Variation characteristics of temperature and moisture content of seasonal frozen soil during freezing process in Changchun,China

In China, seasonal frozen soil is widely distributed. The freezing damage of subgrade soil in Jilin Province has been one of major engineering geological problems troubling the safety of road, in which some common damage phenomena, such as frost heave, subsidence deformation and frost boiling, are all caused by water translocation. Aiming at the phenomenon, the changes of moisture content of seasonal frozen soil in Changchun City are mainly studied by long-term field observation and indoor testing of physical properties under different conditions, and then the variation characteristics of moisture content in soil under different compactness and temperature conditions are realized. The results show that the increasing section of moisture content and negative temperature section all lie in O. 0 - 1.0 m of subgrade. Both lowest air and earth temperature occur in January to February, and the most negative temperature ranges from -7℃ to -10℃.

Isolation and denitrification characteristic of an aerobic denitrifier

Aerobic denitrifiers were enriched by activated sludge cultivation method. By this way, 105 strains were isolated from the activated sludge and 25 strains were confirmed to be capable of obtaining energy by deoxidization of nitrate to nitrogen gas under aerobic condition. The characteristic of one denitrifier, Pseudomonas chloritidismutans strain, was particularly studied due to its higher nitrogen removal rate. It was found that Pseudumonas chloritidismutans can use nitrite, nitrate and oxygen for aerobic respiration in liquid medium, and tbe pH increased and ORP decreased by activated denitrifier. When they used nitrite or nitrate fur respiration, nitrogen removal effect was high and nitrite could be reduced more efficiently than nitrate. Denitrification process was accomplished faster when both nitrite and nitrate existed in the medium compared to each of which existed alone. Particularly, at denitrifying activity, the nitrogen removal rate of strain was not affected by the DO concentration in the euhure media.

Comparative study on combined preoxidation by potassium permanganate composites with chlorine and preozonation for enhancing coagulation

Comparative pilot tests were conducted to investigate the coagulation-aid effects of the combined preoxidation by potassium permanganate composites （PPC） with chlorine and preozonation. And the synergistie mechanism of combined preoxidation was discussed. Results showed that 1.0 mg/L PPC with 2. 0 mg/L chlorine could further improve the quality of treated water, as indicated by residual turbidity, TOC and algae. The enhanced efficiency could be explained by the synergistic effect of the preoxidants themselves, or the effect of chlorine and the intermediate such as hydrous manganese dioxide, which was generated by potassium permanga- nate, the main ingredient of PPC.

Application of TSD tunnel seismic prediction system in karst area

TSD is one of the classical methods of tunnel seismic prediction based on higher accuracy multi-wave multi-component seismology.The working principle of the TSD and an application example of the TSD on tunnel prediction in Chongqing are introduced in this paper.This system has two ports for speed signal and acceleration signal,and the equipment is more portable and easy to use.According to the application results we can conclude that the TSD prediction system is accurate and it has the wide application prospect in tunnel seismic detection.

Application of ultrasonic CT method in nondestructive detection of interior defects in large scale concrete structural member of bridge

The ultrasonic computed tomography （USCT） method is derived from the basic principles of X-ray section scanning. This method records the arriving times of ultrasonic wave between the probes and the sources to ealculate the elastic wave velocity values in the section using the arrival times. Through analyzed the distribution Of elastic wave velocity in aim area, the information of the strength and the homogeneity of the investigated zone could be got indirectly. The authors introduced the operational principle of USCT and a practical case of using this method to detect the interior defects in large scale concrete structural member. Compared with other exploration methods, this method is more efficient and accurate.

Enhanced catalytic oxidation of 2,4-dichlorophenol via singlet oxygen dominated peroxymonosulfate activation on CoOOH@Bi_(2)O_(3)composite

Cobalt oxyhydroxide(CoOOH)has been turned out to be a high-efficiency catalyst for peroxymonosulfate(PMS)activation.In this study,CoOOH was loaded on bismuth oxide(Bi_(2)O_(3))using a facile chemical precipitation process to improve its catalytic activity and stability.The result showed that the catalytic performance on the 2,4-dichlorophenol(2,4-DCP)degradation was significantly enhanced with only 11 wt%Bi_(2)O_(3)loading.The degradation rate in the CoOOH@Bi_(2)O_(3)/PMS system(0.2011 min−1)was nearly 6.0 times higher than that in the CoOOH/PMS system(0.0337 min−1).Furthermore,CoOOH@Bi_(2)O_(3)displayed better stability with less Co ions leaching(16.4%lower than CoOOH)in the PMS system.These phenomena were attributed to the Bi_(2)O_(3)loading which significantly increased the conductivity and specific surface area of the CoOOH@Bi_(2)O_(3)composite.Faster electron transfer facilitated the redox reaction of Co(III)/Co(II)and thus was more favorable for reactive oxygen species(ROS)generation.Meanwhile,larger specific surface area furnished more active sites for PMS activation.More importantly,there were both non-radical(^(1)O_(2))and radicals(SO_(4)^(−)•,O_(2)^(−)•,and OH•)in the CoOOH@Bi_(2)O_(3)/PMS system and^(1)O_(2)was the dominant one.In general,this study provided a simple and practical strategy to enhance the catalytic activity and stability of cobalt oxyhydroxide in the PMS system.