Abstract:To investigate different effects of anaerobic modes on recovery of partial nitrification (PN), two-stage continuous stirred-tank reactors (CSTR)1# and 2# were used at room temperature (20±2) ℃. The experiment had three stages (S1, S2 and S3). During S1, 1# was maintained anaerobic / anaerobic (DO: 0-0. 1, 0-0. 1 mg / L), 2# was maintained anaerobic / oxic (DO: 0-0. 1, 0. 6-0. 8 mg / L). During S2, 1# was maintained oxic / oxic (DO: 0. 2-0. 4, 0. 6-0. 8 mg / L), 2# was continually maintained anaerobic / oxic (DO: 0-0. 1, 0. 6-0. 8 mg / L). To investigate stability of PN after recovery, S3 was carried out. During S3, 1# and 2# was maintained oxic / oxic (DO: 1. 0-1. 2, 1. 0-1. 2 mg / L) The following paremeters (time of recovery of PN and stability of PN) were investigated. It demonstrated that the recovery time of 1# was shorter than that of 2# by 12 d. However, PN in 2# was more stable when DO increased to 1. 0-1. 2 mg / L. Efficient PN could be recovered by the mode of first anaerobic / anaerobic (DO: 0-0. 1, 0-0. 1 mg / L) then oxic / oxic (DO: 0. 2-0. 4, 0. 6-0. 8 mg / L). Afterwards, stable PN could be maintained by anaerobic / oxic (DO: 0-0. 1, 0. 6-0. 8 mg / L).

Abstract:Content of EPS affects not only the formation and stability of anammox granular sludge, but also the performance of reactor. To study the effect of influent water quality on the EPS content, sixteen SBR reactors with different total nitrogen concentrations, different IC/TN ratios and different COD/TN were operated and compared. Experimental results indicated that the content of EPS increased during the substrate utilization phase, but declined under the shortage phase. Specifically, the EPS content increased slighty with the increasing of total nitrogen concentration from 35 to 280 mg/L, however, it decreased significantly once the total nitrogen concentration exceeded 280 mg/L. With a IC/TN of 0.01-0.2, the content of EPS increased with a continuous input of inorganic carbon, but the inorganic carbon concentration had no significant effect on EPS content when IC/TN>0.2. Under the condition of COD/TN < 0.5, higher organic matter promoted EPS formation, but it inhibited EPS formation when COD/TN>0.5. Thus, long substrate utilization phase and the shortage phase should be avoided during the operation of anammox reactor, and the total nitrogen concentration should be maintained between 150-210 mg/L, IC/TN should be 0.1-0.2, COD /TN should be lower than 0.5.

Abstract:To examine the effects of different coagulants on membrane fouling in the coagulation/aid-coagulation/ultrafiltration process for high turbidity surface water purification, Malvern laser particle size analyzer and micro-scale ultrafiltration unit were used to investigate membrane fouling caused by the flocs formed by coagulants (i.e. aluminium polychlorid (PACl), ferric trichloride (FeCl₃)) and aid-coagulant (polyacrylamide (PAM)). The results indicated that, with the constant dosage of combined coagulants (PACl=FeCl₃=3 mg/L), the PAM dosage of 0-0.4 mg/L rendered the d50 of flocs exhibited an obvious increase (eventually reached to 1 000 μm) compared to those with single coagulant dosage of PACl (3-370 μm) or FeCl₃(360-420 μm). With the dosage of PAM increased, specific membrane flux increased (PACl:0.56-0.64; FeCl₃: 0.71-0.76) and cake resistance decreased (PACl:0.90×10^-11-0.52×10^-11 m^-1; FeCl₃:0.47×10^-11-0.28×10^-11 m^-1). However, when the dosage of PAM increased to 1.0 mg/L, the membrane flux decreased significantly to 0.48 while cake resistance increased to 1.55×10^-11 m^-1. An optimum flocculant dosage (0.4 mg/L) that caused the minimum membrane fouling was confirmed. Furthermore, the results obtained from Nanoseries Zetasizer and scanning electron microscopy (SEM) demonstrated that cake layer was the dominant fouling mechanism under different conditions and membrane pore blocking was severe with higher PAM dosage.

