您当前的位置:首页 > 论文浏览

按作者

按机构

1. chinaXiv:201804.01458 [pdf]

Comment on ”Integrability of the Rabi Model”

Degang Zhang
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

In this work, I point out that the Braak's solution is a mathematical rather than physical one.

提交时间: 2018-04-12 点击量42下载量23 评论 0

2. chinaXiv:201708.00168 [pdf]

Exact Solution of the Generalized Rabi Model

Degang Zhang
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

The generalized Rabi model is exactly solved by employing the unitary transformation method in the occupation number representation. The analytical expressions for the complete energy spectrum consisting of two sub-energy spectra are presented in the whole range of all the physical parameters. Each energy level possesses twofold degeneracy and is determined by the parameter in the unitary transformation, which obeys a highly nonlinear equation. The corresponding eigenfunction is a convergent infinite series in terms of these physical parameters. Due to the level crossings between the neighboring eigenstates at certain parameter values, such the degeneracies could lead to novel physical phenomena in these quantum systems with the light-matter interaction.

提交时间: 2018-04-12 点击量775下载量333 评论 0

3. chinaXiv:201804.00020 [pdf]

Film-mulched continuous ridge-furrow planting improves soil temperature, nutrient content and enzymatic activity in a winter oilseed rape field, Northwest China

GU, Xiaobo; LI, Yuannong; DU, Yadan
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

Film mulching system is a widely employed agricultural practice worldwide. However, the effects of different planting and mulching patterns on soil nutrient content and enzymatic activity have not been well documented. In this study, we examined the impact of four planting and mulching patterns (including control, flat planting without mulching; M1, flat planting with film mulching; M2, ridge-furrow planting with film mulching on both ridges and furrows; and M3, ridge-furrow planting with film mulching on continuous ridges) on the seed yield of winter oilseed rape, soil moisture, soil temperature, soil organic carbon (SOC) content, soil nutrient content, and soil enzymatic activity over three growing seasons from 2012 to 2015 in a winter oilseed rape field in the semi-arid area of Northwest China. Seed yield of winter oilseed rape, soil moisture, soil temperature, enzymatic activities, and contents of nitrate-nitrogen, available phosphorus, and available potassium were all significantly higher in mulching treatments (M1, M2 and M3) than in control treatment over the three growing seasons, whereas SOC content was significantly lower in mulching treatments than in control treatment during 2013–2014 and 2014–2015. Among the three mulching treatments (M1, M2 and M3), the M3 treatment showed consistently higher seed yield, SOC content, nutrient contents, and enzymatic activities than the other two treatments. Seed yield of winter oilseed rape was 41.1% and 15.0% higher in M3 than in M1 and M2, respectively. SOC content and soil enzymatic activities in the top 0–20 cm soil layers and nitrate-nitrogen content in the top 0–30 cm soil layers were all significantly higher in M3 than in M1 and M2. Therefore, we advise the ridge-furrow planting with film mulching on continuous ridges (i.e., M3) as an efficient planting and mulching pattern for sustainably improving the seed yield of winter oilseed rape and preserving soil fertility in the semi-arid area of Northwest China.

提交时间: 2018-04-03 来自合作期刊:《Journal of Arid Land》 点击量388下载量128 评论 0

4. chinaXiv:201804.00021 [pdf]

Effects of ultraviolet (UV) radiation and litter layer thickness on litter decomposition of two tree species in a semi-arid site of Northeast China

MAO, Bing; ZHAO, Lei; ZHAO, Qiong; ZENG, Dehui
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

Forests and grasslands in arid and semi-arid regions receive high-intensity ultraviolet (UV) radiation year-round. However, how the UV radiation affects the litter decomposition on the forest floor remains unclear. Here, we conducted a field-based experiment in 2011 in the southeastern Horqin Sandy Land, Northeast China, to investigate the effects of UV radiation, litter layer thickness, and their interaction on the mass loss and chemical properties of decomposing litter from Xiaozhuan poplar (Populus × xiaozhuanica) and Mongolian pine (Pinus sylvestris var. mongolica) plantation trees. We found that UV radiation accelerated the decomposition rates of both the Xiaozhuan poplar litter and Mongolian pine litter. For both species, the thick-layered litter had a lower mass loss than the thin-layered litter. The interaction between UV radiation and litter layer thickness significantly affected the litter mass loss of both tree species. However, the effects of UV radiation on the chemical properties of decomposing litter differed between the two species, which may be attributed to the contrasting initial leaf litter chemical properties and morphology. UV radiation mostly had positive effects on the lignin concentration and lignin/N ratio of Xiaozhuan poplar litter, while it had negative effects on the N concentration of Mongolian pine litter. Moreover, litter layer thickness and its interaction with UV radiation showed mostly positive effects on the N concentration and lignin/N ratio of Xiaozhuan poplar litter and the ratios of C/N and lignin/N of Mongolian pine litter, and mostly negative effects on the C/N ratio of Xiaozhuan poplar litter and the N concentration of Mongolian pine litter. Together, these results reveal the important roles played by UV radiation and litter layer thickness in the process of litter decomposition in this semi-arid region, and highlight how changes in the litter layer thickness can exert strong influences on the photodegradation of litter in tree plantations.

