Groundwater velocity has significant effects on the formation of a frozen curtain during freezing. In order to study the influence of the velocity on a frozen curtain, a large physical model test ...platform was established for double-pipe freezing. Based on this platform, freezing tests for different velocities were carried out. Quartz sand was selected as a similar material. The freezing temperature of the saturated sand layer was found by analyzing the results of the nuclear magnetic resonance (NMR). Based on the study of the thermal physical properties of the sand layer, the freezing test results were analyzed, and the results showed that the flow led to the differential development of the temperature between the upstream and downstream sections of the freezing pipes. Moreover, the larger the velocity, the greater the difference. The flow prolonged the overlapping time of the frozen curtains. Additionally, the flow slowed down the development of the frozen curtain area and the frozen curtain thickness. The larger the flow velocity, the greater the inhibition of the flow on the development of the frozen curtain. The test results can provide more references for the design and construction of freezing engineering with flowing groundwater.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The fifth generation (5G) mobile communication network is expected to accommodate the communication requirements of billions of connected devices by enhancing speed, latency, size and cost. ...Millimeter wave (mmW) technology a candidate 5G technology requires special and well-designed antennas to power its transmissions. Microstrip patch antennas (MPA), which are popular due to their low profile, lightweight, tiny size, low cost, and simple fabrication, could meet these requirements. The proposed MPA is designed and fabricated on a Rogers RT Duroid 5880 substrate with a dimension of 6.3 × 7.24 × 0.5 mm 3 , a dielectric constant of 2.2 and a tangent loss of 0.0009. The proposed MPA at 28 GHz with a measured return loss of -21.37 dB, measured impedance bandwidth of 2.685 GHz and directivity of 10.02 dBi. The proposed antenna has significantly improved gain and bandwidth as compared with the previous literature due to its compact size which can be used for 5G mobile communication.
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