581 research outputs found
Global reaction mechanisms for MILD oxy-combustion of methane
No full textAbstract not availableFan Hu, Pengfei Li, Junjun Guo, Zhaohui Liu, Lin Wang, Jianchun Mi, Bassam Dally, Chuguang Zhen
Fig. 3 in Structurally diverse and bioactive alkaloids from an insect-derived fungus Neosartorya fischeri
No full textFig. 3. Selected NOESY/ROESY correlations of compounds 1–4, 8, 12, and 16.Published as part of Lin, Shuang, He, Yan, Li, Fengli, Yang, Beiye, Liu, Mengting, Zhang, Sitian, Liu, Junjun, Li, Huaqiang, Qi, Changxing, Wang, Jianping, Hu, Zhengxi & Zhang, Yonghui, 2020, Structurally diverse and bioactive alkaloids from an insect-derived fungus Neosartorya fischeri, pp. 1-10 in Phytochemistry (112374) 175 on page 4, DOI: 10.1016/j.phytochem.2020.112374, http://zenodo.org/record/829536
In-line inspection of unpiggable buried live gas pipes using circumferential EMAT guided waves
No full textForecast Uncertainty Quantification using Monte Carlo, Polynomial Chaos Expansion and Unscented Transformation Methods
No full textIn the context of prediction science, the sources of uncertainty can be from the uncertainties of the experiments, modeling, model inputs, numerical analysis, etc. This study concentrates on quantifying the forecast uncertainty arising from the propagation of the uncertainties in the model inputs to the dynamical model. The uncertainties in the inputs include the randomness in (1) the initial conditions, (2) the forcing term (including both the external forcing and the boundary conditions), and (3) randomness in the parameters of the model. In order to quantify the uncertainties in the forecast, three uncertainty quantification (UQ) methods are studied, namely classical Monte Carlo (MC), polynomial chaos (PC) expansion and unscented transformation (UT). Using MC as the benchmark, two dynamical models are used in this study to examine the performance of PC expansion and UT. One is the low order (two components) spectral solution to the nonlinear advection equation, and the other one is the five-variable mixed-layer model which is used to describe the return flow event over the Gulf of Mexico during the cool season (between November and March) every year. The experimental results and the comparisons with MC have shown that both PC and UT can provide good estimates on the statistical information relating to the forecast, for example, the mean, variation (or standard deviation), covariance. The approach of UT utilizes a set of deterministically chosen sigma points to propagate the uncertainties contained in the inputs through the dynamical model. Only the first two moments of the forecast can be estimated by UT. Different from UT, the PC expansion represents the stochastic process in the form of a series expression (hence a surrogate approximation) in terms of the orthogonal polynomials whose type depends on the probability distribution of the random inputs. Ensemble forecast can be achieved by sampling the random variable used in the PC expansion. Furthermore, the histogram of the forecast can be constructed using the ensemble forecast, and then one can estimate the probability density function (PDF) of the forecast. What’s more, PC expansion can also give estimates on the statistics of higher order moments. The application of PC and UT in quantifying the forecast uncertainties in large scale system, the combination with data assimilation techniques and its real applications, and the ability to deal with nonGaussian distributions will be some of the topics for future study
A joint decision model of variant selection and inventory control based on demand forecasting
No full text
Titanium isotopes and rare earth patterns in CAIs: Evidence for thermal processing and gas-dust decoupling in the protoplanetary disk
No full textTitanium isotopic compositions (mass-dependent fractionation and isotopic anomalies) were measured in 46 calcium-, aluminum-rich inclusions (CAIs) from the Allende CV chondrite. After internal normalization to ^(49)Ti/^(47)Ti, we found that ε^(50)Ti values are somewhat variable among CAIs, and that ε^(46)Ti is highly correlated with ε^(50)Ti, with a best-fit slope of 0.162 ± 0.030 (95% confidence interval). The linear correlation between ε^(46)Ti and ε^(50)Ti extends the same correlation seen among bulk solar objects (slope 0.184 ± 0.007). This observation provides constraints on dynamic mixing of the solar disk and has implications for the nucleosynthetic origin of titanium isotopes, specifically on the possible contributions from various types of supernovae to the solar system. Titanium isotopic mass fractionation, expressed as δ′^(49)Ti, was measured by both sample-standard bracketing and double-spiking. Most CAIs are isotopically unfractionated, within a 95% confidence interval of normal, but a few are significantly fractionated and the range δ′^(49)Ti is from ∼−4 to ∼+4. Rare earth element patterns were measured in 37 of the CAIs. All CAIs with significant titanium mass fractionation effects have group II and related REE patterns, implying kinetically controlled volatility fractionation during the formation of these CAIs
