Desertification and Blown Sand Disaster in China

Approximately 331 million ha, one-third of China＇s total land, is prone to desertification processes, leading to natural disasters and economic losses. In this study, the situation, tendency, their influences and their risk governance of desertification and blown sand disaster in China were examined using satellite images, field photographs, field data and a literature review. The desiccated areas in Lop Nor and the lower Heihe River fluvial plain covered about 50,000 km2 and 40,000 km2, respectively. In Ejina, about 100 species of vegetation became extinct. The rate of wind erosion in China was between 1,000 tons/km2/year and 2,000 tons/km2/year. There were 12 sand deserts and sandy lands, occupying a total of 710,000 km2. Salinized soils occurred across 99.1 million ha. The two main sand and dust storm-prone areas in China were the Tarim Basin and its surroundings, and the Alxa Plateau and its surroundings. From 1981 to 2007, the annual average frequency of sand and dust storms varied from 1 d to 37 d with a general increase from southeast to northwest. Since 1978, China has implemented a number of ecological construction projects that have reduced desertification from 1999 to 2004 and from 2005 to 2009, and the number of dust and sand storm days from 9.3 d between 1954 and 1959 to 4.4 d between 2000 and 2007. The results could improve understanding of desertification and blown sand disasters in China and provide valuable experiences for global desertification control.

Blown sand motion within the sand-control system in the southern section of the Taklimakan Desert Highway

Although scientists have performed many studies in the Taklimakan Desert, few of them have reported the blown sand motion along the southern edge of the Taklimakan Desert Highway, which differs significantly from the northern region in terms of aeolian sand geomorphology and formation environment. Based on the field ob- servation data of airflow and aeolian sand transport, continuous monitoring data of erosional and depositional processes between 14 April 2009 and 9 April 2011 and data of surface sand grains from the classical section along the southern edge of the Taklimakan Desert Highway, this paper reported the blown sand motion within the sand-control system of the highway. The main results are as follows： 1） The existing sand-control system is highly effective in preventing and controlling desertification. Wind velocities within the sand-control system were ap- proximately 33%-100% of those for the same height above the mobile sand surface. Aeolian sand fluxes were approximately 0-31.21% of those of the mobile sand surface. Sand grains inside the system, with a mean diameter of 2.89 q）, were finer than those （2.15 q）） outside the system. In addition, wind velocities basically followed a loga- rithmic law, but the airflow along the classical section was mainly determined by topography and vegetation. 2） There were obvious erosional and depositional phenomena above the surface within the sand-control system, and these phenomena have very consistent patterns for all observation points in the two observed years. The total thicknesses of erosion and deposition ranged from 0.30 to 14.60 cm, with a mean value of 3.67 cm. In contrast, the deposition thicknesses were 1.90-22.10 cm, with a mean value of 7.59 cm, and the erosion thicknesses were 3.51-15.10 cm, with a mean value of 8.75 cm. The results will aid our understanding of blown sand within the sand-control system and provide a strong foundation for optimizing the sand-control system.

Influence of Golmud-Lhasa Section of Qinghai-Tibet Railway on Blown Sand Transport

The Qinghai-Tibet Railway(QTR) passes through 281 km of sandy land, 11.07 km of which causes serious sand damage to the railway and thus, the control of blown sand is important for the safe operation of the railway. Construction of the railway and sand prevention system greatly changed the blown sand transport of the primary surface. Effective and feasible sand-control measures include stone checkerboard barriers(SCBs), sand fences(SFs), and gravel coverings. This study simulated the embankments, SCBs and SFs of the QTR in a wind tunnel, and analyzed their respective wind profile, sand deposition, and sand-blocking rate(SBR) in conjunction with field data, aiming at studying the influence of Golmud-Lhasa section of the QTR and sand prevention system on blown sand transport. The results of wind tunnel experiments showed that wind speed increased by 67.7%–77.3% at the upwind shoulder of the embankment and decreased by 50.0%–83.3% at upwind foot of embankment. Wind speed decreased by 50.0%–100.0% after passing through the first SF, and 72.2%–100.0% after the first row of stones within the first SCB grid. In the experiment of sand deposition, the higher the wind speed, the lower the SBR of SCB and SF. From field investigation, the amount of sand blocked by the four SFs decreased exponentially and its SBR was about 50.0%. By contrast, SCB could only block lower amounts of sand, but had a higher SBR(96.7%) than SF. Although, results show that SFs and SCBs along the Golmud-Lhasa section of the QTR provide an obvious sand blocking effect, they lead to the deposition of a large amount of sand, which forms artificial dunes and becomes a new source of sand damage.