提交时间: 2018-04-03 来自合作期刊:《Journal of Arid Land》 点击量304下载量124 评论 0

5. chinaXiv:201804.00022 [pdf]

Hourly and monthly variations in the surface activity patterns of Hemilepistus reaumurii in arid environments of Tunisia

AYARI, Anas ; TOUIHRI, Moez ; GHEMARI, Chedlia; NASRI-AMMAR, Karima
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

Life in desert ecosystems drives animals to adapt their surface locomotor activity according to environmental conditions. In this study, the hourly and monthly variations in the surface activity patterns of the terrestrial crustacean Hemilepistus reaumurii were investigated. The surface activity of H. reaumurii at the population scale was observed by collecting the hourly active individuals from the sunrise to the sunset of the studied day in each month of 2013 in the Bchachma locality, Tunisia. The collected active individuals were put in perspex boxes (on which we labeled the hourly time interval in which the individuals were collected) in the field and then transported to the laboratory for analysis. Individuals were counted, sexed and measured in the laboratory. Despite desert conditions in the studied site, H. reaumurii was characterized by a diurnal surface activity, showing a bimodal pattern during the warm months (i.e., May to October). However, it exhibited a unimodal surface activity pattern in the cold months (i.e., February, March and November). The surface activity was significantly correlated with sunrise and sunset. Moreover, a significant quadratic effect of temperature on the surface activity of H. reaumurii was observed. Furthermore, the study showed that the most important surface activity was recorded in March. The daily exploitation of the temporal niches was significantly different as a function of months. The body size of males were larger than that of females, and the body size of active individuals would change with months. All these behavioural changes in the surface activity represent an adaptive strategy of life in the arid environment.

提交时间: 2018-04-03 来自合作期刊:《Journal of Arid Land》 点击量363下载量113 评论 0

6. chinaXiv:201803.01543 [pdf]

Ultrafine nickel nanoparticles modified reduced graphene oxide as efficient non-platinum catalysts for methanol oxidation

Hongmei Sun; Jun Liu; Zhenfei Tian; Yixing Ye; Changhao Liang
分类: 物理学 >> 交叉学科物理及相关领域的科学与技术

Synthesis of low-cost, highly-active and durable non-platinum metal catalysts for methanol oxidation reaction (MOR) is always full of challenge. Here, Ni nanoparticles modified reduced graphene oxide (Ni/rGO) as an efficient non-platinum catalyst were synthesized by laser ablation of Ni target in graphene oxide (GO) solution and the following in situ reduction process. It found that GO played an important role to restrict the growth and aggregation of ultrafine nickel colloids (< 5 nm) in the process of laser ablation. The resulting Ni/rGO catalyst showed advantageous in active sites and charge transport resulting from the small particle size, uniform dispersion and electronic effect arising from the electron interactions between reduced graphene oxide (rGO) and Ni. The obtained Ni/rGO exhibited the ultrahigh catalytic mass activity of 1600 mA/mg, methanol saturation concentration (4 M), which was superior to that of the reported Ni-based catalysts. Remarkably the mass activities of Ni/rGO before and after 1000 cycles exceed that of the commercial Pt/C catalyst, indicating excellent catalytic activity and stability.

