摘要 :
Sandia National Laboratories developed the DaMaGe Initiated Reaction (DMGIR) model to numerically predict weakly supported shock waves that generate an initiation at energy levels below the shock-to-detonation transition (SDT) of ...
展开
Sandia National Laboratories developed the DaMaGe Initiated Reaction (DMGIR) model to numerically predict weakly supported shock waves that generate an initiation at energy levels below the shock-to-detonation transition (SDT) of an explosive. The DMGIR model couples the strain energy fluence contribution from damage to the initiation process. It does not attempt to include all possible specific initiation mechanisms at the mesoscale, but instead looks at cumulative damage incurred in the explosive through experimental calibration of a small number of material constants. Both shock pressure (hydrostatic) and shear stress (deviatoric) are accounted for in the summation. The model was designed to be robust and relatively simple to calibrate. The DMGIR model is implemented into the Sandia National Laboratories' CTH shock wave and large deformation code. The model runs concurrently with the existing History Variable Reactive Burn (HVRB) model currently used for shock initiation.
收起
摘要 :
Sandia National Laboratories developed the DaMaGe Initiated Reaction (DMGIR) model to numerically predict weakly supported shock waves that generate an initiation at energy levels below the shock-to-detonation transition (SDT) of ...
展开
Sandia National Laboratories developed the DaMaGe Initiated Reaction (DMGIR) model to numerically predict weakly supported shock waves that generate an initiation at energy levels below the shock-to-detonation transition (SDT) of an explosive. The DMGIR model couples the strain energy fluence contribution from damage to the initiation process. It does not attempt to include all possible specific initiation mechanisms at the mesoscale, but instead looks at cumulative damage incurred in the explosive through experimental calibration of a small number of material constants. Both shock pressure (hydrostatic) and shear stress (deviatoric) are accounted for in the summation. The model was designed to be robust and relatively simple to calibrate. The DMGIR model is implemented into the Sandia National Laboratories’ CTH shock wave and large deformation code. The model runs concurrently with the existing History Variable Reactive Burn (HVRB) model currently used for shock initiation.
收起
摘要 :
This review highlights 20 years of research concerning the synthesis of block copolymer structures with dual and,more general,heterofunctional initiators,allowing the combination of mechanistically distinct polymerization reaction...
展开
This review highlights 20 years of research concerning the synthesis of block copolymer structures with dual and,more general,heterofunctional initiators,allowing the combination of mechanistically distinct polymerization reactions without the need for intermediate transformation and protection steps.This strategy,which has known an exponential growth since the year 2000,has offered new opportunities in the design and application of functional polymeric materials for a broad spectrum of emerging technologies.Block copolymer structures with both linear (AB,ABA,(AB)_n,multiblocks,etc) and branched macromolecular architectures (star block,graft,miktoarm star,dendrimer-like,...),obtained by the combination of uncontrolled and/or controlled polymerization reactions starting from a single molecule,are discussed.Not only small organic molecules but also polymers containing two initiation functions,further referred to as macro dual initiators,which can initiate different polymerizations independently and selectively,are described.
收起
摘要 :
The dependence of the initial electron-beam parameters on absorbed dose distributions have been investigated using a CyberKnife radiotherapy accelerator (Accuray, United States). To describe the initial electron-beam characteristi...
展开
The dependence of the initial electron-beam parameters on absorbed dose distributions have been investigated using a CyberKnife radiotherapy accelerator (Accuray, United States). To describe the initial electron-beam characteristics, simulations of the linear electron accelerator are performed and the electron distributions in the beam of a linac output are analyzed. The radial distributions of electrons are assumed exponential, whereas the energy electron distributions are approximated by monoenergetic and rectangular spectra. There is no significant dependence of depth-dose curves in a phantom on the shape of the electron beam. Importantly, a clear dependence of the radiation field profile on the size of the electron beam is observed not just in the penumbra region, but also in the open part.
收起
摘要 :
At very small strains the tensile stress-strain relationship of elastomers is often fairly linear and therefore might be used for obtaining initial tensile modulus E. In this work we analysed initial tensile data of unfilled and c...
展开
At very small strains the tensile stress-strain relationship of elastomers is often fairly linear and therefore might be used for obtaining initial tensile modulus E. In this work we analysed initial tensile data of unfilled and carbon black filled vulcanised SBR samples to test if this is feasible.
收起
摘要 :
Getting the right number of initials on the casing is critical in achieving the optimum yield, quality and ease of picking of mushroom crops. Ralph Noble and Andreja Dobrovin-Pennington of HRI have identified factors in the casing...
展开
Getting the right number of initials on the casing is critical in achieving the optimum yield, quality and ease of picking of mushroom crops. Ralph Noble and Andreja Dobrovin-Pennington of HRI have identified factors in the casing that could eventually be used to control the initiation of the crop. It is known that the number of developing initials can be manipulated by changes in the cropping environment and casing watering regime, but there is a tendency for the results to be variable even with apparently similar conditions. This can have a significant effect on the profitability of the crop. Producing too many initials will result in small, poor quality mushrooms that are difficult to pick, whereas producing too few initials will result in loweryields.
