Mechanical Metamaterials for Handwritten Digits Recognition.

The increasing needs for new types of computing lie in the requirements in harsh environments. In this study, the successful development of a non-electrical neural network is presented that functions based on mechanical computing. By overcoming the challenges of low mechanical signal transmission efficiency and intricate layout design methodologies, a mechanical neural network based on bistable kirigami-based mechanical metamaterials have designed. In preliminary tests, the system exhibits high reliability in recognizing handwritten digits and proves operable in low-temperature environments. This work paves the way for a new, alternative computing system with broad applications in areas where electricity is not accessible. By integrating with the traditional electronic computers, the present system lays the foundation for a more diversified form of computing.

Physics-supervised deep learning-based optimization (PSDLO) with accuracy and efficiency.

Identifying efficient and accurate optimization algorithms is a long-desired goal for the scientific community. At present, a combination of evolutionary and deep-learning methods is widely used for optimization. In this paper, we demonstrate three cases involving different physics and conclude that no matter how accurate a deep-learning model is for a single, specific problem, a simple combination of evolutionary and deep-learning methods cannot achieve the desired optimization because of the intrinsic nature of the evolutionary method. We begin by using a physics-supervised deep-learning optimization algorithm (PSDLO) to supervise the results from the deep-learning model. We then intervene in the evolutionary process to eventually achieve simultaneous accuracy and efficiency. PSDLO is successfully demonstrated using both sufficient and insufficient datasets. PSDLO offers a perspective for solving optimization problems and can tackle complex science and engineering problems having many features. This approach to optimization algorithms holds tremendous potential for application in real-world engineering domains.

Electrical Interference Simulation and Prediction Model for Acoustoelectric Logging Detector.

Acoustic logging instruments generate high voltages in the order of thousands of volts. Electrical interferences are thus induced by high-voltage pulses that affect the logging tool and make it inoperable owing to damaged components in severe cases. High-voltage pulses from the acoustoelectric logging detector interfere with the electrode measurement loop through capacitive coupling, which has seriously affected the acoustoelectric signal measurements. In this paper, we simulate high voltage pulses, capacitive coupling and electrode measurement loops based on qualitative analysis of the causes of electrical interference. Based on the structure of the acoustoelectric logging detector and the logging environment, an electrical interference simulation and prediction model was developed to quantify the characteristics of the electrical interference signal.

Experimental Study on the Azimuthal-Transmitting Transducer of Acoustic Logging.

Azimuthal acoustic logging can survey the downhole formation more accurately, and the acoustic source is the crucial component of the downhole acoustic logging tool with azimuthal resolution characteristics. To realize downhole azimuthal detection, assembling multiple transmitting piezoelectric vibrators in the circumferential direction is necessary, and the performance of azimuthal-transmitting piezoelectric vibrators needs attention. However, effective heating test and matching methods are not yet developed for downhole multi-azimuth transmitting transducers. Therefore, this paper proposes an experimental method to comprehensively evaluate downhole azimuthal transmitters; furthermore, we analyze the azimuthal-transmitting piezoelectric vibrator parameters. This paper presents a heating test apparatus and studies the admittance and driving responses of the vibrator at different temperatures. The transmitting piezoelectric vibrators showing a good consistency in the heating test were selected, and an underwater acoustic experiment was performed. The main lobe angle of the radiation beam, horizontal directivity, and radiation energy of the azimuthal vibrators and azimuthal subarray are measured. The peak-to-peak amplitude radiated from the azimuthal vibrator and the static capacitance increase with an increase in temperature. The resonant frequency first increases and then decreases slightly with an increase in temperature. After cooling to room temperature, the parameters of the vibrator are consistent with those before heating. Hence, this experimental study can provide a foundation for the design and matching selection of azimuthal-transmitting piezoelectric vibrators.

Physical Simulation of Ultrasonic Imaging Logging Response.

Ultrasonic imaging logging can visually identify the location, shape, dip angle and orientation of fractures and holes. The method has not been effectively applied in the field; one of the prime reasons is that the results of physical simulation experiments are insufficient. The physical simulation of fracture and hole response in the laboratory can provide a reference for the identification and evaluation of the underground geological structure. In this work, ultrasonic scanning experiments are conducted on a grooved sandstone plate and a simulated borehole and the influence of different fractures and holes on ultrasonic pulse echo is studied. Experimental results show that the combination of ultrasonic echo amplitude imaging and arrival time imaging can be used to identify the fracture location, width, depth and orientation, along with accurately calculating the fracture dip angle. The evaluated fracture parameters are similar to those in the physical simulation model. The identification accuracy of the ultrasonic measurement is related to the diameter of the radiation beam of the ultrasonic transducer. A single fracture with width larger than or equal to the radiation beam diameter of the ultrasonic transducer and multiple fractures with spacing longer than or equal to the radiation beam diameter can be effectively identified.