Study on the optimization of the combined blown converter process in Chongqing Iron and Steel Company

The effects of lance height and bottom blown flowrate on the mixed time, the splashing amount, the penetrating depth, and the level fluctuation of an 85 t combined blown converter have been studied using a water model. The results show that the maximal stirring energy is provided to the bath at the top lance height of about 50-100 mm. When the top lance height is in the range ofg0- 110 mm, the splashing amount caused by the top jet can reach the maximal value. The appropriate operational parameters of Chongqing Iron and Steel Company （CISC） converter have been established that the top lance height is 1600-1760 mm and the bottom blowing flowrate is 240-480 Nm^3/h in the primary phase of a heat, 1100-1300 mm and 160-200 Nm^3/h in the second phase, and 1040-1120 mm and 200-350 Nm^3/h in the end phase. Also, the trial shows that the metallurgical result of the studied blow pattern is better than that of the former pattern. At the starting 3-4 min of a heat, the strong splashing is eliminated. 2008 University of Science and Technology Beijing. All rights reserved.

Experimental analysis of sand particles' lift-off and incident velocities in wind-blown sand flux

The probability distributions of sand particles＇ lift-off and incident velocities in a wind-blown sand flux play very important roles in the simulation of the wind-blown sand movement. In this paper, the vertical and the horizontal speeds of sand particles located at 1.0 mm above a sand-bed in a wind-blown sand flux are observed with the aid of Phase Doppler Anemometry （PDA） in a wind tunnel. Based on the experimental data, the probability distributions of not only the vertical lift-off speed but also the lift-off velocity as well as its horizontal component and the incident velocity as well as its vertical and horizontal components can be obtained by the equal distance histogram method. It is found, according to the results of the X^2-test for these probability distributions, that the probability density functions （pdf＇s） of the sand particles＇ lift-off and incident velocities as well as their vertical com- ponents are described by the Gamma density function with different peak values and shapes and the downwind incident and lift-off horizontal speeds, respectively, can be described by the lognormal and the Gamma density functions, These pdf＇s depend on not only the sand particle diameter but also the wind speed.

Effect of the W-beam central guardrails on wind-blown sand deposition on desert expressways in sandy regions

