Neutron-proton scattering at next-to-next-to-leading order in Nuclear Lattice Effective Field Theory

We present a systematic study of neutron-proton scattering in Nuclear Lattice Effective Field Theory (NLEFT), in terms of the computationally efficient radial Hamiltonian method. Our leading-order (LO) interaction consists of smeared, local contact terms and static one-pion exchange. We show results for a fully non-perturbative analysis up to next-to-next-to-leading order (NNLO), followed by a perturbative treatment of contributions beyond LO. The latter analysis anticipates practical Monte Carlo simulations of heavier nuclei. We explore how our results depend on the lattice spacing a, and estimate sources of uncertainty in the determination of the low-energy constants of the next-to-leading-order (NLO) two-nucleon force. We give results for lattice spacings ranging from a = 1.97 fm down to a = 0.98 fm, and discuss the effects of lattice artifacts on the scattering observables. At a = 0.98 fm, lattice artifacts appear small, and our NNLO results agree well with the Nijmegen partial-wave analysis for S-wave and P-wave channels. We expect the peripheral partial waves to be equally well described once the lattice momenta in the pion-nucleon coupling are taken to coincide with the continuum dispersion relation, and higher-order (N3LO) contributions are included. We stress that for center-of-mass momenta below 100 MeV, the physics of the two-nucleon system is independent of the lattice spacing.Comment: 22 pages, 8 figure

Nuclear binding near a quantum phase transition

How do protons and neutrons bind to form nuclei? This is the central question of ab initio nuclear structure theory. While the answer may seem as simple as the fact that nuclear forces are attractive, the full story is more complex and interesting. In this work we present numerical evidence from ab initio lattice simulations showing that nature is near a quantum phase transition, a zero-temperature transition driven by quantum fluctuations. Using lattice effective field theory, we perform Monte Carlo simulations for systems with up to twenty nucleons. For even and equal numbers of protons and neutrons, we discover a first-order transition at zero temperature from a Bose-condensed gas of alpha particles (4He nuclei) to a nuclear liquid. Whether one has an alpha-particle gas or nuclear liquid is determined by the strength of the alpha-alpha interactions, and we show that the alpha-alpha interactions depend on the strength and locality of the nucleon-nucleon interactions. This insight should be useful in improving calculations of nuclear structure and important astrophysical reactions involving alpha capture on nuclei. Our findings also provide a tool to probe the structure of alpha cluster states such as the Hoyle state responsible for the production of carbon in red giant stars and point to a connection between nuclear states and the universal physics of bosons at large scattering length.Comment: Published version to appear in Physical Review Letters. Main: 5 pages, 3 figures. Supplemental material: 13 pages, 6 figure

Numerical Simulation of Aerodynamic Heating and Its Ground Test Simulation Technology

Numerical simulation and related experimental research on supersonic aerodynamic heating are important contents in the development of hypersonic vehicles. The boundary layer flow and heat transfer process in the supersonic aerodynamic heating phenomenon are analyzed, and the effects of the engineering model, gas model, turbulence model, grid scale, calculation scheme, and boundary conditions in aerodynamic heating simulation on the numerical simulation are discussed from the physical point of view. This paper introduces the test equipments commonly used in the research of aerodynamic heating, such as oxygebacetylene flame ablation, radiation heater and high enthalpy wind tunnel, and their advantages and disadvantages, also discusses the similar parameters in the ground simulation test, and points out the reasons for the over high heat flow of the cold wall

Waste sorting and its effects on carbon emission reduction: Evidence from China

Considering the importance of waste sorting and treatment in the development of an ecological civilization, empirically evaluating the environmental impact of such programs is particularly important. This study uses Xiao'er Township in Gong County, Sichuan Province, China as a case study to analyze and estimate the carbon emission reduction effects of the township's pilot waste sorting program. Using the five-point sampling method, samples of waste are collected, reviewed, and measured for their major components and other key indicators. Additionally, questionnaire surveys and interviews are conducted in the township, along with investigations into existing records and other relevant information. The study adopts the solid waste management-greenhouse gas (SWM-GHG) calculator to study the township data. The case study results imply that proper waste sorting and treatment methods in villages and townships could play a major role in the reduction of carbon emission. Specifically, after implementing waste sorting in Xiao'er, annual carbon emissions were reduced by 2081 tons—equivalent to the electricity consumption of a family of three people for 1718 years, or the amount of CO2 emitted by 264 1.6L vehicles driving once around the Earth. In the optimal scenario simulation, increasing the recycling of wet waste and recyclable waste further, the level of carbon emission reduction in Xiao'er could reach up to 4482 tons per year. According to the international general carbon trade price, this is equivalent to adding 44,820 US dollars to the GDP, or to an annual saving of 5.71 million kWh. If these waste management methods are expanded to villages and townships across China, then the carbon emissions reduced in a year would be equal to the CO2 emitted from electricity generation in Beijing for over a year. Based on these findings, this paper provides three policy recommendations for effective carbon emission reduction: increasing residents' environmental protection awareness over the long term, boosting funding support and enhancing the construction of supporting facilities, and strengthening governance and institutional capacity for waste sorting and treatment

