分类: 地球科学 >> 地理学 提交时间: 2021-06-04 合作期刊: 《干旱区科学》
摘要: The soil type is a key factor influencing N (nitrogen) cycling in soil; however, gross N transformations and N2O emission sources are still poorly understood. In this study, a laboratory 15N tracing experiment was carried out at 60% WHC (water holding capacity) and 25ºC to evaluate the gross N transformation rates and N2O emission pathways in sandy loam and silt loam soils in a semi-arid region of Heilongjiang Province, China. The results showed that the gross rates of N mineralization, immobilization, and nitrification were 3.60, 1.90, and 5.63 mg N/(kg•d) in silt loam soil, respectively, which were 3.62, 4.26, and 3.13 times those in sandy loam soil, respectively. The ratios of the gross nitrification rate to the ammonium immobilization rate (n/ia) in sandy loam soil and silt loam soil were all higher than 1.00, whereas the n/ia in sandy loam soil (4.36) was significantly higher than that in silt loam soil (3.08). This result indicated that the ability of sandy loam soil to release and conserve the available N was relatively poor in comparison with silt loam soil, and the relatively strong nitrification rate compared to the immobilization rate may lead to N loss through NO3– leaching. Under aerobic conditions, both nitrification and denitrification made contributions to N2O emissions. Nitrification was the dominant pathway leading to N2O production in soils and was responsible for 82.0% of the total emitted N2O in sandy loam soil, which was significantly higher than that in silt loam soil (71.7%). However, the average contribution of denitrification to total N2O production in sandy loam soil was 17.9%, which was significantly lower than that in silt loam soil (28.3%). These results are valuable for developing reasonable fertilization management and proposing effective greenhouse gas mitigation strategies in different soil types in semiarid regions.
分类: 动力与电气工程 >> 工程热物理学 提交时间: 2017-06-22 合作期刊: 《热科学学报》
摘要: Pipes are widely used to transport gas, oil and water in industries. Drag reduction in pipes is an increasingly concerned problem to save energy. Some researches have indicated that the non-smooth surface with special structures can reduce flow loss. In this paper, an experimental investigation has been performed on the effects of a kind of surface groove on the drag in both rectangular and circular duct at different Reynolds numbers. In the experiment of the rectangular duct, total pressure at both inlet and outlet were measured. Static pressure on the wall was measured on the surface with smooth and grooved film respectively. In the circular duct, a boundary layer pressure probe was used to measure the total pressure distribution at both inlet and outlet. Four taps at inlet and outlet were used to measure static pressure. The loss coefficient is used to evaluate the effects of the surface groove on drag reduction. The experiment was conducted with the Reynolds number range from 1.28x10(4) to 2.57x10(4). The result shows a maximum drag loss reduction of approximately 2.4% in rectangular duct at Reynolds number of 2.4x10(4). A 10% reduction of pipe pressure loss by grooved surface is measured in circular duct at a Reynolds number of 3.0x10(5).
分类: 天文学 >> 天文学 提交时间: 2024-03-29 合作期刊: 《Research in Astronomy and Astrophysics》
摘要: Strangeon stars, which are proposed to describe the nature of pulsar-like compact stars, have passed various observational tests. The maximum mass of a non-rotating strangeon star could be high, which implies that the remnants of binary strangeon star mergers could even be long-lived massive strangeon stars. We study rigidly rotating strangeon stars in the slowly rotating approximation, using the Lennard-Jones model for the equation of state. Rotation can significantly increase the maximum mass of strangeon stars with unchanged baryon numbers, enlarging the mass-range of long-lived strangeon stars. During spin-down after merger, the decrease of radius of the remnant will lead to the release of gravitational energy. Taking into account the efficiency of converting the gravitational energy luminosity to the observed X-ray luminosity, we find that the gravitational energy could provide an alternative energy source for the plateau emission of X-ray afterglow. The fitting results of X-ray plateau emission of some short gamma-ray bursts suggest that the magnetic dipole field strength of the remnants can be much smaller than that of expected when the plateau emission is powered only by spin-down luminosity of magnetars.