Many desert expressways are affected by the deposition of the wind-blown sand,which might block the movement of vehicles or cause accidents.W-beam central guardrails,which are used to improve the safety of desert expressways,are thought to influence the deposition of the wind-blown sand,but this has yet not to be studied adequately.To address this issue,we conducted a wind tunnel test to simulate and explore how the W-beam central guardrails affect the airflow,the wind-blown sand flux and the deposition of the wind-blown sand on desert expressways in sandy regions.The subgrade model is 3.5 cm high and 80.0 cm wide,with a bank slope ratio of 1:3.The W-beam central guardrails model is 3.7 cm high,which included a 1.4-cm-high W-beam and a 2.3-cm-high stand column.The wind velocity was measured by using pitot-static tubes placed at nine different heights(1,2,3,5,7,10,15,30 and 50 cm)above the floor of the chamber.The vertical distribution of the wind-blown sand flux in the wind tunnel was measured by using the sand sampler,which was sectioned into 20 intervals.In addition,we measured the wind-blown sand flux in the field at K50 of the Bachu-Shache desert expressway in the Taklimakan Desert on 11 May 2016,by using a customized 78-cm-high gradient sand sampler for the sand flux structure test.Obstruction by the subgrade leads to the formation of two weak wind zones located at the foot of the windward slope and at the leeward slope of the subgrade,and the wind velocity on the leeward side weakens significantly.The W-beam central guardrails decrease the leeward wind velocity,whereas the velocity increases through the bottom gaps and over the top of the W-beam central guardrails.The vertical distribution of the wind-blown sand flux measured by wind tunnel follows neither a power-law nor an exponential function when affected by either the subgrade or the W-beam central guardrails.At 0.0H and 0.5H(where H=3.5 cm,which is the height of the subgrade),the sand transport is less at the 3 cm height from the subgrade surface than at the 1 and 5 cm heights as a result of obstruction by the W-beam central guardrails,and the maximum sand transportation occurs at the 5 cm height affected by the subgrade surface.The average saltation height in the presence of the W-beam central guardrails is greater than the subgrade height.The field test shows that the sand deposits on the overtaking lane leeward of the W-beam central guardrails and that the thickness of the deposited sand is determined by the difference in the sand mass transported between the inlet and outlet points,which is consistent with the position of the minimum wind velocity in the wind tunnel test.The results of this study could help us to understand the hazards of the wind-blown sand onto subgrade with the W-beam central guardrails.

Dynamic Characteristics Analysis on Wind-Blown Sand Ground under Dynamic Compaction Vibration

In the 6000 kN·m energy level dynamic compaction on Inner Mongolia wind-blown sand foundation treatment process, the dynamic characteristics and dynamic response are measured. Vibration action time, vibration main frequency, peak acceleration and peak velocity are analyzed. The vibration acting time is very short, the vertical average vibration acting time increases obviously with distance increasing, and the horizontal average vibration time does hardly change. The main frequency of vibration is at 4.60 - 24.90 Hz, which depends on the soil properties and soil layer distribution. The peak acceleration and peak velocity space distribution are similar. The maximum of horizontal acceleration peak is close to vertical velocity peak, and is near to 51 g under rammer. The maximum of horizontal velocity peak is close to vertical velocity peak, and is near to 54 m/s under rammer. The peak acceleration and velocity are rapidly attenuated, but the vertical peak acceleration and peak velocity are slowly attenuated than horizontal direction. The effective treating depth arrives 13 m for wind-blown wind, peak acceleration is 1.8 g or so, and peak velocity is 2.1 m/s or so. Horizontal treating range is 2.6 times of rammer diameter, and vertical treating range is 5.65 times of rammer diameter.

Ultravilolet-radiation-induced graft polymerization of acrylamide onto the melt-blown polypropylene filter element by dynamic method

By dynamic method under UV irradiation, commercial melt-blown polypropylene （PPMB） filter element was modified with acrylamide （AAm） using benzophenone （BP） as initiator. Attenuated total reflection-Fourier transform infrared spectroscopy and scanning electron microscope verified that polyacrylamide chain was grafted on the fiber surface of PPMB filter element. Elemental content analysis with energy dispersive X-ray of fibers revealed that the polymerization content in the inner part of filter element was relatively higher than that in the outer. Degree of grafting changed with initiator concentration, monomer concentration, reaction temperature and reached 2.6% at the reaction condition： CBp=0.06 mol/L, CAAm=2.0 mol/L, irradiation time： 80 min, temperature： 60℃. Relative water flux altered with the hydrophilicity and pore size of filter element. In the antifouling test, the modified filter gave greater flux recovery （approximately 70%） after filtration of the water extract of Liuweidihuang, suggesting that the fouling layer was more easily reversible due to the hydrophilic nature of the modified filter.

