A quality control framework for digital fabrication with concrete

The quality control of digital fabrication with concrete has more stringent requirements than traditional casting. Firstly, since formwork is typically absent, or removed at an early stage in production, the material is exposed to external influences that can result in deformations, collapse, or deterioration. Therefore, the evolution of properties during the process has to be controlled. Secondly, the fabrication systems are typically more sensitive to dosing fluctuations, and the produced, optimized objects are more sensitive to defects, which requires the process variations to be controlled at a higher resolution. A framework is presented that categorizes quality control experiments into destructive and non-destructive, according to their systematic error, and according to the location of testing with respect to the process. This framework is applied to the fresh state mechanical performance of concrete and quality control strategies are derived from it. Lastly, research gaps are identified that are critical for the further development and adoption of these quality control strategies in digitally fabricated concrete

A quality control framework for digital fabrication with concrete

The quality control of digital fabrication with concrete has more stringent requirements than traditional casting. Firstly, since formwork is typically absent, or removed at an early stage in production, the material is exposed to external influences that can result in deformations, collapse, or deterioration. Therefore, the evolution of properties during the process has to be controlled. Secondly, the fabrication systems are typically more sensitive to dosing fluctuations, and the produced, optimized objects are more sensitive to defects, which requires the process variations to be controlled at a higher resolution. A framework is presented that categorizes quality control experiments into destructive and non-destructive, according to their systematic error, and according to the location of testing with respect to the process. This framework is applied to the fresh state mechanical performance of concrete and quality control strategies are derived from it. Lastly, research gaps are identified that are critical for the further development and adoption of these quality control strategies in digitally fabricated concrete

High energy solar neutrinos and p-wave contributions to ^3He(p,\nue^+)^4He

High energy solar neutrinos can come from the hep reaction ^3He(p,\nue^+)^4He with a large end point energy of 18.8 MeV. Understanding the hep reaction may be important for interpreting solar neutrino spectra. We calculate the contribution of the axial charge transition $^3P_0\to ^1S_0$ to the hep thermonuclear S factor using a one-body reaction model involving a nucleon moving in optical potentials. Our result is comparable to or larger than previous calculations of the s-wave Gamow Teller contribution. This indicates that the hep reaction may have p-wave strength leading to an enhancement of the S factor.Comment: 4 pages, 1 ps figure, very minor changes, Phys. Rev. C in pres

Incidence of glaucomatous visual field loss after two decades of follow-up: the Rotterdam Study

To determine the incidence of glaucomatous visual field loss (GVFL) two decades after the start of the Rotterdam Study, and to compare known risk factors for open-angle glaucoma (OAG) between different clinical manifestations of OAG. Of 6806 participants aged 55 years and older from the population-based Rotterdam Study, 3939 underwent visual field testing at baseline and at least one follow-up round. The ophthalmic examinations included optic disc assessment and measurements of intraocular pressure (IOP), refractive error, diastolic blood pressure (DBP), and height and weight. The incidence rate of GVFL was calculated. Associations with the risk factors age, gender, baseline IOP, family history, myopia, DBP, and body-mass index [BMI] were assessed using Cox regression, with different clinical manifestations of OAG as outcome measure (glaucomatous optic neuropathy (GON), GVFL, GVFL and GON, GVFL without GON, and GON without GVFL). Median follow-up was 11.1 (IQR 6.8–17.2; range 5.0–20.3) years. The incidence rate of GVFL was 2.9 (95% confidence interval 2.4–3.4) per 1000 person years (140 cas

Inverting Time-Dependent Harmonic Oscillator Potential by a Unitary Transformation and a New Class of Exactly Solvable Oscillators

A time-dependent unitary (canonical) transformation is found which maps the Hamiltonian for a harmonic oscillator with time-dependent real mass and real frequency to that of a generalized harmonic oscillator with time-dependent real mass and imaginary frequency. The latter may be reduced to an ordinary harmonic oscillator by means of another unitary (canonical) transformation. A simple analysis of the resulting system leads to the identification of a previously unknown class of exactly solvable time-dependent oscillators. Furthermore, it is shown how one can apply these results to establish a canonical equivalence between some real and imaginary frequency oscillators. In particular it is shown that a harmonic oscillator whose frequency is constant and whose mass grows linearly in time is canonically equivalent with an oscillator whose frequency changes from being real to imaginary and vice versa repeatedly.Comment: 7 pages, 1 figure include