The Simulation of Offshore Radioactive Substances Diffusion Based on MIKE21: A Case Study of Jiaozhou Bay
No full textNuclear accident-derived radionuclide dispersion poses critical challenges to marine ecological sustainability and human–ocean interdependence. While existing studies focus on hydrodynamic modeling of pollutant transport, the link between nuclear safety and sustainable ocean governance remains underexplored. This study investigates radionuclide diffusion patterns in semi-enclosed bays using a high-resolution coupled hydrodynamic particle-tracking model, explicitly addressing threats to marine ecosystem stability and coastal socioeconomic resilience. Simulations revealed that tidal oscillations and topographic constraints prolong pollutant retention by 40% compared to open seas, elevating local concentration peaks by 2–3× and intensifying bioaccumulation risks in benthic organisms. These findings directly inform sustainable marine resource management: the identified high-risk zones enable targeted monitoring of fishery resources, while diffusion pathways guide coastal zoning policies to decouple economic activities from contamination hotspots. Compared to Fukushima’s open-ocean dispersion models, our framework uniquely quantifies how semi-enclosed geomorphology exacerbates localized ecological degradation, providing actionable metrics for balancing nuclear energy development with UN Sustainable Development Goals (SDGs) 14 and 3. By integrating hydrodynamic specificity with ecosystem vulnerability thresholds, this work advances science-based protocols for sustainable nuclear facility siting and marine spatial planning
Building a Hospital Pharmacist Workforce by a Diversified and Position-Oriented Learning System
No full textWei He, Yangmin Hu, Difei Yao, Junjun Xu, Yunjian Dai, Haibin Dai Department of Pharmacy, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, People’s Republic of ChinaCorrespondence: Haibin Dai, Department of Pharmacy, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, People’s Republic of China, Email [email protected]: The role of hospital pharmacists has shifted from primarily ensuring drug supply to providing comprehensive pharmaceutical care. To accommodate this shift, new positions are needed. The traditional training model for hospital pharmacists is no longer sufficient for the evolving demands of pharmaceutical care and these new roles. This study aimed to describe the development of a position-oriented learning system explicitly tailored for hospital pharmacists and to assess its impact on workforce development and pharmacy service.Methods: The position-oriented learning system for hospital pharmacists, aimed at enhancing training and workforce development, was evaluated based on two critical criteria: the completion rate of learning modules and the subsequent improvement in pharmaceutical care at the hospital. The completion rate assessed the engagement and effectiveness of the training content. At the same time, the improvement in pharmaceutical care evaluated practical outcomes such as percentages of patients who received pharmaceutical care and percentages of inappropriate medication orders intercepted.Results: In 2021, 218 employees participated in the learning system. The pharmacy department has identified 22 pharmacists for various positions through this system. The quantity and quality of pharmaceutical care have improved significantly.Conclusion: The position-oriented diversified learning system achieves the perfect combination of department development direction and individual career planning of employees. The learning system can significantly improve the learning efficiency of pharmacists, enhance the quality of various pharmaceutical care, and promote the development of disciplines.Keywords: learning system, position-oriented, clinical pharmacist, informatics pharmacis
Thermodynamics and kinetics of large hydrocarbon reaction using ab initio calculations