Prevention and management of wind-blown sand damage along Qinghai-Tibet Railway in Cuonahu Lake area

This paper analyzes the characteristics of climate, geology and geomorphology, vegetation, and sand dune distribution in the Cuonahu Lake area beside the Qinghai-Tibet Railway. The types and causes of railway blown-sand hazards are discussed, and the effectiveness of various sand-controlling measures is assessed. From the perspective of integrated management, a sand-controlling system that combines several engineering measures, including nylon net sand barriers, concrete sand barriers, movable-board sand barriers, sand interception ditches, gravel/rock cover, film sandbags, and permanent vegetation is most beneficial.

Measurement of radial temperature distributions of the blown CO2 arcs under different conditions

In this paper, the radial temperature distributions of the blown CO2 arcs in a model gas circuit breaker were investigated by optical emission spectroscopy methods. The CO2 flows with different flow rates(50, 100 and 150 1 min^-1) were created to axially blow the arcs burning in a polymethyl methacrylate(PMMA) nozzle. Discharges with different arc currents(200 and 400A) were conducted in the experiment. The absolute intensity method was applied for a carbon ionic line of 657.8 nm to obtain the radial temperature profiles of the arc columns at a cross-section 1 mm above the nozzle. The calibration for the intensity of the CⅡ 657.8 nm line was achieved by the Fowler–Milne method with the help of an oxygen atomic line of 777.2 nm.The highest temperature obtained in the arc center was up to 19 900 K when the arc current was 400 A and the CO2 flow rate was 50 1 min^-1, while the lowest temperature in the arc center was about 15 900 K when the arc current was 200 A and the CO2 flow rate was 150 1min^-1. The results indicate that as the arc current increases, the temperature in the arc center would also increase apparently, and a larger gas flow rate would lead to a lower central temperature in general. It can also be found that the influence of the CO2 flow rate on the arc temperature was much less than that of the arc current under the present experimental conditions. In addition,higher temperature in the arc center would cause a sharper temperature decrease from the central region towards the edge.

NUMERICAL SIMULATION ON FLOW AND MIXING PROCESSES IN BOTTOM BLOWN LADLES

An improvement on the flow and mixing conditions in bottom blown ladles may be made by either shifting the nozzle from centre to off-centre or changing from one to two nozzles. Thus the shorter time for homogeneous mixing in ladle seems to be available.

Simulation of Melt Blown Web and the Effect of Its Pore Size Distribution on Filtration Performance

In this paper melt blown webs with different fiber dis-tributing density were simulated by the computer,and then their pore size distribution was calculated with the image analysis.Based on simulated fiber webs,the effect of 10% big pores on the filtration properties was ana-lyzed theoretically.It is found that the pore radius be-comes smaller and its distribution becomes more uniformwith increasing line density,i.e.,the fiber distributing density.The flow proportion in these 10% big pores is linearly increased with increasing the standard

Relationships between the Processing Parameters of Melt Blown Nonwoven Fabric and Its Structure and Filtration Property

Based on the processing experiment and sodium flame test this paper deals with the relationship between processing parameters, structure, and filtration property of melt blown fabric. Through the image analysis of Questar micro-images in combination with the SEM observation and the measurement of some macrostructure indices, the relationship between the processing parameters and the structure especially the microstructure is emphasized Finally the effect of somestructure factors on filtration properties is discussed theoretically.

The Effects of Applying Organic Matter in Wind Blown Soil on Microbial Biomass and Enzyme Activity

Field experiment was conducted to study the effect of applying organic matter in wind blown soil on microbial biomass and enzyme activity.The results showed that microbial biomass and enzyme activity keep dynamic changes during wheat growing season in wind blown soil,and reached the peak level in wheat booting stage.Compared with chemical fertilizer,all the other treatments could increase the microbial biomass in different degree,the same as catalsae and alkaline phosphatase activity,But urease activity was slightly difference from them.

