Effect of discrete fibre reinforcement on soil tensile strength

The tensile behaviour of soil plays a significantly important role in various engineering applications. Compacted soils used in geotechnical constructions such as dams and clayey liners in waste containment facilities can suffer from cracking due to tensile failure. In order to increase soil tensile strength, discrete fibre reinforcement technique was proposed. An innovative tensile apparatus was developed to deter- mine the tensile strength characteristics of fibre reinforced soil. The effects of fibre content, dry density and water content on the tensile strength were studied. The results indicate that the developed test apparatus was applicable in determining tensile strength of soils. Fibre inclusion can significantly in- crease soil tensile strength and soil tensile failure ductility. The tensile strength basically increases with increasing fibre content. As the fibre content increases from 0% to 0.2%, the tensile strength increases by 65.7%. The tensile strength of fibre reinforced soil increases with increasing dry density and decreases with decreasing water content. For instance, the tensile strength at a dry density of 1.7 Mg/m^3 is 2.8 times higher than that at 1.4 Mg/m^3. It decreases by 30% as the water content increases from 14.5% to 20.5%. Furthermore, it is observed that the tensile strength of fibre reinforced soil is dominated by fibre pull-out resistance, depending on the interracial mechanical interaction between fibre surface and soil matrix.

Control Effects of Different Densities of Chemical Pheromones against Tobacco Cutworm Moth ( Spodoptera litura)

[ Objective ] The paper was to study the most suitable density of chemical pheromone to control Spodoptera litura in tobacco fields. [ Method ] Sixteen traps （ 4 lines x 4 rows） were placed according to the specifications of 25. 8 m ×25.8 m （ 15. 0 trap/hm2 ）, 31. 6 m× 31.6 m （ 10.0 trap/hm2 ） and 36.5 m × 36.5m （ 7.5 trap/hm2 ）. Meanwhile, a control area larger than 2 hm2 was set up with three repetitions. [ Result] Without consideration of impact of wind direc- tion, the amount of trapping moth increased with the increasing controlled area of single trap, but difference of trapping amount of moth was not significant under three different density treatments. Three placement densities could effectively control S. liture in tobacco fields, thereby reduce the use of pesticides and protect the natural enemies and reduce the control cost. [Conclusion] The suitable density of chemical pheromone traps to control S. litura was 31. 6 m x31. 6 m （10.0 trap/hm2 ）.

Global analysis of daily new COVID-19 cases reveals many staticphase countries including the United States potentially with unstoppable epidemic

BACKGROUND The coronavirus disease 2019(COVID-19)pandemic is hitting many countries.It is hypothesized the epidemic is differentially progressing in different countries.AIM To investigate how the COVID-19 epidemic is going on in different countries by analyzing representative countries.METHODS The status of COVID-19 epidemic in over 60 most affected countries was characterized.The data of daily new cases of each country were collected from Worldometer.The data of daily tests for the United States,Italy,and South Korea were collected from the Website of One World Data.Levels of daily positive COVID-19 tests in the two most affected states of the United States(New York and New Jersey)were collected from the website of the COVID Tracking Project.Statistics were analyzed using Microcal Origin software with ANOVA algorithm,and significance level was set at a P value of 0.05.RESULTS The COVID-19 epidemic was differentially progressing in different countries.Comparative analyses of daily new cases as of April 19,2020 revealed that 61 most affected countries can be classified into four types:Downward(22),upward(20),static-phase(12),and uncertain ones(7).In particular,the 12 static-phase countries including the United States were characterized by largely constant numbers of daily new cases in the past over 14 d.Furthermore,these static-phase countries were overall significantly lower in testing density(P=0.016)but higher in the level of positive COVID-19 tests than downward countries(P=0.028).These findings suggested that the testing capacity in static-phase countries was lagging behind the spread of the outbreak,i.e.,daily new cases(confirmed)were likely less than daily new infections and the remaining undocumented infections were thus still expanding,resulting in unstoppable epidemic.CONCLUSION Increasing the testing capacity and/or reducing the COVID-19 transmission are urgently needed to stop the potentially unstoppable,severing crisis in static-phase countries.