分类: 物理学 >> 核物理学 提交时间: 2023-11-29
摘要: The phenomenology involved in severe accidents (SA) in nuclear reactors is highly complex. Currently, integrated analysis programs used for severe accident analysis heavily rely on custom empirical parameters, which introduce considerable uncertainty. Therefore, in recent years, the field of severe accidents has shifted its focus toward applying uncertainty analysis methods to quantify uncertainty in safety assessment programs, known as best estimate plus uncertainty (BEPU). This approach aids in enhancing our comprehension of these programs and their further development and improvement. This study concentrates on a third-generation pressurized water reactor (Gen-III PWR) equipped with advanced active and passive mitigation strategies. Through an Integrated Severe Accident Analysis Program (ISAA), numerical modeling and uncertainty analysis were conducted on severe accidents resulting from large break loss of coolant accidents (LBLOCA). Seventeen uncertainty parameters of the ISAA program were meticulously screened. Using Wilks' formula, the developed uncertainty program code, SAUP, was employed to carry out Latin hypercube sampling (LHS), while ISAA was employed to execute batch calculations. Statistical analysis was then conducted on two figures of merit (FOMs), namely, hydrogen generation and the release of fission products (FP) within the pressure vessel. Uncertainty calculations revealed that hydrogen production and the fraction of fission product released exhibited a normal distribution, ranging from 182.784 kg to 329.581 kg and from 15.6% to 84.3%, respectively. The ratio of hydrogen production to reactor thermal power fell within the range of 0.0578 to 0.104. A sensitivity analysis was performed for uncertain input parameters, revealing significant correlations between the failure temperature of the cladding oxide layer, maximum melt flow rate, size of the particulate debris, and porosity of the debris with both hydrogen generation and the release of fission products.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We use a cosmology-independent method to calibrate gamma-ray burst (GRB) from
the observational Hubble data (OHD) which obtained with the cosmic chronometers
method. By using Gaussian Process to reconstruct OHD, we calibrate the Amati
relation ($E_{\rm p}$--$E_{\rm iso}$) to construct a GRB Hubble diagram with
the A118 data set, and constrain Dark Energy models in a flat space with the
Markov Chain Monte Carlo numerical method. With the cosmology-independent GRBs
at $1.4
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We developed a GPU based single-pulse search pipeline (GSP) with candidate-archiving database. Largely based upon the infrastructure of Open source pulsar search and analysis toolkit (PRESTO), GSP implements GPU acceleration of the de-dispersion and integrates a candidate-archiving database. We applied GSP to the data streams from the commensal radio astronomy FAST survey (CRAFTS), which resulted in a quasi-real-time processing. The integrated candidate database facilitates synergistic usage of multiple machine-learning tools and thus improves efficient identification of radio pulsars such as rotating radio transients (RRATs) and Fast Radio Bursts (FRBs). We first tested GSP on pilot CRAFTS observations with the FAST Ultra-Wide Band (UWB) receiver. GSP detected all pulsars known from the the Parkes multibeam pulsar survey in the respective sky area covered by the FAST-UWB. GSP also discovered 13 new pulsars. We measured the computational efficiency of GSP to be ~120 times faster than the original PRESTO and ~60 times faster than a MPI-parallelized version of PRESTO.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We use a cosmology-independent method to calibrate gamma-ray burst (GRB) from
the observational Hubble data (OHD) which obtained with the cosmic chronometers
method. By using Gaussian Process to reconstruct OHD, we calibrate the Amati
relation ($E_{\rm p}$--$E_{\rm iso}$) to construct a GRB Hubble diagram with
the A118 data set, and constrain Dark Energy models in a flat space with the
Markov Chain Monte Carlo numerical method. With the cosmology-independent GRBs
at $1.4
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.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: In this Letter, a ring-core erbium-doped fiber (RC-EDF), with two-layer erbium-doped structure, supporting up to the fourth-order orbital angular momentum (OAM) mode is designed and fabricated for OAM mode multiplexed amplification. Using the RC-EDF, the third- and fourth-order OAM modes amplification with ultra-low differential mode gain (DMG) is demonstrated by observing both the modal intensity and phase distribution and measuring the modal gain under the fundamental mode core-pumping. The measured average gain of four modes (l=+3, -3, +4, -4) multiplexed amplification is higher than 19dB cover the C-band and the DMG is less than 1dB. Additionally, the gain of two conjugate OAM modes are almost the same under different pump power no matter they are amplified simultaneously or separately.