Design of a New Seismoelectric Logging Instrument.

To increase the accuracy of reservoir evaluation, a new type of seismoelectric logging instrument was designed. The designed tool comprises the invented sonde-structured array complex. The tool includes several modules, including a signal excitation module, data acquisition module, phased array transmitting module, impedance matching module and a main system control circuit, which are interconnected through high-speed tool bus to form a distributed architecture. UC/OS-II was used for the real-time system control. After constructing the experimental measurement system prototype of the seismoelectric logging detector, its performance was verified in the laboratory. The obtained results showed that the consistency between the multi-channel received waveform amplitude and benchmark spectrum was more than 97%. The binary phased linear array transmitting module of the instrument can realize 0° to 20° deflection and directional radiation. In the end, a field test was conducted to verify the tool's performance in downhole conditions. The results of this test proved the effectiveness of the developed seismoelectric logging tool.

Anisotropic and gate-tunable valley filtering based on 8-Pmmn borophene.

We propose a valley filter based on 8-Pmmn borophene which hosts two tilted Dirac cones. It is found that the application of a magnetic-electric barrier provided by a single ferromagnetic gate is sufficient to create valley-polarized current in 8-Pmmn borophene. The valley polarization of output current depends on the barrier orientation. Due to an intrinsic symmetry, it vanishes when the barrier orientation is along the tilted direction of Dirac cones. For the barrier orientation perpendicular to the tilted direction, the valley polarization for a realistic magnetic barrier can approach nearly 100% at proper Fermi energy and gate voltage. The remarkable valley contrast of conductance in this case is attributed to a new transmission resonance. The tilting of Dirac cones is essential for the predicted valley filtering. Our findings are helpful for valleytronic applications of two-dimensional materials with tilted Dirac cones.

Intelligent Fault-Diagnosis System for Acoustic Logging Tool Based on Multi-Technology Fusion.

To improve the performance of acoustic logging tool in detecting three-dimensional formation, larger and more complicated transducer arrays have been used, which will greatly increase the difficulty of fault diagnosis during tool assembly and maintenance. As a result, traditional passive diagnostic methods become inefficient, and very skilled assemblers and maintainers are required. In this study, fault-diagnosis requirement for the acoustic logging tool at different levels has been analyzed from the perspective of the tool designer. An intelligent fault-diagnosis system consisting of a master-slave hardware architecture and a systemic diagnosis strategy was developed. The hardware system is based on the embedded technology, while the diagnosis strategy is built upon fault-tree analysis and data-driven methods. Diagnostic practice shows that this intelligent system can achieve four levels of fault diagnosis for the acoustic logging tool: System, subsystem, circuit board, and component. This study provided a more rigorous and professional fault diagnosis during tool assembly and maintenance. It is expected that this proposed method would be of great help in achieving cost reduction and improving work efficiency.

Ultrafast Excited-State Dynamics of V_{3}O_{5} as a Signature of a Photoinduced Insulator-Metal Phase Transition.

The ultrafast elastic light scattering technique is applied to reveal the strong nonlinearity of V_{3}O_{5} associated with a photoinduced insulator-metal phase transition. Observation of time-domain relaxation dynamics suggests several stages of structural transition. We discuss the nonequilibrium processes in V_{3}O_{5} in terms of photoinduced melting of a polaronic Wigner crystal, coalescence of V-O octahedra, and photogeneration of acoustical phonons in the low-T and high-T phases of V_{3}O_{5}. A molecular dynamics computation supports experimentally observed stages of V_{3}O_{5} relaxation dynamics.

Acoustic Emission and Echo Signal Compensation Techniques Applied to an Ultrasonic Logging-While-Drilling Caliper.

A logging-while-drilling (LWD) caliper is a tool used for the real-time measurement of a borehole diameter in oil drilling engineering. This study introduces the mechanical structure and working principle of a new LWD caliper based on ultrasonic distance measurement (UDM). The detection range is a major performance index of a UDM system. This index is determined by the blind zone length and remote reflecting interface detection capability of the system. To reduce the blind zone length and detect near the reflecting interface, a full bridge acoustic emission technique based on bootstrap gate driver (BGD) and metal-oxide-semiconductor field effect transistor (MOSFET) is designed by analyzing the working principle and impedance characteristics of a given piezoelectric transducer. To detect the remote reflecting interface and reduce the dynamic range of the received echo signals, the relationships between the echo amplitude and propagation distance of ultrasonic waves are determined. A signal compensation technique based on time-varying amplification theory, which can automatically change the gain according to the echo arrival time is designed. Lastly, the aforementioned techniques and corresponding circuits are experimentally verified. Results show that the blind zone length in the UDM system of the LWD caliper is significantly reduced and the capability to detect the remote reflecting interface is considerably improved.