Electromagnetic scattering of charged particles in a strong wind-blown sand electric field

Some field experimental results have shown that the moving sands or dust aerosols in nature are usually electrified,and those charged particles also produce a strong electric field in air, which is named as wind-blown sand electric field.Some scholars have pointed out that the net charge on the particle significantly enhances its electromagnetic(EM) extinction properties, but up to now, there is no conclusive research on the effect of the environmental electric field. Based on the extended Mie theory, the effect of the electric field in a sandstorm on the EM attenuation properties of the charged larger dust particle is studied. The numerical results indicate that the environmental electric field also has a great influence on the particle's optical properties, and the stronger the electric field, the bigger the effect. In addition, the charged angle, the charge density, and the particle radius all have a specific impact on the charged particle's optical properties.

PANDERIVATIVE BLOWN-UP OF GROUND TEMPERATUREAND PREDICTING EARTHQUAKE

According to the blown-up theory (described in references [1,2]) for nonlinear dynamic system on the relationship of general pansystem transformation, optimisation and panderivative blown-up, by means of blown-up theory, we demonstrate that the blown-up of nonlinear heat conductive equation is similar to the evolution of observational ground temperature 'flow' in this paper. And a successful simulation of Tang Shan Earthquake in 1976 has been given. The result of simulation indicates that the blown-up of ground temperature 'flow' around earthquake can be applied to predict earthquake. As for Tang Shan Earthquake, the predicting time is about five months. If ground temperature 'flow' that embodies the earth's crust satisfies the unintegral panderivative equation, we can demonstrate its mechanism and forecast earthquake with enough information.

MELT-BLOWN NONWOVEN FOR AIR FILTRATION

The technical parameters and the structural factors of melt-blown nonwovens used as filteringmedium are analysed,the orientation of particles filtered in a filter is described,and the optimalparameters for air filtration are obtained.The results are shown as follows:the ratio of tenacity oflongitudinal to cross direction has a close agreement with the random coefficient of fiber arrange-ment in practice;large particles are most likely trapped on the surface of a filter,and smaller parti-cles are filtered throughout the depth of a filter,and the deeper,the smaller;moreover,higher fil-tering efficiency and lower pressure drop can be effected through the optimization of parameters.

Probability of rebound and eject of sand particles in wind-blown sand movement

When incident particles impact into a sand bed in wind-blown sand movement, rebound of the incident particles and eject of the sand particles by the incident particles affect directly the development of wind sand flux. In order to obtain rebound and eject lift-off probability of the sand particles, we apply the particle-bed stochastic collision model presented in our pervious works to derive analytic solutions of velocities of the incident and impacted particles in the postcollision bed. In order to describe randomness inherent in the real particle-bed collision, we take the incident angle, the impact position and the direction of resultant action of sand particles in sand bed on the impacted sand particle as ran- dom variables, and calculate the rebound and eject velocities, angles and coefficients （ratio of rebound and eject velocity to incident velocity）. Numerical results are found in accordance with current experimental results. The rebound and eject liftoff probabilities versus the incident and creeping velocities are predicted.

Sinopec Yizheng Chemical Fiber Co.,Ltd.accelerates the construction of 8 meltblown nonwovens production lines

On March 2,the feasibility report of Sinopec Yizheng Chemical Fiber 4,000t Polypropylene Meltblown Nonwovens Project was formally completed.The project is expected to be completed in mid-April.By then,the daily output of meltblown nonwovens can reach 12 tons,which can be used to process 12 million medical flat masks.

Mathematical model of pyritic smelting process for copper-nickel mineral in oxygen top-blown furnace

Mathematical model for mass transfer of chemical reactions on the surface of the smelting bath pit in oxygen top blown smelting furnace was put forward. Additionally, one of two mathematical models for mass transfer of chemical reactions forming copper matte in smelting bath and the other for parameters of smelting process were developed. The verification tests were simultaneously carried out in a pilot scale furnace and the experimental results show that these mathematical models are convincing. Thus, these numerical models are reliable to simulate pyritic smelting process for copper nickel mineral in oxygen top blown furnace.