Full monitoring of ensemble trajectories with 10 dB-sub-Heisenberg imprecision

The change of a quantum state can generally only be fully monitored through simultaneous measurements of two non-commuting observables $$\hat{X}$$ X ̂ and $$\hat{Y}$$ Y ̂ spanning a phase space. A measurement device that is coupled to the thermal environment provides at a time a pair of values that have a minimal uncertainty product set by the Heisenberg uncertainty relation, which limits the precision of the monitoring. Here, we report on an optical ensemble measurement setup that is able to monitor the time-dependent change of the quantum state’s displacement in phase space ($$\langle \hat{X}(t)\rangle ;\langle \hat{Y}(t)\rangle$$ ⟨ X ̂ ( t ) ⟩ ; ⟨ Y ̂ ( t ) ⟩ ) with an imprecision 10 dB below the Heisenberg uncertainty limit. Our setup provides pairs of values (X(ti); Y(ti)) from simultaneous measurements at subsequent times ti. The measurement references are not coupled to the thermal environment but are established by an entangled quantum state. Our achievement of a tenfold reduced quantum imprecision in monitoring arbitrary time-dependent displacements supports the potential of the quantum technology required for entanglement-enhanced metrology and sensing as well as measurement-based quantum computing.

Effect of Silica Fume on Metakaolin Geopolymers’ Sulfuric Acid Resistance

To demonstrate the importance of the Si/Al ratio in terms of geopolymer mix designs for acid resistance, a metakaolin-based geopolymer was modified by replacing the aforementioned precursor with different percentages of silica fume. Durability tests were performed by exposing geopolymers with varying amounts of silica fume (up to 9%) to sulfuric acid solution (pH 1) over a period of 84 days. Geopolymer samples were analyzed by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) before and after 7, 14, 28, 56 and 84 days of exposure. To show the time-dependent change of the elemental composition in the corroded layer after sulfuric acid attack, SEM-EDX elemental mappings were conducted and divided into 100 µm segments to generate element-specific depth profiles. The results show that above a critical silica fume content, the erosion of the sample surface by complete dissolution can be prevented and higher amounts of silica fume lead to a significant densification of large (protective) areas of the corroded layer, which delays the progress of corrosion.

Strength of AAAS Composites with Ceramic Precursor over Time

The paper deals with the approximation of the time evolution of the strengths of selected alkali-activated aluminosilicate (AAAS) composites based on ceramic precursors. Composites made of brick dust as a precursor and an alkaline activator with a silicate modulus of Ms = 0.8, 1.0, 1.2, 1.4, and 1.6 were investigated. The filler consisted of standard quartz sand in one case, and crushed brick in the other. The test specimens had nominal dimensions of 40 × 40 × 160 mm and were tested in three-point bending after 7, 28, 90, and 300 days of maturation. From each composite, 3 specimens were tested and the compressive strength was determined from the 6 specimen parts that remained after the bending tests. The obtained flexural and compressive strength values for the abovementioned 4 composite ages were approximated by the exponential function , where the coefficient a represents a horizontal asymptote to the approximation curve, i.e. the theoretical strength of the composite at time t = ∞; the exponential term of the approximation with the coefficients b and c expresses the degree of the time-dependent change of the respective compressive strength in the interval t = (0, ∞). The approximation was performed with the least squares method using genetic algorithms implemented in the Java GA package with open source code.

Enhancing the Fire Resistance of Concrete Structures by Applying Fire-Retardant Temperature-Resistant Metal Coatings

The issues relating to an increase in the fire-resistance of concrete structures by applying (heat dissipating) fire-retardant and fire resistant metal coatings onto them was considered. The experimental investigation data obtained for the heating rate of the brick coated with the aluminum layer as heat dissipating coating were given. The investigation was carried out through the comparison of a time-dependent change in the temperature of the material coated with the aluminum layer with the temperature of uncoated material. The obtained research results proved a decrease in the heating rate of the coated brick exposed to the thermal irradiation.

RESEARCH ON PERSONALIZED RECOMMENDATION ALGORITHM FUSING TIME AND LOCATION

With development of recommendation systems, they are faced with more and more challenges. In order to relieve problems existing in commodity selection by users of different preferences from different regions, personalized recommendation based on location information has emerged. Nowadays most recommendation systems based on location information neglect the fact that users’ preference will change with time. To solve the above problem, geographic location and time factor of users are effectively combined in this paper, and a personalized recommendation algorithm TLPR combining time and location information is proposed. This algorithm determines the users’ geographic location according to postcode information of the users, uses pyramid quadtree model to distribute users into nodes at each layer in the pyramid, utilizes collaborative filtering algorithm for local recommendation in each node, introduces a time function to regulate time-dependent change of user interests when calculating user similarity at each node and finally realizes a comprehensive recommendation by distributing a weight for recommendation result at each layer in the pyramid quadtree. A comparative experience is carried out for recommendation performance of this algorithm on MovieLens dataset, and experimental results indicate that this algorithm is of better recommendation effect

Changes in the Syndesmotic Reduction After Syndesmotic Suture-Button Fixation for Ankle Malleolar Fractures: 1-Year Longitudinal Evaluations Using Computed Tomography

Background: Evaluation over time is important in assessing the reduction of the syndesmosis after suture-button fixation for ankle malleolar fractures. The purposes of this study were to evaluate time-dependent change in the syndesmotic reduction immediately after suture-button fixation for ankle malleolus fractures and 1 year after surgery using computed tomography, and to investigate the reliability of the measurement values to evaluate the reduction of syndesmosis. Methods: We assessed 28 patients who underwent suture-button fixation for ankle fractures. Syndesmotic reduction was assessed within 2 weeks of the fracture surgery and 1 year after surgery using axial computer tomographic images. Side-to-side differences in the anterior, central, and posterior tibiofibular distances, anteroposterior fibular translation, fibular rotation, and syndesmosis area were measured. Results: The mean anterior tibiofibular distance and anteroposterior fibular translation were 1.8 mm and 1.5 mm, respectively, after syndesmotic fixation. They decreased to 1.2 mm and 0.6 mm, respectively, at 1 year after surgery ( P = .03 and P = .01, respectively). The other measurement values did not change over time. The minimum detectable change in the distance of measurements was 1 mm or less. Conclusion: The anterior tibiofibular distance and anteroposterior fibular translation had decreased 1 year after fixation in ankle malleolar fractures with syndesmotic suture button. Even if the fibula is posteriorly malreduced by the time computed tomography is performed immediately after surgery, the fibula may return to a good position 1 year after surgery. Level of Evidence: Level IV, case series.