Abstract:The aim of this work is to investigate the practical effect of the combined advanced oxidation processes (catalytic ozonation UV/ H₂O₂ biological activated carbon (BAC)) on improving the water quality of micro polluted raw water from Huaihe river. The results suggest that catalytic ozonation combined with BAC process could improve the water quality by enhancing the removal efficiency of UV₂₅₄, DOC, ammonia nitrogen, COD_Mn and trihalomethanes formation potential (THMsFP), while it did not bring any bromate risk because of low bromate formation after catalytic ozonation. The average removal rates of UV₂₅₄, DOC and COD_Mn by catalytic ozonation were 21.8%, 8.1% and 10.8%, respectively. And the BAC filter could efficiently remove the ammonia nitrogen in water with a highest removal rate of 61%. The average reduction percentages of DOC and COD_Mn by BAC process were 10.4% and 15.3%, respectively. Furthermore, the catalytic ozonation process could significantly decrease THMsFP, with an average removal rate of 34.9%, and the maximum rate could arrive to a percentage of 53.2% during the test. However, UV/H₂O₂ process in this project could not furthered improve the water quality of the Huaihe river with seasonal characteristics of low temperature and low turbidity. Therefore, the combination of catalytic ozonation UV/H₂O₂ is of little significance, but catalytic ozonation BAC sand filter process is a necessary combination mode of advanced oxidation process to ensure the safety and reliability of drinking water in the practical production design. Considering the decomposition role of UV for residual ozone, catalytic ozonation UV BAC sand filter process are the recommended processes as AOPs for micro polluted river water. The results from the demonstration project can provide a reference for improving the quality of effluent water with low temperature and turbidity and reconstruction for the drinking water treatment plant.

Abstract:The aim of this work is to investigate the transformation efficiency of triclosan (TCS) at the wavelength of 254 nm in the presence of H₂O₂. The effects of oxidant dosage, TCS concentration, NOM, and pH were evaluated. Most of these kinetic results could be described by a steady-state kinetic model. Increasing dosage of H₂O₂ increased the observed pseudo-first-order rate constant for TCS degradation (k_obs) when H₂O₂ < 1 mmol/L. However, when H₂O₂ >1 mmol/L, k_obs decreased with H₂O₂ dosage increased due to the effects of radical scavenging by H₂O₂. Increasing concentration of TCS decreased the steady-state concentration of HO ·. The presence of NOM significantly decreased k_obs due to the effects of UV absorption and radical scavenging. When pH=9, k_obs was higher than that when pH=5-7. This could be attributed that the deprotonated TCS was more reactive than protonated TCS. Six products were detected in TCS treated by UV/H₂O₂. A tentative pathway was proposed, where dechlorination and hydroxylation reaction were involved.

Abstract:To study the effects of worm predation on membrane fouling in an MBR+worm reactor, an MBR+worm reactor with worm (R1) and an MBR+worm reactor without worm (R2) were operated in parallel. Variation of transmembrane pressure (p_TM) and microbial metabolites were studied in the MBR (S-MBR) of the R1 and the MBR (C-MBR) of the R2. Denatured gradient gel electrophoresis (DGGE) was used for analyzing the composition and distribution of microbial community in the S-MBR and the C-MBR. The results showed that the membrane fouling cycles of the S-MBR and the C-MBR were 90 d and 28-37 d, respectively. Worm predation decreased the polysaccharide and proteins in the soluble microbial products (SMP) and extracellular polymeric substances (EPS) of the S-MBR. Alphaproteobacterium, Betaproteobacterium, Deltaproteobacterium, Geobacter on the membrane wire surface of the S-MBR and Azorhizobium, Rhodobacter, Gammaproteobacterium, Flavobacteria on the membrane wire surface of the C-MBR played an important role in the membrane fouling. Caldilinea was suggested to be related to the membrane fouling alleviation of the S-MBR. Worm predation changed the microbial community structure of the S-MBR, resulting in membrane fouling alleviation.

Abstract:Atrazine residue in water poses a serious threat to the environment and human health. Phytoremediation stood out as a potential technology for in-situ remediation of atrazine in the environment. A pot culture experiment was conducted to investigate the effects of arbuscular mycorrhizal fungi (AMF) on the phytoremediation of atrazine by Canna indica L. var. flava Roxb. The results demonstrated that arbuscular mycorrhizal fungi formed a stable symbiosis with canna a month after its inoculation, and the root colonization rate was (22.1±4.6)%. Arbuscular mycorrhizal fungi relieved the inhibition effect of atrazine on canna growth, and improved the plant height, root length and biomass of canna under the stress of atrazine; mycorrhizal dependency on the growth of canna was significant, and achieved the maximum value at 5 mg·L^-1 concentration of atrazine. Inoculation of arbuscular mycorrhizal fungi significantly increased the canna phytoremediation degradation rate of atrazine, and reduced the half-life of atrazine; furthermore, inoculation of arbuscular mycorrhizal fungi improved the atrazine concentration range of canna phytoremediation. This study shows that canna inoculated with arbuscular mycorrhizal fungi is an ideal choice of atrazine pollution remediation, and may ultimately serve as a viable phytoremediation solution for in situ remediation of atrazine in water.

