Physical Characteristics of Welding Arc Ignition Process

The existing research of welding arc mainly focuses on the stable combustion state and the research on the mechanism of welding arc ignition process is quite lack.The tungsten inert gas（TIG） touch arc ignition process is observed via a high speed camera and the high time resolution spectral diagnosis system.The changing phenomenon of main ionized element provided the electrons in the arc ignition is found.The metallic element is the main contributor to provide the electrons at the beginning of the discharging,and then the excitated shielding gas element replaces the function of the metallic element.The electron density during the period of the arc ignition is calculated by the Stark-broadened lines of Hα.Through the discussion with the repeatability in relaxation phenomenon,the statistical regularity in the arc ignition process is analyzed.The similar rules as above are observed through the comparison with the laser-assisted arc ignition experiments and the metal inert gas（MIG） arc ignition experiments.This research is helpful to further understanding on the generation mechanism of welding arc ignition and also has a certain academic and practical significance on enriching the welding physical theoretical foundation and improving the precise monitoring on automatic arc welding process.

Analysis of a Group of Weak Small-Scale Vortexes in the Planetary Boundary Layer in the Mei-yu Front

A mei-yu front process in the lower reaches of the Yangtze River on 23 June 1999 was simulated by using the fifth-generation Pennsylvania State University-NCAR （PSU/NCAR） Mesoscale Model （MM5） with FDDA （Four Dimension Data Assimilation）. The analysis shows that seven weak small mesoscale vortexes of tens of kilometers, correspondent to surface low trough or mesoscale centers, in the planetary boundary layer （PBL） in the mei-yu front were heavily responsible for the heavy rainfall. Sometimes, several weak small-scale vortexes in the PBL could form a vortex group, some of which would weaken locally, and some would develop to be a meso-α-scale low vortex through combination. The initial dynamical triggering mechanism was related to two strong currents： one was the northeast flow in the PBL at the rear of the mei-yu front, the vortexes occurred exactly at the side of the northeast flow; and the other was the strong southwest low-level jet （LLJ） in front of the Mei-yu front, which moved to the upper of the vortexes. Consequently, there were notable horizontal and vertical wind shears to form positive vorticity in the center of the southwest LLJ. The development of mesoscale convergence in the PBL and divergence above, as well as the vertical positive vorticity column, were related to the small wind column above the nose-shaped velocity contours of the northeast flow embedding southwestward in the PBL, which intensified the horizontal wind shear and the positive vorticity column above the vortexes, baroclinicity and instability.

Analysis of Rainstorm Process in a Single Station on July 19, 2010

[Objective] The aim was to study the rainstorm process in a single station on July 19, 2010. [Method] Based on MICAPS conventional data and Doppler radar data, the rainstorm process in Dagang station in Tianjin on July 19, 2010 was analyzed systematically by means of weather dynamic diagnosis analysis. [Result] From physical vector diagnostic analysis, the dynamic effect provided by southwest vortex and warm shear line, water vapor transported by warm and wet flow at the edge of subtropical high and upper and lower jet and unstable convection of atmospheric stratification were the main causes of rainstorm formation on July 19, 2010. In addition, rainfall area was located in the big convergence area of vapor flux, and there was a negative center of vapor flux divergence before rainfall, with obvious accumulation of water vapor, which provided better water vapor condition for this rainstorm. [Conclusion] The study could provide theoretical foundation for the forecast of rainstorm in Tianjin.

Differential diagnosis of cervical radiculopathy and superior pulmonary sulcus tumor

Background The result would be disastrous if the superior pulmonary sulcus tumor （Pancoast tumor） was misdiagnosed as degenerative cervical spine diseases. The aim of this study was to investigate the differential diagnosis methods of cervical radiculopathy and superior pulmonary sulcus tumor. Methods Clinical manifestations, physical, and radiological findings of 10 patients, whose main complaints were radiating shoulder and arm pain and later were diagnosed with superior pulmonary sulcus tumor, were reviewed and compared with those of cervical radiculopathy. Results Superior pulmonary sulcus tumor patients have shorter mean history and fewer complaints of neck pain or limitation of neck movement. Physical examination showed almost normal cervical spine range of motion. Spurling＇s neck compression test was negative in all patients. Anteroposterior cervical radiographs showed the lack of pulmonary air at the top of the affected lung in all cases and first rib encroachment in one case. The diagnosis of superior pulmonary sulcus tumor can be further confirmed by CT and MRI. Conclusions By the method of combination of history, physical examination, and radiological findings, superior pulmonary sulcus tumor can be efficiently differentiated from cervical radiculopathy. Normal motion range of the cervical spine, negative Spurling＇s neck compression test, and the lack of pulmonary air at the top of the affected lung in anteroposterior cervical radiographs should be considered as indications for further chest radiograph examinations.