提交时间: 2018-03-30 点击量284下载量126 评论 0

7. chinaXiv:201803.01544 [pdf]

Ni3+ doped cobalt-¬¬nickel layered double hydroxides as high performance electrode material for supercapacitors

Hongmei Sun; Yixing Ye; Zhenfei Tian; Shouliang Wu; Jun Liu
分类: 物理学 >> 交叉学科物理及相关领域的科学与技术

Co-Ni layered double hydroxides (LDHs), as promising supercapacitor electrode materials with high specific capacity, have suffered poor rate property and cycle stability. By doping and topochemical oxidation of Ni ions is considered as efficivent rout to overcome these drawbacks. In this work, Ni3+ doped cobalt-nickel layered double hydroxides (Co-Ni-LDHs) were synthesized by pluse laser ablation of Ni taget in CoCl2 aqeous solution. The existence of Ni3+ ions doped in Co-Ni-LDHs decline the conductive resistance, and increase the mobility of surface charge and transfer rate of electrolyte. As a results, the Ni3+ doped Co-Ni-LDHs display a maximum specific capacitance of 2275 F/g and 1450 F/g at the current density of 1 A/g and 20 A/g, respectivly, indicating a high rate specific capacitance. Moreover, the capacitance retention is to be 80% after 1800 cycles at the current density of 6 A/g, manifesting good cycling stability of Ni3+ doped Co-Ni-LDHs.

提交时间: 2018-03-30 点击量244下载量109 评论 0

8. chinaXiv:201803.01545 [pdf]

Site-specifically Immobilize Pt Nanocrystals on NiFe Layered Double Hydroxide: Old Catalysts with Enhanced Stability Through strong Fe3+-O(H)-Pt Interfacial Contact

Yechuang Han; Pengfei Li; Jun Liu; Shouliang Wu ; Yixing Ye; Zhenfei Tian; Changhao Liang
分类: 物理学 >> 交叉学科物理及相关领域的科学与技术

Agglomeration-triggered deactivation of supported platinum electrocatalysts markedly hinders their application in methanol oxidation reaction (MOR). In this study, graphene-supported nickel–iron layered double hydroxide (NiFe–LDH/rGO), in which Fe3+ was introduced to replace Ni2+ partially in the Ni(OH)2 lattice to provide stronger metal–support bonding sites, was utilized to immobilize Pt nanoparticles (NPs). Given the optimized metal–support interfacial contact (Fe3+–O(H)–Pt) between Pt NPs and NiFe–LDH/rGO nanosheets for Pt/NiFe–LDH/rGO electrocatalysts, the Pt/NiFe–LDH/rGO electrocatalysts displayed dramatically enhanced durability than that of Pt/Ni(OH)2/rGO counterpart as well as commercial Pt/C, and 86.5% of its initial catalytic activity can be maintained even after 1200 cycles of cyclic voltammetry (CV) tests during MOR. First-principle calculations toward the resultant M–O(H)–Pt (M = Fe3+, Ni2+) interfacial structure further corroborates that the NiFe–LDH nanosheets can provide stronger bonding sites (via the Fe3+–O(H)–Pt bonds) to immobilize Pt NPs than those of Ni(OH)2 nanosheets (via the Ni2+–O(H)–Pt bonds).

提交时间: 2018-03-30 点击量212下载量107 评论 0

9. chinaXiv:201803.01547 [pdf]

Thermoelectric performance for SnSe hot-pressed at different temperature

D. Li; J. C. Li; X. Y. Qin; J. Zhang; C. J. Song; L. Wang; H. X. Xin
分类: 物理学 >> 交叉学科物理及相关领域的科学与技术

Herein, nanoparticles SnSe are prepared by fusion method together with ball-milling technique and the effect of hot-pressing temperatures on the thermoelectric properties of the dense materials is explored. Due to the optimization of carrier concentration, the peak figure of merit (ZT) value of the compacted material reaches 0.73 for SnSe sample hot-pressed at 400°C and 450°C. The present investigation indicates that the thermoelectric performance of the SnSe compound can be significantly improved by sintering with suitable temperature.

提交时间: 2018-03-30 点击量241下载量112 评论 0

10. chinaXiv:201803.01548 [pdf]

Optimized thermoelectric properties of AgSbTe2 through adjustment of fabrication parameters

Jian Zhang; Xiaoying Qin; Di Li; Chunjun Song; Yongfei Liu; Hongxing Xin; Tianhua Zou; Yuanyue Li
分类: 物理学 >> 交叉学科物理及相关领域的科学与技术

AgSbTe2 bulk sample is obtained by hot-pressing under different fabrication parameters, and their thermoelectric properties are investigated in the temperature range of 300-550K. The highest ZT=0.86 is achieved at 475K for the sample hot-pressed at 423K and 500MPa due to the lower thermal conductivity and higher power factor. The results indicate that the optimized thermoelectric properties can be obtained for AgSbTe2 compound at the sintering temperature of 423K under the pressure of 500MPa.

提交时间: 2018-03-30 点击量258下载量128 评论 0

12345678910  尾页  转到  [187 页/ 1867 条记录]