Abstract:Subsurface drainage system is an efficient system to drain extra flood out from the farmland. But this system also changed the transport pathway and speed of water and the dissolved pollution in farmland. To get a full understanding of vertical transportation of nitrate and phosphate in subsurface drainage agricultural watershed, finite element analysis technology was used to make the numerical simulation of mass transfer of soil column. Results show that there is no water and dissolved pollutant in pipe after 5 h rainfall with intensity of 4 mm/h, because the rainfall in 5 h is not enough to saturate the soil layer from surface to pipe. But if extending the rainfall duration to 10 h, the soil became saturated and then the nitrate and phosphate loss observed. The nitrate loss was extremely higher than phosphate (nitrate concentration is 9-10 mg/L, phosphate is 0.05-0.1 mg/L). After 24 h rainfall event, the nitrate loss reached to the maximum. The nitrate loss in tile water intensity was at an exponential growth but phosphate just increased at a liner growth. This phenomenon may be caused by the differences of material properties.

Abstract:The whole water is assigned to each node according to the pipes' length in micro-dynamic hydraulic model of water supply network. Traditional hydraulic model of water supply network ignored the category of nodes flow and distributed the total leakage to the network equally. To solve this problem, nodes flow of traditional hydraulic model were divided into water users' consumption and water leakage, and the improved consistent leakage model distributed the leakage flow based on length and built the relationship between the leakage and pressure, then the pressure-driven nodes hydraulic mode (PDD) was finally established. The model was checked based on actual measuring point data, and reached the model checking standard. Based on the actual network data in Y city, the average leakage rate is calculated as well as the fitness function between water supply and actual water supply, then the leakage coefficient of the network model is achieved, and finally the leakage simulation based on pressure-driven nodes flow of the water supply is established. The results show that, the checked PDD model is in good agreement with the actual operation pressure of water supply network so that it can detect and evaluate the leakage control.

Abstract:The morphology of fibrous adsorbents possessed the large degree of freedom so that they can be used flexibly and recycled easily in emergency water treatment. Traditionally, long time preparation of the fibrous adsorbents severly limited their wide application. To solve the above mentioned problem, the microwave-assisted method was applied to prepare a new adsorbent which was derived from the low-cost and available jute. The pretreatment process was optimized with the response surface methodology (RSM) method based on single factor experiments, and the performance of microwave-assisted method was compared with the control test by alkali boiling under water-bath heating. The above pretreated jute was then grafted with carboxyl groups, and the contribution of microwave during graft reaction was clarified. Finally, the adsorption behaviors of modified jute toward heavy metal ions removal were studied. Compared to alkali boiling under water-bath heating, the pretreatment time was reduced 70% and alkaline mass fraction was declined from 20% to 16% under microwave-assisted method. Initial microwave-assisted grafting reaction rate was about 18.6 times higher than that under water-bath heating, because the microwave heightened the pre-exponential factor and lowered the apparent activation energy of graft reaction. Modified jute exhibited a higher removal efficiency of heavy metal ions than raw jute.

Abstract:In order to reduce the impact of heavy metals on the biological treatment system of electroplating wastewater, a lab-scale process combined with hydrolysis reactor and membrane bioreactor (MBR) was used to treat electroplating wastewater. Taking Cu²⁺ and Ni²⁺ as research objects, the effects of different metal concentrations on the electroplating wastewater treatment were studied, and the changes of DOMs and microbial activity in water were analysed simultaneously. The experimental results showed that the removal efficiencies of COD and NH₄⁺-N were above 75% and 45%, respectively, when the concentration of Ni²⁺and Cu²⁺ was 5-20 mg/L. Nitrification bacteria's ability to resist heavy metal impact was weak. The tolerance concentration of Ni²⁺ in hydrolysis reactor combined with MBR was 20 mg/L and only 10 mg/L in MBR. The hydrolysis reactor could convert most of HPI into HPO-A, which could improve the biodegradability of refractory organic compounds, and the content of aromatic compounds was obviously decreased. With the increase of Ni²⁺ and Cu²⁺, the SOUR value of activated sludge in MBR reactor was gradually decreased, but the inhibition rate of SOUR in hydrolysis reactor combined with MBR was 5% lower than that in MBR. Due to the hydrolysis, the toxicity of heavy metals decreased. In hydrolysis reactor combined with MBR, the activity of microorganism was higher, and the content of EPS and the effluent concentration were significantly lower than those in MBR. The formation of colloid, dissolved organic matter and sludge cake layer could be reduced effectively, which retarded the rate of membrane fouling.