Serine-arginine protein kinase 1 promotes a cancer stem cell-like phenotype through activation of Wnt/ß-catenin signalling in NSCLC.

Cancer stem cells (CSCs) are commonly associated with cancer recurrence and metastasis that occurs in up to 30-55% of non-small-cell lung carcinoma (NSCLC) patients. Herein, we showed that serine-arginine protein kinase 1 (SRPK1) was highly expressed at both the mRNA and the protein levels in human NCSLC. SRPK1 was associated with the clinical features of human NSCLC, including clinical stage (p < 0.001) and T (p = 0.001), N (p = 0.007), and M (p = 0.001) classifications. Ectopic overexpression of SRPK1 promoted the acquisition of a stem cell-like phenotype in human NSCLC cell lines cultured in vitro. Overexpression of SRPK1 increased sphere formation and the proportion of side-population cells that exclude Hoechst dye. Conversely, SRPK1 silencing reduced the number of spheres and the proportion of side-population cells. Mouse studies indicated that SRPK1 promoted NSCLC cell line tumour growth and SRPK1 overexpression reduced the number of tumour cells required to initiate tumourigenesis in vivo. Mechanistically, gene set enrichment analysis showed that Wnt/ß-catenin signalling correlated with SRPK1 mRNA levels and this signalling pathway was hyperactivated by ectopic SRPK1 expression in NSCLC cell lines. Immunofluorescence demonstrated that SRPK1 enhanced ß-catenin accumulation in the nuclei of NSCLC cell lines, and inhibition of ß-catenin signalling abrogated the SRPK1-induced stem cell-like phenotype. Together, our findings suggest that SRPK1 promotes a stem cell-like phenotype in NSCLC via Wnt/ß-catenin signalling. Moreover, SRPK1 may represent a novel target for human NSCLC diagnosis and therapy. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Inequalities in Cardiovascular Health Between Local and Migrant Residents: A Cross-Sectional Study of 6934 Participants in Longhua District, Shenzhen.

Household registration status is one social determinant that influences health disparities. This study aimed to investigate the disparities in cardiovascular health between local and migrant residents, which may provide important implications for public health services and may help improve cardiovascular health for residents in Shenzhen.A cross-sectional study was conducted in Shenzhen City Longhua district. Participants were selected for face-to-face interview surveys by using a multistage cluster random sampling design. Chi-square tests and multiple logistic regression models were constructed to compare cardiovascular health between the migrant and local residents.A total of 6934 eligible respondents, of whom 1400 were local and 5534 were migrants, completed the face-to-face interview surveys. The local residents were more likely to have hypertension (3.1% vs. 2.0%, P < 0.05) and diabetes mellitus (1.4% vs. 0.5%, P < 0.05), whilst to be overweight or obese (20.3% vs. 16.4%, P < 0.05) when compared with their migrant counterparts. A higher proportion of local residents than migrant ones had ≥2 cardiovascular risk factors, 2.4% and 1.2%, respectively (P < 0.01). Compared with migrants, the locals were more likely to know their BP values (65.4% vs. 54.5%, P < 0.05) and know the symptoms of diabetes (63.1% vs. 49.7%, P < 0.01).Our study suggests that household registration status is an important driver of social disparities in cardiovascular health except for the factors regarding socioeconomic status. Programs to improve the awareness of hypertension and diabetes are suggested to be initiated among the migrants.

Epidemiological investigation of suspected autism in children and implications for healthcare system: a mainstream kindergarten-based population study in Longhua District, Shenzhen.