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Chalcogenide glass (ChG) is an attractive material for integrated nonlinear photonics due to its wide transparency and high nonlinearity, and its capability of being directly deposited and patterned on Silicon wafer substrates. It has a singular Raman effect among amorphous materials. Yet, the Raman lasing performance in high quality and chip integrated ChG microresonators remains unexplored. Here, we demonstrate an engineered Raman lasing dynamic based on home developed photonic integrated high-Q ChG microresonators. With a quality factor above 10^6, we achieve the record-low lasing threshold 3.25 mW among integrated planar photonic platforms. Both the single-mode Raman lasers and a broadband Raman-Kerr comb are observed and characterized, which is dependent on the dispersion of our flexible photonic platform and engineered via tuning the waveguide geometric size. The tunability of such a chipscale Raman laser is also demonstrated through tuning the pump wavelength and tuning the operating temperature on the chip. This allows for the access of single-mode lasing at arbitrary wavelengths in the range 1615-1755 nm. Our results may contribute to the understanding of rich Raman and Kerr nonlinear interactions in dissipative and nonlinear microresonators, and on application aspect, may pave a way to chip-scale efficient Raman lasers that is highly desired in spectroscopic applications in the infrared.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Broadband Kerr combs with a flat comb spectral profile are expected in a number of applications, such as high-capacity optical communication. Here, we propose novel concentric dual-ring microresonators (DRMs) for advanced dispersion engineering to tailor the comb spectral profile. The dispersion can be flexibly engineered not only by the cross-section of the DRMs, but also by the gap between concentric dual-ring microresonators, which provides a new path to geometrically control the spectral profile of the soliton Kerr combs. An octave-spanning dissipative Kerr soliton comb with superior spectral flatness has been achieved numerically, covering from the telecommunication band to the mid-infrared (MIR) band region with a -40 dB bandwidth of 1265 nm (99.82 THz). Our results are promising to fully understand the nonlinear dynamics in hybrid modes in DRMs, which helps control broadband comb formation.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Optical tweezers can manipulate tiny particles. However, the distortion caused by the scattering medium restricts the applications of optical tweezers. Wavefront shaping techniques including the transmission matrix (TM) method are powerful tools to achieve light focusing behind the scattering medium. In this paper, we propose a new kind of TM, named intensity transmission matrix (ITM). Only relying on the intensity distribution, we can calculate the ITM with only about 1/4 measurement time of the widely used four-phase method. Meanwhile, ITM method can avoid the energy loss in diffraction introduced by holographic modulation. Based on the ITM, we have implemented particle manipulation with a high degree of freedom on single and multiple particles. In addition, the manipulation range is enlarged over twenty times (compared with the memory effect) to 200 {\mu}m.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Photonic integrated microcombs have enabled advanced applications in optical communication, microwave synthesis, and optical metrology, which in nature unveil an optical dissipative soliton pattern under cavity-enhanced nonlinear processes. The most decisive factor of microcombs lies in the photonic material platforms, where materials with high nonlinearity and in capacity of high-quality chip integration are highly demanded. In this work, we present a home-developed chalcogenide glasses-Ge25Sb10S65 (GeSbS) for the nonlinear photonic integration and for the dissipative soliton microcomb generation. Compared with the current integrated nonlinear platforms, the GeSbS features wider transparency from the visible to 11 um region, stronger nonlinearity, and lower thermo-refractive coefficient, and is CMOS compatible in fabrication. In this platform, we achieve chip-integrated optical microresonators with a quality (Q) factor above 2 x 10^6, and carry out lithographically controlled dispersion engineering. In particular, we demonstrate that both a bright soliton-based microcomb and a dark-pulsed comb are generated in a single microresonator, in its separated fundamental polarized mode families under different dispersion regimes. The overall pumping power is on the ten-milliwatt level, determined by both the high Q-factor and the high material nonlinearity of the microresonator. Our results may contribute to the field of nonlinear photonics with an alternative material platform for highly compact and high-intensity nonlinear interactions, while on the application aspect, contribute to the development of soliton microcombs at low operation power, which is potentially required for monolithically integrated optical frequency combs.