TIGS: An Inference Algorithm for Text Infilling with Gradient Search

Text infilling is defined as a task for filling in the missing part of a sentence or paragraph, which is suitable for many real-world natural language generation scenarios. However, given a well-trained sequential generative model, generating missing symbols conditioned on the context is challenging for existing greedy approximate inference algorithms. In this paper, we propose an iterative inference algorithm based on gradient search, which is the first inference algorithm that can be broadly applied to any neural sequence generative models for text infilling tasks. We compare the proposed method with strong baselines on three text infilling tasks with various mask ratios and different mask strategies. The results show that our proposed method is effective and efficient for fill-in-the-blank tasks, consistently outperforming all baselines.Comment: The 57th Annual Meeting of the Association for Computational Linguistics (ACL 2019

Time Reversal Method for Arch Bridge Cables Inspection using Longitudinal Guided Waves

Arch bridge cables consist of anchor heads, steel wires parallel arranged in an equilateral hexagon and hot-extruding PE sheathing layers outside the wires. The complex structure and contact force between wires aggravates the dispersion and attenuation of guided waves in steel wires. In order to reduce the attenuation of acoustical energy, below 80kHz low-frequency longitudinal guided waves is usually adopted. Low-frequency guided waves attenuate more slowly than high-frequency waves, but the received signal packets are wider and less recognizable. In this paper, the process of the time reversal method[1] is presented and the related parameters are calculated. Over a wide frequency range, using narrow-band pulse signals with different center-frequencies to drive comb-like magnetostrictive transducer array round the cable, extract the echo signals, which contains some feature information such as flaws, anchor heads, structural noise caused by contact force between wires. By taking advantage of the time-space compression characteristics of the method, the identification of anchor heads and flaws can be improved effectively and noise can also be decreased by driving the transducers again with the time reversed signal. Verification experiments show that the acoustical energy of guided waves can be focused on the position of flaws and the amplitude of flaws echo waves can be increased. At severe dispersion frequency, time reversal focusing process can improve the signal-noise ratio and suppress dispersion phenomenon caused by structural contact force

Magnetostrictive Helical Array Transducers for Inspecting Spiral Welded Pipes Using Torsional Flexural Waves

Wavefront analysis indicates that a flexural wave propagates at a helix angle with respect to the pipe axis. The expression for calculation of the helix angle for each flexural mode is given, and the helix angle dispersion curves for flexural modes are calculated. According to the new understanding of flexural guided waves, a magnetostrictive helical array transducer (MHAT) is proposed for selectively exciting a single predominant flexural torsional guided wave in a pipe and inspecting spiral welded pipes using flexural waves. A MHAT contains a pre-magnetized magnetostrictive patch that is helically coupled with the outer surface of a pipe, and an array of novel compound comb coils that are wrapped around the helical magnetostrictive patch. The proposed wideband MHAT possesses the direction control ability. A verification experiment indicates that flexural torsional mode T(3,1) at center frequency f=64kHz is effectively actuated by a MHAT with 13-degree helix angle. A 20-degree MHAT is adopted to inspect a spiral welded pipe, an artificial notch with cross section loss CSL=2.7% is effectively detected by using flexural waves

Anti-diabetic activity of aqueous extract of Fructus Ligustri Lucidi in a rat model of type 2 diabetes

Purpose: To determine the anti-diabetic activity of an aqueous extract of Fructus Ligustri Lucidi (FLL) in a rat model of type 2 diabetes (T2D).Method: Body weight (BW), food intake (FI), fasting blood glucose (FBG), glucose tolerance testing and insulin tolerance testing were used to determine the anti-diabetic activity of an aqueous extract of Fructus Ligustri Lucidi (FLL) in a rat model of streptozotocin-induced T2D. Anti-oxidant activity and oxidative stress were assessed by superoxide dismutase (SOD) and malondialdehyde (MDA) analyses, respectively.Results: Following FLL extract treatment, diabetic rat BW increased, while FI and FBG levels decreased. FLL extract increased glucose tolerance and decreased insulin tolerance. Following treatment with 300 and 600 mg/kg FLL extract, MDA levels reached 13.5 ± 0.9 nmol/ml and 13.8 ± 1.1 nmol/ml, respectively. Compared to MDA levels of 19.5 ± 1.1 nmol/ml in diabetic control group, MDA levels was decreased by 30.8 % and 29.0 % after the treatment with 300 and 600 mg/kg FLL extract, respectively, indicating alleviated oxidative stress.Conclusion: The results show that aqueous FLL extract has the potential to alleviate T2D, resulting in reduced FI and FBG, and increased BW. The anti-diabetic activity of FLL extract on T2D may be relevant to reduced oxidative stress burden.Keywords: Fructus Ligustri Lucidi, Type 2 diabetes, Anti-oxidant activity, Glucose tolerance, Insulin tolerance, Anxiety-like behaviou

Strain-induced semiconductor to metal transition in MA2Z4 bilayers

Very recently, a new type of two-dimensional layered material MoSi2N4 has been fabricated, which is semiconducting with weak interlayer interaction, high strength, and excellent stability. We systematically investigate theoretically the effect of vertical strain on the electronic structure of MA2Z4 (M=Ti/Cr/Mo, A=Si, Z=N/P) bilayers. Taking bilayer MoSi2N4 as an example, our first principle calculations show that its indirect band gap decreases monotonically as the vertical compressive strain increases. Under a critical strain around 22%, it undergoes a transition from semiconductor to metal. We attribute this to the opposite energy shift of states in different layers, which originates from the built-in electric field induced by the asymmetric charge transfer between two inner sublayers near the interface. Similar semiconductor to metal transitions are observed in other strained MA2Z4 bilayers, and the estimated critical pressures to realize such transitions are within the same order as semiconducting transition metal dichalcogenides. The semiconductor to metal transitions observed in the family of MA2Z4 bilayers present interesting possibilities for strain-induced engineering of their electronic properties

Resolved Raman sideband cooling of a single optically trapped cesium atom

We developed a resolved Raman sideband cooling scheme that can efficiently prepare a single optically trapped cesium (Cs) atom in its motional ground states. A two-photon Raman process between two outermost Zeeman sublevels in a single hyperfine state is applied to reduce the phonon number. Our scheme is less sensitive to the variation in the magnetic field than the commonly used scheme where the two outermost Zeeman sublevels belonging to the two separate ground hyperfine states are taken. Fast optical pumping with less spontaneous emission guarantees the efficiency of the cooling process. After cooling for 50 ms, 82% of the Cs atoms populate their three-dimensional ground states. Our scheme improves the long-term stability of Raman sideband cooling in the presence of magnetic field drift and is thus suitable for cooling other trapped atoms or ions with abundant magnetic sublevels.Comment: 4 pages, 3 figures, 1 tabl