No full textPh.D.It remains a long-standing challenge to predict accurate thermodynamics and kinetics of large hydrocarbons by first-principle calculations. This is mainly caused by the very high computational cost for high-accuracy electronic structure calculations and overwhelming complexity for anharmoncity treatment in large reaction systems. Developing or validating accurate and efficient quantum chemistry methods is the prerequisite to remove the hurdles towards large hydrocarbon reaction models.This thesis proposes several new methods to enable cost-effective and accurate calculations of the thermodynamics and kinetics of large hydrocarbons such as bond dissociation energies, enthalpies, entropies and rate constants. Firstly, a two-layer ONIOM-CCSD(T)/CBS method, which treats the high layer with CCSD(T) method and the low layer with DFT method, was developed to calculate the C−C bond dissociations energies of C₆-C₂₀ normal alkanes. Secondly, a novel cascaded group-additivity ONIOM method, namely CGA-ONIOM, was developed to approach the globally accurate electronic energies at the CCSD(T)/CBS theory level. A systematic validation against 79 C₄-C₈ hydrocarbons was implemented to justify the accuracy of CGA-ONIOM. Further application of CGA-ONIOM to 12 representative C₁₀, C₁₂ and C₁₆ aliphatic hydrocarbons was also conducted. Thirdly, the multi-structural 2-dimensional torsion method (MS-2DT) based on minimally coupled approximation was proposed to treat the low-frequency anharmonicity presented in large flexible hydrocarbons. This method has been used to calculate the standard entropies and heat capacities of 18 C₆−C₈ alkanes with 5-7 torsions.Finally, the CGA-ONIOM-DFT and ONIOM-DFT schemes were proposed to calculate the rate constants of medium-to-large hydrocarbon reaction systems. This scheme advocates to adopt CGA-ONIOM or ONIOM for barrier height benchmarks to further select the best-performance DFT method. The DFT method is then employed to study the reaction kinetics. The rate constants of medium-size reaction system, i.e., cyclopentane + OH reaction, were treated by the CGA-ONIOM-DFT scheme with the selected density functional M06-2X. The rate constant of cyclopentane with OH was calculated at 200-2000 K by multi-structural canonical variational transition state theory including small-curvature tunneling (MS-CVT/SCT) method. The predictions are in good agreement with the experimental data at combustion and atmospheric temperatures with a deviation of less than 30%. Moreover, the reaction of JP-10 with OH was selected as the prototypical large complex reaction system to demonstrate the feasibility of the ONIOM-DFT scheme. Site-specific rate constants of JP-10 + OH were predicted by MS-CVT/SCT theory. Our predictions agree well with the experimental measurements by a factor of ~1.5.These studies demonstrate the utility of ONIOM, CGA-ONIOM, MS-2DT and CGA-ONION-DFT and ONIOM-DFT methods to predict the thermodynamics and kinetics of large hydrocarbons. The ONIOM method enables a fast prediction of the BDEs of large hydrocarbons at the CCSD(T)/CBS theory level. The CGA-ONIOM method computes the globally accurate energies of large hydrocarbons. Remarkably, the CGA-ONIOM method improves the computational efficiency by up to four orders of magnitude compared with conventional CCSD(T) calculations and maintains the accuracy. The MS-2DT treats the multi-structural torsional anharmonicity at the reduced computational cost compared to the conventional MS-T method. The CGA-ONIOM-DFT and ONIOM-DFT methods provide an affordable solution to the direct dynamics of large reaction systems. By validating these theoretical methods against the experimental measurements, these methods open up new opportunities of studying the large hydrocarbon systems accurately and efficiently.從第一性原理出發，準確預測大型碳氫反應體系的熱力學、動力學參數面臨長期的挑戰。該挑戰主要在於高精度的電子結構計算耗時巨大，以及大分子反應體系的非諧效應的處理極其複雜。因此，開發準確高效的量子化學方法是發展大型碳氫反應模型的前提。本論文提出了若干新方法以實現碳氫大分子熱力學、動力學參數的高效計算。通過此類方法，諸多關鍵信息如斷鍵能、標準生產焓、標準熵以及速率常數均可得以預測。本論文提出了一種雙層的ONIOM-CCSD(T)/CSB方法，該方法對高層部分展開CCSD(T)計算，而對低層展開了DFT計算。該方法用於計算了正己烷至正廿烷的碳-碳斷鍵能。利用基團貢獻法（GA）和ONIOM方法，本文提出了CGA-ONIOM來獲得精度接近於CCSD(T)/CBS水平的精確的電子能量。該方法被用於計算七十九種丁烷至辛烷分子的電子能量以及標準生成焓，論證了該方法的可行性。隨後，CGA-ONIOM方法被進一步用於計算12種典型的碳氫體系的標準生成焓，包括碳十、碳十二以及碳十六分子。基於最小耦合近似，本文提出了多結構-二維扭轉方法用於處理碳氫柔性大分子的低頻非諧振效應。該方法用於計算己烷至辛烷等十八種碳氫分子的標準熵和比熱容，且所選定的碳氫分子具有五到七個扭轉模式。最後，本文提出了CGA-ONIOM-DFT與ONIOM-DFT計算框架用於獲取中大型碳氫反應體系的速率常數。該框架建議採用CGA-ONIOM或ONIOM方法獲取勢壘高度的基準值，並利用該基準值對一系列DFT方法進行篩選從而獲得性能最佳的DFT方法。該DFT方法隨後用於反應動力學計算。為展示該框架的有效性，選取了環戊烷與羥基這一中型反應進行研究。研究表明M06-2X密度泛函方法對於該反應體系的計算性能最佳。在此基礎上，本文利用多結構-變分過渡態理論以及多維小曲率隧穿方法（MS-CVT/SCT）對200-2000 K範圍內的速率常數進行了計算。本文的理論預測結果與寬溫度範圍內的實驗測量值吻合很好，二者偏差僅在30%以內。此外，本文進一步以JP-10與羥基反應體系這一典型的大型複雜碳氫體系為代表，論證了ONIOM-DFT框架的可行性。本文利用MS-CVT/SCT方法獲取了不同位點的反應速率常數。本文計算的反應速率常數與實驗數據吻合較好，二者進存在1.5倍的差距。上述研究展示ONIOM、CGA-ONIOM、MS-2DT以及CGA-ONIOM-DFT與ONIOM-DFT等方法在大型碳氫反應體系的熱力學、動力學參數計算方法的應用。ONIOM方法可在CCSD(T)/CBS 水平下實現對碳氫大分子斷鍵能的快速預測。CGA-ONIOM方法在保證計算精度的前提下可提高傳統的CCSD(T) 計算效率，最高幅度可達四個量級。與MS-T方法相比，MS-2DT方法以較小的計算量即可實現對多結構-扭轉非諧性的處理。CGA-ONIOM-DFT與ONIOM-DFT方法為大型反應體系的直接動力學模擬提供了可行方案，採用上述兩種框架獲得的速率常數均與實驗吻合良好。因此，以上諸方法使碳氫大分子體系的高效高精度研究成為可能。Wu, Junjun."November 2019."Thesis Ph.D. Chinese University of Hong Kong 2020.Includes bibliographical references (leaves 122-134).Abstracts also in Chinese.Title from PDF title page (viewed on 12, April 2021)
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