Modelling of steady motion of solid specimens conveyed by travelling wave ultrasonic feeding

On the basis of the research on the morphology of the contact surfaces, a contact model is proposed, which regards the rough contact surfaces as the collections of elastic micro peaks. These micro peaks generate elastic contact force due to elastic deformation and the contact force has relationship to the morphology of the contact surfaces, the motion of the vibrator as well as the materials of the specimen and the vibrator. And using Newton’s second law to the specimen’s motion, the normal dynamical equation for the specimen with the actuation of the ultrasonic vibrator is established. Solving the dynamical equation, the normal kinetic function of specimen and the normal elastic contact force are obtained. Furthermore, the normalized contact time could be analyzed theoretically, which is defined as the ratio of contact time to period. The calculated results indicate that the normalized contact time decreases with the vibrator’s normal amplitude increasing, and increases with the standard deviation of the height of micro peaks on the contact surfaces. Finally, the average tangential velocity of the specimen, conveyed by a travelling wave ultrasonic feeding device, is discussed on the basis of the research on the normalized contact time. The formula of the specimen’s average tangential velocity is derived and it is the function of the normalized contact time, the tangential amplitude, the angular frequency and the phase difference of the tangential and the normal vibrations. Using this formula, the tangential velocity of the specimen is theoretically analyzed; in addition, the theoretical conclusions are compared with the experimental data

Psychological contract’s effect on job mobility: Evidence from Chinese construction worker

The subject of this study is that the psychological contract (PC) approaches to job mobility within the construction industry with special reference to migrant construction workers in China. Using a semi-structured interview to elicit a full range of the PC’s con- tent of construction worker, we unravel the mechanism of such contract to influence the informal job mobility of workers through the lens of the evolutionary game framework. The results demonstrate that, in the case of fulfilling PC, the informal job mobility of workers is under control, and both workers and employers benefit from this situation. This study deepens the understanding of the PC’s effect on the job mobility of construction workers in China during the course of economic change. The theoretical and practical implications are discusse

Microwave-to-optical conversion using lithium niobate thin-film acoustic resonators

Acoustic or mechanical resonators have emerged as a promising means to mediate efficient microwave-to-optical conversion. Here, we demonstrate conversion of microwaves up to 4.5 GHz in frequency to 1500 nm wavelength light using optomechanical interactions on suspended thin-film lithium niobate. Our method uses an interdigital transducer that drives a freestanding 100 μm-long thin-film acoustic resonator to modulate light traveling in a Mach–Zehnder interferometer or racetrack cavity. The strong microwave-to-acoustic coupling offered by the transducer in conjunction with the strong photoelastic, piezoelectric, and electro-optic effects of lithium niobate allows us to achieve a half-wave voltage of Vπ = 4.6 V and Vπ = 0.77 V for the Mach–Zehnder interferometer and racetrack resonator, respectively. The acousto-optic racetrack cavity exhibits an optomechanical single-photon coupling strength of 1.1 kHz. To highlight the versatility of our system, we also demonstrate a microwave photonic link with unitary gain, which refers to a 0 dB microwave power transmission over an optical channel. Our integrated nanophotonic platform, which leverages the compelling properties of lithium niobate, could help enable efficient conversion between microwave and optical fields

Net volatilization of PAHs from the North Pacific to the Arctic Ocean observed by passive sampling

The North Pacific-Arctic Oceans are important compartments for semi-volatile organic compounds’ (SVOCs) global marine inventory, but whether they act as a “source or sink” remains controversial. To study the air-sea exchange and fate of SVOCs during their poleward long-range transport, low-altitude atmosphere and surface seawater were measured for polycyclic aromatic hydrocarbons (PAHs) by passive sampling from July to September in 2014. Gaseous PAH concentrations (0.67–13 ng m−3) were dominated by phenanthrene (Phe) and fluorene (Flu), which displayed an inverse correlation with latitude, as well as a significant linear relationship with partial pressure and inverse temperature. Concentrations of PAHs in seawater (1.8–16 ng L−1) showed regional characteristics, with higher levels near the East Asia and lower values in the Bering Strait. The potential impact from the East Asian monsoon was suggested for gaseous PAHs, which – similar to PAHs in surface seawater - were derived from combustion sources. In addition, the data implied net volatilization of PAHs from seawater into the air along the entire cruise; fluxes displayed a similar pattern to regional and monthly distribution of PAHs in seawater. Our results further emphasized that air-sea exchange is an important process for PAHs in the open marine environments

The effect of 17β-estradiol-DNA adducts on the replication of exon # 5 of the human suppressor gene p53

AbstractUsing a PCR technique, exon # 5 of the human tumor suppressor gene p53 was amplified and ligated into the pCRII vector and transformed into Escherichia coli INVαF’ competent cells. The cloned exon # 5 was 184 bp long. Evidence is presented to show that after dimethyldioxirane epoxidation, 17β-estradiol was able to form 17β-estradiol-DNA adducts and to strongly inhibit the replication of the cloned exon # 5 producing smaller sizes of DNA fragments and introducing errors of incorporation at the 3′-end of the terminating DNAs. The errors occurred mainly at the clusters of the complementary ‘G’ and ‘A’ bases on the template strand DNA, presumably, the major sites where the 17β-estradiol-DNA adducts were formed

Over 300-km Transmission of 25 Gb/s Optical SSB NPAM-4 Signal with Electronic Dispersion Pre-compensation and Interference Mitigation

We experimentally demonstrate the interference mitigation in direct-detection of optical SSB signals with Nyquist-PAM-4. At 25 Gb/s, we achieve over 300-km and 500-km SSMF with an average BER of 2.7×10-3 (<HD-FEC) and 9.4×10-3 (<SD-FEC), respectively