分类: 核科学技术 >> 核材料与工艺技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Poly(lactic acid)/ basalt fiber (PLA/BF) composites were prepared by melt blending with a cross-linking agent, triallyl isocyanurate (TAIC). The thermal and mechanical properties of the composites were investigated through gel fraction, heat defection temperature (HDT), tensile tests and scanning electron microscopy (SEM). Under certain conditions, the HDT of composites was dramatically increased to 140篊 after irradiation. Tensile properties were enhanced as well. Both these improvements were consistent with changes of the fracture morphology. Compatibilization and concomitant enhancement of the interfacial adhesive between the polymer matrix and the inorganic fiber were achieved as seen from SEM photos, as a result of the formation of co-crosslinking and grafting structures at the interface according to the determination of gelation extraction.
分类: 物理学 >> 核物理学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: In order to study the effect of tensor force, we plan to perform a (p,d) reaction with a 4001600 MeV proton beam on the RIBLL2 at Lanzhou. Based on the experimental conditions of RIBLL2, a Monte Carlo method is used to simulate (p,d) reaction process. The distributions of primary beam and scattered deuterons are given on the target and at the F1, F2, F3, and F4 positions. Considering the yield of the deuteron, to separate the produced deuteron from the background particles, the target thickness is optimized. To obtain a clear particle identification spectrum by time of flight (TOF) and energy loss (E), the distance between the two detectors, as well as the energy and timing resolution of detectors are simulated. As a result, the distance between F2 and F4 is fit for that of TOF. After taking into account the particle distribution at F4, both sizes of Multi-Wire Drift Chamber, namely MWDC2 and MWDC3, are selected to be 50 mm50 mm.
分类: 物理学 >> 核物理学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: The experimental data of 100A MeV 12C + 12C elastic scattering are checked by using two-body kinematic calculation and 12C+p elastic scattering. It is shown that the measured data are true and reliable. In the paper, the transformation between the excited energy spectra of the 12C+12C system and the ground state energy spectra of the 12C+p system is introduced. The method of subtraction of the hydrogen background in the natural carbon target used in the experiment is elaborately described and the results are discussed. It is indicated that this method of subtraction of hydrogen background is reasonable and can be used in the data analysis. Based on the elastic scattering cross section of the previous experiment of 12C+p at 95.3A MeV, the hydrogen content entered into the reaction is analyzed. The final hydrogen content in the natural carbon target is (2.73 0.12)%.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: The luminescent properties of two Eu3+ compounds based on quinoline-2-carboxylic acid (Hqc), [Na2Eu2(qc)6(CH3COO)2(H2O)4].2DMF (1) and [Eu2(qc)6(H2O)6].3H2O (2), as well as their syntheses and structures are reported. Both compounds are formed by slow evaporation at room temperature and exhibit zero dimensional dinuclear structures. It is worth mentioning that a 4.5-fold enhancement in luminescent quantum yield is achieved by reducing the nonradiative deactivation, through which the quantum yield increases remarkably to 67.62% for 1 compared with 12.18% for 2.
