nucleation and propagation of reversed domains at the corners,but the SA-edge diffusion can effectively postpone their rapid propagation over the entire magnet.This study provides the guidelines for the future development of SAGBD for sintered Nd-Fe-B magnets.
文摘SiO2,α-Al2O3,γ-Al2O3,ZrO2 and CeO2 were used as supports and Ag as promoter to study their effects on Pd catalysts for selective hydrogenation of acetylene.The catalysts were prepared by impregnated synthesis and characterized by XRD,BET and TEM.The catalytic reaction was carried out in a fixed-bed reactor.Overall,the low specific surface area supports were better to increase the ethylene selectivity at high conversion rate of acetylene.Among the four Pd catalysts on low specific surface area supports,the catalyst on low specific surface area SiO2(LSA-SiO2) retained a high ethylene selectivity even at complete conversion,while the other catalysts showed significant decrease in the selectivity at complete conversion.The performance of Pd/LSA-SiO2 was important to decrease the loss of ethylene in selective hydrogenation of trace acetylene in ethylene.Addition of Ag to Pd/LSA-SiO2 significantly decreased the formation of ethane,C4 alkenes and green oil,and improved the ethylene selectivity to 90% when Pd:Ag=1:1 and 1:3(ω).When the ratio of Pd to Ag was above 1,the activity of Pd-Ag bimetallic catalyst was similar to that of Pd monometallic catalyst,and the selectivity of ethylene increased with increasing of amount of Ag.When the ratio of Pd to Ag was below 1,the activity of bimetallic catalyst decreased with increasing of amount of Ag,while the selectivity of ethylene was kept unchanged.The optimum temperature was 200-230℃ for 0.02%(ω)Pd-0.02%(ω)Ag/LSA-SiO2 to give a high ethylene selectivity and low formation of green oil.
文摘On the basis of analyzing the internal logic of rural revitalization and targeted poverty alleviation, it has made a path analysis of the decision-making to overcome poverty and effectively strengthen the rural revitalization. Grasping the internal unity of Marxism and the socialist theory system with Chinese characteristics, profoundly expounding the 'comprehensive' rural revitalization and 'concentration'targeted poverty alleviation, 'long-term' rural revitalization and 'stage' targeted poverty alleviation, and'active' rural revitalization Corresponding to the 'passive' targeted poverty alleviation, it corresponds to the philosophical logic of the materialist dialectic, the law of the unity of opposites, the law of mutual change of quality, and the law of negation of negation. It points out the path of targeted poverty alleviation work under the rural revitalization strategy: scientifically compiling the functional spatial planning of poor rural areas;party building leads the transformation of concepts;industrial development is expanding in depth;and public services are advancing to market.