BACKGROUND: Individuals with autism put a heavy demand on medical services, and prevalence estimates are needed for the planning of such services. Screening for autism in children has important implications for individuals and policy makers. This study aimed to estimate prevalence of suspected autism in children in Longhua District, Shenzhen, and to investigate risk factors for autism. METHODS: A cross-sectional study was conducted in Longhua District, Shenzhen in October 2014. A total of 141 kindergartens were approached and consented to participate in the current study. All children who met the inclusion criteria were screened for autism by using the Autism Behavior Checklist (ABC). RESULTS: 15,200 children in total completed the survey and were included in the final analysis. 2.6 % (95 % CI 2.3-2.9) respondents had a high probability of autism, while 4.0 % (95 % CI 3.7-4.3) respondents had questionable autism. Male children were more likely to develop autism when compared with their female counterparts (P < 0.001). Children of mothers with a lower education level and younger age tended to develop autism (P < 0.001). CONCLUSIONS: Our study shows a high prevalence rate of suspected autism in children which suggests an urgent need of early detection of autism with ABC across the Shenzhen city, or even around China. Further studies with diagnostic procedure are warranted. Maternal age and education level, and gender of children are possible factors related to autism.

Annular wave packets at Dirac points in graphene and their probability-density oscillation.

Wave packets in graphene whose central wave vector is at Dirac points are investigated by numerical calculations. Starting from an initial Gaussian function, these wave packets form into annular peaks that propagate to all directions like ripple-rings on water surface. At the beginning, electronic probability alternates between the central peak and the ripple-rings and transient oscillation occurs at the center. As time increases, the ripple-rings propagate at the fixed Fermi speed, and their widths remain unchanged. The axial symmetry of the energy dispersion leads to the circular symmetry of the wave packets. The fixed speed and widths, however, are attributed to the linearity of the energy dispersion. Interference between states that, respectively, belong to two branches of the energy dispersion leads to multiple ripple-rings and the probability-density oscillation. In a magnetic field, annular wave packets become confined and no longer propagate to infinity. If the initial Gaussian width differs greatly from the magnetic length, expanding and shrinking ripple-rings form and disappear alternatively in a limited spread, and the wave packet resumes the Gaussian form frequently. The probability thus oscillates persistently between the central peak and the ripple-rings. If the initial Gaussian width is close to the magnetic length, the wave packet retains the Gaussian form and its height and width oscillate with a period determined by the first Landau energy. The wave-packet evolution is determined jointly by the initial state and the magnetic field, through the electronic structure of graphene in a magnetic field.

Electronic transport properties of coupled quantum dots on carbon nanotubes.

We investigate the electronic transport properties of coupled quantum dots, controlled by local gates on carbon nanotubes. The inter-dot coupling can be tuned from weak to strong by changing gate voltages, and oscillates in short and long period with the distance between two gates. We introduce a one-dimensional scattering model to describe the mechanism of the electron transport through the carbon nanotube quantum dots. We show that pi and PI* channels contribute differently to the inter-dot coupling and the transport phase plays a key role in the oscillations of the coupling.

Nucleotide capacitance calculation for DNA sequencing.

Using a first-principles linear response theory, the capacitance of the DNA nucleotides, adenine, cytosine, guanine, and thymine, are calculated. The difference in the capacitance between the nucleotides is studied with respect to conformational distortion. The result suggests that although an alternate current capacitance measurement of a single-stranded DNA chain threaded through a nanogap electrode may not be sufficient to be used as a standalone method for rapid DNA sequencing, the capacitance of the nucleotides should be taken into consideration in any GHz-frequency electric measurements and may also serve as an additional criterion for identifying the DNA sequence.

Standing Friedel waves: a quantum probe of electronic states in nanoscale devices.

We report a theoretical study of the dynamic response of electrons in a metallic nanowire or a two-dimensional electron gas under a capacitively coupled "spot gate" driven by an ac voltage. A dynamic standing Friedel wave (SFW) is formed near the spot gate and near edges and boundaries, analogous to the static Friedel oscillations near defects. The SFW wavelength is controlled by the ac voltage frequency and the device's Fermi velocity, whereby the latter can be measured. In addition, the SFW amplitude exhibits resonant behavior at driving frequencies that are related to eigenenergy spacings in the device, allowing their direct measurement.

Random-walk statistics in moment-based O(N) tight binding and applications in carbon nanotubes.

A computational framework for a moment-based O(N) tight-binding atomistic method is presented, analyzed, and applied to the problem of electronic properties of deformed carbon nanotubes, where N is the number of atoms in the system. The moment-based approach is based on the maximum entropy and kernel polynomial methods for constructing the electronic density of states from local statistical information about the environment around individual atoms. Random-walk statistics are formally presented as the basis for several methods to collect the moments of the density of states in a computationally efficient manner. The computational complexity and accuracy of these methods are systematically analyzed. Using these methods for the problem of deformed carbon nanotubes, it is shown that the computational cost for some cases, per atom, scales as efficiently as O(M log M), where M is the desired number of moments in the expansion of the density of states. These methods are compared to other methods such as direct diagonalization and a Green's function approach.