收起
摘要 :
This study examines the initiation of two intracloud (IC) and two cloud-to-ground (CG) lightning flashes using electric field change (FA) sensors and VHF (LogRF) sensors located at seven sites near Oxford, Mississippi, USA. For ea...
展开
This study examines the initiation of two intracloud (IC) and two cloud-to-ground (CG) lightning flashes using electric field change (FA) sensors and VHF (LogRF) sensors located at seven sites near Oxford, Mississippi, USA. For each flash the initiating event caused a pulse in the LogRF data and started an Initial E-Change (IEC) in the FA data. The initiating LogRF pulses had powers < 1 W and durations of similar to 1 mu s. Numerous LogRF pulses occurred during each IEC; these pulses had durations <= 3 mu s. Fewer FA pulses occurred during each IEC; these pulses had durations of <= 7 mu s. During each IEC, a few of the LogRF pulses were coincident with a FA pulse, and most such pairs of pulses enhanced the IEC; no IEC enhancing events occurred without such a coincident pair. Each flash had 1 or 2 IEC enhancing events soon after the initiating event and 1 or 2 enhancing events shortly before the first classic initial breakdown (IB) pulse occurred. The point dipole moments and durations of IECs of the two IC flashes were (-520C m, 620 mu s) and (-770C m, 1790 mu s) and for the two CG flashes were (9C m, 124 mu s) and (36C m, 130 mu s). We speculate that the LogRF events were positive corona streamers, that enhancing events occurred when a new streamer extended a previous streamer path, and that this process during the flash initiation developed a nascent channel needed for the negative breakdown of the IB pulses.
收起
摘要 :
The behavior of silver and lead azides (laminated and filiform crystals, pressed powders) with initiation of their explosive decomposition by a laser pulse is studied. The initiation energy thresholds are measured during irradiati...
展开
The behavior of silver and lead azides (laminated and filiform crystals, pressed powders) with initiation of their explosive decomposition by a laser pulse is studied. The initiation energy thresholds are measured during irradiation at wavelengths of 1064, 532, 354.7, and 266 nm corresponding to four harmonics of laser radiation. Irradiation is performed under conditions with the sample surface being open or covered with a transparent dielectric (quartz plate) with a pressing force up to 5 · 10~8 N/m~2. Surface covering does not exert any significant effect on the initiation energy threshold in the domain of transparency of the heavy metal azide matrix (first and second radiation harmonics). In the domain of bandgap absorption (fourth harmonic), the initiation threshold strongly depends on the surface conditions (open/covered). The results are discussed from the viewpoint of the influence of the transparent substrate on gas-dynamic unloading of the heat spot, which is formed in the domain of bandgap absorption owing to laser radiation absorption in a thin subsurface layer.
收起
摘要 :
In the data pipeline from the data collection process to the planned statistical analyses, initial data analysis (IDA) typically takes place between the end of the data collection and do not touch the research questions. A systema...
展开
In the data pipeline from the data collection process to the planned statistical analyses, initial data analysis (IDA) typically takes place between the end of the data collection and do not touch the research questions. A systematic process for IDA and clear reporting of the findings would help to understand the potential shortcomings of a dataset, such as missing values, or subgroups with small sample sizes, or shortcomings in the collection process, and to evaluate the impact of these shortcomings on the research results. A clear reporting of findings is also relevant when making datasets available to other researchers. Initial data analyses can provide valuable insights into the suitability of a data set for a future research study. Our aim was to describe the practice of reporting of initial data analyses in observational studies in five highly ranked medical journals with focus on data cleaning, screening, and reporting of findings which led to a potential change in the analysis plan. This review was carried out using systematic search strategies with eligibility criteria for articles to be reviewed. A total of 25 papers about observational studies were selected from five medical journals published in 2018. Each paper was reviewed by two reviewers and IDA statements were further discussed by all authors. The consensus was reported. IDA statements were reported in the methods, results, discussion, and supplement of papers. Ten out of 25 papers (40%) included a statement about data cleaning. Data screening statements were included in all articles, and 18 (72%) indicated the methods used to describe them. Item missingness was reported in 11 papers (44%), unit missingness in 15 papers (60%). Eleven papers (44%) mentioned some changes in the analysis plan. Reported changes referred to missing data treatment, unexpected values, population heterogeneity and aspects related to variable distributions or data properties. Reporting of initial data analyses were sparse, and statements on IDA were located throughout the research articles. There is a lack of systematic reporting of IDA. We conclude the article with recommendations on how to overcome shortcomings in the practice of IDA reporting in observational studies.
收起
原文获取