Simultaneous radical cystectomy and colorectal cancer resection for synchronous muscle invasive bladder cancer and cT3 colorectal cancer: Our initial experience in five patients

To review cases of simultaneous radical cystectomy and colorectal cancer (CRC) resection for synchronous carcinoma of bladder and colorectum. Between May 1997 and September 2010, five patients were diagnosed with synchronous bladder cancer and CRCs. The primary colorectal tumors included three sigmoid cancers, one ascending colon cancer and one rectal cancer. All patients underwent simultaneous radical cystectomy and CRC resection. Pathologic types were confirmed by the biopsies of cystoscopy and colonoscopy. All patients were performed synchronous radical cystectomy and CRC resection. Four of them received adjuvant chemotherapies for CRC. Two of them died of liver metastasis 32.8 months and 13 months after surgery. Although patients with synchronous carcinoma of bladder and colorectum are rare, the Urologist should be alerted to this possibility when evaluating patients for the initially presenting symptoms and/or detected tumors. The simultaneous surgery is technically feasible for the selected patients

Multi-Antenna Jammer-Assisted Secure Short Packet Communications in IoT Networks

In this work, we exploit a multi-antenna cooperative jammer to enable secure short packet communications in Internet of Things (IoT) networks. Specifically, we propose three jamming schemes to combat eavesdropping, i.e., the zero forcing beamforming (ZFB) scheme, null-space artificial noise (NAN) scheme, and transmit antenna selection (TAS) scheme. Assuming Rayleigh fading, we derive new closed-form approximations for the secrecy throughput with finite blocklength coding. To gain further insights, we also analyze the asymptotic performance of the secrecy throughput in the case of infinite blocklength. Furthermore, we investigate the optimization problem in terms of maximizing the secrecy throughput with the latency and reliability constraints to determine the optimal blocklength. Simulation results validate the accuracy of the approximations and evaluate the impact of key parameters such as the jamming power and the number of antennas at the jammer on the secrecy throughput

Quantum Cutting in KGd(CO₃)₂:Tb³⁺ Green Phosphor

Phosphors with a longer excitation wavelength exhibit higher energy conversion efficiency. Herein, quantum cutting KGd(CO3)2:Tb3+ phosphors excited by middle-wave ultraviolet were synthesized via a hydrothermal method. All the KGd(CO3)2:xTb3+ phosphors remain in monoclinic structures in a large Tb3+ doping range. In the KGd(CO3)2 host, 6D3/2 and 6I17/2 of Gd3+ were employed for quantum cutting in sensitizing levels. The excited state electrons could easily transfer from Gd3+ to Tb3+ with high efficiency. There are three efficient excited bands for quantum cutting. The excited wavelengths of 244, 273, and 283 nm correspond to the transition processes of 8S7/2→6D3/2 (Gd3+), 8S7/2→6I17/2 (Gd3+), and 7F6→5F4 (Tb3+), and the maximum quantum yields of KGd(CO3)2:Tb3+ can reach 163.5, 119, and 143%, respectively. The continuous and efficient excitation band of 273–283 nm can well match the commercial 275 nm LED chip to expand the usage of solid-state light sources. Meanwhile, the phosphor also shows good excitation efficiency at 365 nm in a high Tb3+ doping concentration. Therefore, KGd(CO3)2:Tb3+ is an efficient green-emitting phosphor for ultraviolet-excited solid-state light sources

Optimal Channel Training Design for Secure Short-Packet Communications

Physical layer security is a promising technique to ensure the confidentiality of short-packet communications, since no additional channel uses are needed. Motivated by the fact of finite coding blocklength in short-packet communications, we attempt to investigate the problem of how many the channel uses utilized for channel training should be allocated to perform secure communications. Based on the finite blocklength information theory, we derive a closed-form expression to approximate the average achievable secrecy throughput. To gain more insights, we also present the asymptotic average secrecy throughput under two special cases, i.e., high signal-to-noise ratio (SNR) and infinite blocklength. Moreover, we determine the optimal channel training length to maximize the average secrecy throughput under the reliability constraint and given blocklength. Numerical results are provided to validate the analysis and demonstrate that the performance gain achieved by the optimal channel training length is remarkable, relative to other benchmark schemes