分类: 核科学技术 >> 核材料与工艺技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: To study cytotoxic effect of heavy ion irradiation in the plateau region, and investigate whether autophagy induced by heavy ion irradiation is cytoprotective, HeLa cells were irradiated with 350 MeV/u carbon ions beams, and the clonogenic survival was analyzed. The results showed that cell survival decreased with increasing doses. It was also found that G2/M-phase cells increased, and the autophagy-related activity was significantly higher than the control. When autophagy was blocked by 3-methyladenine in carbon-ion irradiated cells, G2/M phase arrest and the percentage of apoptosis cells were further elevated, and cell survival decreased significantly, indicating the induction of cytoprotective autophagy by carbon-ion irradiation. Our results demonstrated that autophagy induced by carbon ion irradiation provided a self-protective mechanism in HeLa cells, short-time inhibition of autophagy before carbon-ion irradiation could enhance radiation cytotoxicity in HeLa cells.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2023-12-22
摘要: The infrared microspectroscopy beamline (BL06B) is a phase II beamline project at the Shanghai Synchrotron Radiation Facility (SSRF). The construction and optical alignment of BL06B were completed by the end of 2020. By 2021, it became accessible to users. The synchrotron radiation infrared (SRIR) source included edge radiation (ER) and bending-magnet radiation (BMR). The extracted angles in the horizontal and vertical directions were 40 and 20 mrad, respectively. The photon flux, spectral resolution, and focused spot size were measured at the BL06B end station, and the experimental results were consistent with theoretical calculations. SRIR light has a small divergence angle, high brightness, and a wide wavelength range. As a source of IR microscopy, it can easily focus on a diffraction-limited spatial resolution with a high signal-to-noise ratio (SNR). The BL06B end station can be applied in a wide range of research fields, including materials, chemistry, biology, geophysics, and pharmacology.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Coherent fading has been regarded as a critical issue in phase-sensitive optical frequency domain reflectometry ({\phi}-OFDR) based distributed fiber-optic sensing. Here, we report on an approach for fading noise suppression in {\phi}-OFDR with multi-core fiber. By exploiting the independent nature of the randomness in the distribution of reflective index in each of the cores, the drastic phase fluctuations due to the fading phenomina can be effectively alleviated by applying weighted vectorial averaging for the Rayleigh backscattering traces from each of the cores with distinct fading distributions. With the consistent linear response with respect to external excitation of interest for each of the cores, demonstration for the propsoed {\phi}-OFDR with a commercial seven-core fiber has achieved highly sensitive quantitative distributed vibration sensing with about 2.2 nm length precision and 2 cm sensing resolution along the 500 m fiber, corresponding to a range resolution factor as high as about about 4E-5. Featuring long distance, high sensitivity, high resolution, and fading robustness, this approach has shown promising potentials in various sensing techniques for a wide range of practical scenarios.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: Two coordination polymers (CPs), {[Ag(ADA)0.5(DPE)]·H2O}n (1) and {[Ag(ADA)0.5(Bipy)0.5]·H2O}n (2), (H2ADA = 3,3-azodibenzoic acid, DPE = 1,2-di(4-pyridyl)- ethylene, Bipy = 4,4΄-bipyridine), have been synthesized via solvothermal reactions of Ag+ with ADA2- and/or DPE, Bipy. CPs 1 and 2 were characterized by elemental analyses, IR spectra, thermal behaviors, and X-ray single-crystal diffraction. CPs 1 and 2 feature “Ag···Ag” subunits. CP 1 shows a 3D construction, in which the “Ag···Ag” subunits extend through ADA2- and DPE ligands using μ6-kO,O;kO;kO;kO,O;kO;kO and μ2-kO;kO coordination modes, respectively. It crystallizes in triclinic system, space group P, with a = 0.3808(18), b = 1.2476(6), c = 1.309(6) nm, α = 76.757(5), β = 84.649(5), γ = 86.809(5)º, V = 0.6024(5) nm3, Z = 2, Mr = 351.11, C13H11AgN2O3, Dc = 1.936 g/cm3, F(000) = 348, S = 1.064, R = 0.0323 and wR = 0.0689. CP 2 exhibits a 3D supramolecular structure, in which the “Ag···Ag” subunits are connected by ADA2- and DPE ligands with μ6-kO;kO;kO,O;kO;kO and μ2-kO;kO coordination modes, respectively. Ultimately, through hydrogen bond and π···π interaction, the “Ag···Ag” subunits stabilize the 3D supramolecular structure of 2. It crystallizes in monoclinic, space group C2/c, with a = 25.301(15), b = 13.197(8), c = 6.970(4) nm, β = 102.597(7)º, V = 2.271(2) nm3, Z = 8, C12H10AgN2O2.50, Mr = 330.09, Dc = 1.931 g/cm3, F(000) = 1304, S = 1.082, R = 0.1107 and wR = 0.2984. The fluorescence properties of CPs 1 and 2 have been also investigated.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: One new coordination polymer (CP) [Cd(bct)(bib)]·2(H2O) (1), based on 3,5-bis(4΄-carboxy- phenyl)-1,2,4-triazole (H2bct) and 1,4-bis(imidazol-1-ylmethyl)benzene(bib), has been synthesized by hydrothermal method, and its structure was determined and characterized by single-crystal X-ray diffraction analysis, elemental analysis, IR spectroscopy, and thermogravimetric analysis. The crystal structure of CP 1 is a three-dimensional framework with (3,5)-connected topology, where the bct ligands adopt a µ3-kO,kO,kO coordination mode connecting with three Cd centers and the bib ligands adopt a µ2-kN,kN coordination mode bridging two Cd ions. It crystallizes in monoclinic system, space group C2/c, with a = 2.6838(4), b = 1.24221(17), c = 1.8011(2) nm, β = 102.939(2)º, V = 5.8522(13) nm3, Z = 8, C30H27CdN7O6, Mr = 694.00, Dc = 1.566 g/cm3, F(000) = 2784, S = 1.055, R = 0.0294 and wR = 0.0731. Furthermore, solid-state photoluminescence measurements show that CP 1 produces strong emissions at room temperature.
