No abstract

A new method of wireless data telemetry used by oil industry uses compressional acoustic waves to transmit downhole information from the bottom hole to the surface. Unfortunately, acoustic echoes and drilling vibration noises in periodic drillstring are a major issue in transmission performance. A combined acoustic echo and noise suppression method based on wave motion characteristic in drillstring is adopted to enhance an upward-going transmitted acoustic signal. The presented scheme consists of a primary acoustic echo canceller using an array of two accelerometers for dealing with the downward-going noises and a secondary acoustic insulation structure for restraining the upward-going vibration noises. Furthermore, the secondary acoustic insulation structure exhibits a banded and dispersive spectral structure because of periodic groove configuration. By using a finite-differential algorithm for the one-dimensional propagation of longitudinal waves, acoustic receiving characteristics of transmitted signals are simulated with additive Gaussian noise in a periodic pipe structure of limited length to investigate the effects on transmission performance optimization. The results reveal that the proposed scheme can achieve a much lower error bit ratio over a specified acoustic isolation frequency range with a 30–40 dB reduction in the average noise level compared to traditional single-receiver scheme.

In the oil industry, the accompanied reverberation is a major constraint in the transmission rate and distance because the drillstring is a heterogeneous assembly. Based on the transient impulse responses in uplink and downlink channels, an improved simplified echo suppression model with two acoustic receivers is presented in consideration of position optimization of single acoustic receiver. Then the acoustic receiving characteristics of transmitted signals in a length-limited periodic drillstring channel are obtained in single-and dual-receiver modes. An additive downward white Gaussian noise is also introduced in the channel. Moreover, an experimental rig is established by using a rotatable electromagnetic vibration exciter and two piezoelectric accelerometers, which are spaced one-quarter wavelength apart along a 6.3-meter simulated periodic drillstring. The ASK-, FSK-, and PSK-modulated square-wave pulse sequences at a transmission rate of 200 bit/s are applied to the simulated drillstring at a rotation speed of 0, 80, and 140 r/min, respectively. The experimental results show that the dual-receiver mode can exhibit a significantly improved average error bit ratio, which is approximately 2.5 to 3 times lower than that of the single-receiver mode, especially under the conditions of higher rotation speeds.

Online drug sales are booming nowadays, and online sales of some prescription drugs are no longer prohibited by law, following over-the-counter ones. Because of its particularity, prescription drugs must be used according to doctor's prescription to ensure their safety.In order to explore the illegal aspects in the current online prescription drug sales, the authors took three cases as the perspective and found out the following problems: Firstly, some online doctors do not hold valid certificates of medical practice; Secondly, doctors carry out first-diagnosis activities in violation of Internet Diagnosis and Treatment Management Measures; Thirdly, doctors do not follow the technical operation specifications, resulting in the diagnosis and treatment services are not compliant; Fourthly, doctors prescribe prescriptions in violation of the Prescription Management Measures. In addition, after the emergence of medical disputes, the responsibilities among online platforms, Internet hospitals and the physical medical institutions relied on are not clear, which is very detrimental to the rights protection of patients. The above problems seriously deviate from the safety principles that prescription drugs should follow. To study the current illegality of the current online prescription drug sales process, the author take the form of cases to carry out legal analysis. Furthermore, the authors hope that this analysis can attract the attention of the medicine, law, business and competent departments, so as to protect the basic human health rights of drug users right.