分类: 核科学技术 >> 裂变堆工程技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: After the Fukushima nuclear accident in 2011, improvement actions of the environmental radiation surveillance were carried out by Chinese government to deal with the possible nuclear accident in response to the rapid development of nuclear power in China. The local government radiation surveillance system, including the on-line radiation monitoring network and automatic sampling system, the off-site monitoring center laboratory, the radioactive effluent on-line monitoring system and the sampling inspection laboratory were regulated to establish for all operation and constructing nuclear power plant. This paper describes the general design of the system by taking Ningde nuclear power plant (NPP) for example. The main designs, including radiation monitoring and sampling equipment, data collection and the communication technology, and the surveillance management, are generally based on the experiences or lessons from Fukushima accident. The system is expected to act as a pivotal role to evaluate the environmental radioactivity from the operation of NPP, and to provide effective decision support in the event of possible nuclear accident.
分类: 物理学 >> 核物理学 提交时间: 2023-11-22
摘要: BL10U2 is an undulator-based macromolecular crystallography (MX) beamline located at the 3.5-GeV Shanghai Synchrotron Radiation Facility. BL10U2 is specifically designed for conducting routine and bio safety level-2 (BSL-2) MX experiments utilizing high-flux tunable X-rays with energies from 7 to 18 keV, providing a beam spot size of 20 m (horizontal) 10 m (vertical) at the sample point. Certification by the Shanghai Pudong Municipal Health Commission confirmed the capability to perform BSL-2 MX experiments. The beamline is currently equipped with an Eiger X 16M detector and two newly developed in-house high-precision diffractometers that can be switched to perform conventional or in situ crystal diffraction experiments. An automatic sample changer developed in-house allows fast sample exchange in less than 30s, supporting high-throughput MX experimentation and rapid crystal screening. Data collection from both the diffractometer and detector was controlled by an in-house developed data collection software (Finback) with a user-friendly interface for convenient operation. This study presents a comprehensive overview of the facilities, experimental methods, and performance characteristics of the BL10U2 beamline.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The physics potential of detecting $^8$B solar neutrinos is exploited at the Jiangmen Underground Neutrino Observatory (JUNO), in a model independent manner by using three distinct channels of the charged-current (CC), neutral-current (NC) and elastic scattering (ES) interactions. Due to the largest-ever mass of $^{13}$C nuclei in the liquid-scintillator detectors and the potential low background level, $^8$B solar neutrinos would be observable in the CC and NC interactions on $^{13}$C for the first time. By virtue of optimized event selections and muon veto strategies, backgrounds from the accidental coincidence, muon-induced isotopes, and external backgrounds can be greatly suppressed. Excellent signal-to-background ratios can be achieved in the CC, NC and ES channels to guarantee the $^8$B solar neutrino observation. From the sensitivity studies performed in this work, we show that one can reach the precision levels of 5%, 8% and 20% for the $^8$B neutrino flux, $\sin^2\theta_{12}$, and $\Delta m^2_{21}$, respectively, using ten years of JUNO data. It would be unique and helpful to probe the details of both solar physics and neutrino physics. In addition, when combined with SNO, the world-best precision of 3% is expected for the $^8$B neutrino flux measurement.