Abstract:The biological stability is closely associated with the safety of drinking water and can be controlled effectively by prohibiting bacterial regrowth. The effects of three main nutrients (organic carbon, phosphorus, nitrogen) and chlorine on bacterial regrowth in drinking water were investigated using BRP method in lab-scale experiments. The critical values of carbon, nitrogen and phosphorus promoting bacterial growth were 250, 7 and 3 μg/L respectively, while the yield values for heterotrophic bacteria of the three nutrients were 2.35×10⁶(R²=0.99, p < 0.05), 9.76×10⁷ (R²=0.91, p < 0.05) and 1.76×10⁸ CFU/μg (R²=0.91, p < 0.05) during the absence of only one kind of nutrient. When two kinds of nutrients were in deficiency, nutrient which was relatively low would be the main BRP limiting factor and decrease the supporting ability of the other nutrients on bacterial regrowth. Moreover, BRP decrease with the increasing amount of free chlorine in drinking water. When the concentration of free chlorine reached 0.5 mg/L, the growth of bacteria was inhibited obviously. In other words, free chlorine weakened the ability of nutrients supporting bacterial regrowth.

Abstract:Biochars converted from pyrolysis of walnut shell and coconut shell were used as an alternative adsorbent for adsorbing volatile organic compounds (VOCs). Biochars were characterized by Elemental analysis, Fourier transform infrared spectra, Boehm titration and specific surface area and porosity analyzer. And the adsorption behaviors of benzene and toluene on biochar were investigated by column experiments. The results suggested that the adsorption performance of coconut shell biochar was better than walnut shell biochar under the same preparation conditions. The adsorption capacity of biochar was increased with the increasing pyrolytic temperature within the temperature range (400 ℃ to 700 ℃). The adsorption process of low pyrolytic temperature biochar (400 ℃) and high pyrolytic temperature biochar (700 ℃) were described with the pseudo-second-order model and the pseudo-first-order model, respectively. At the adsorption temperature of 30 ℃, the isothermal adsorption process could be fitted by Toth model, and the maximal adsorption amounts of benzene and toluene calculated by Toth were 18.98 and 61.73 mg/g. The surface acidic groups and porous structure of biochar played an important role on adsorption capacity, affecting the surface adsorption and intraparticle diffusion process.

Abstract:In order to solve the biologically pretreated coal gasification wastewater (CGW) still contained a large number of toxic and refractory compounds, posing great hazard to the environment, sludge based activated carbon was prepared from the sewage sludge produced during gasification wastewater (CGW) treatment via the loading process of manganese and ferric oxides (main Mn₃O₄ and Fe₃O₄, loading dose of 15.52% and 7.45%, respectively), and the zone catalysts exhibited a specific surface area of 327.5 and 339.1 m² / g.Pilot-scale tests demonstrated that the additive of the prepared catalysts significantly improved the removal efficiency of pollutants during ozonation treatment, with an effluent COD, TOC, total phenols and NH₄⁺ -N concentrations of 41-43, 19-20, 0.6-0.9 and 4.3-4.5 mg / L, respectively, can meet class-I criteria of the Integrated Wastewater Discharge Standard.Moreover, utilization rate of ozone with catalysts additive (1.24 mg / mg) increased 40% as compared with the test only with ozone additive, would significantly save the operation cost.In comparison with the fresh catalysts, COD removal efficiency only decreased by 5.2% after 50th successive catalytic ozonation.The cost of catalysts production was about 5 000 RMB / t average.Overall, efficient, stable, economical and sustainable characteristics of the prepared catalysts made it suitable for advanced treatment of CGW.

Abstract:At the regulatory detailed planning stage, the regulatory planning parameters which influenced thermal environment were classified and the new standard effective temperature, wet bulb globe temperature, urban heat island intensity were all considered as the thermal environmental evaluation index. Based on the developed urban regional thermal climatic prediction model, one-variable method was adopted to analyze the effects of different regulatory planning parameters on these evaluation index. The hourly simplified models of each evaluation index were obtained and showed rapid, simple, and accurate characteristics by comparing with the original model. By combining the data input module, the meteorological parameter maintenance module, the regulatory planning parameter maintenance module, graph presentation module, data output module and the hourly simplified calculation models of evaluation index, the thermal environmental evaluation software for urban detailed regulatory plan was developed and then applied to a field study in Guangzhou. Hourly thermal environmental indicators OUT-SET^*, UHII, and WBGT of four test blocks were obtained and the spatial visualizations were realized. Results showed that the average OUT-SET^* within the whole research regions ranged from 28 ℃ to 30.5 ℃, and the maximum WBGT varied between 29 ℃ and 30 ℃. The UHII of block 1 to 3 varied between 0.4 ℃ and 1.2 ℃ while that of block 4 had the urban cool island effects. Thus, it reveals that different regulatory detailed planning indicators have important impacts on the thermal environmental parameters.

Abstract:Coil-wound heat exchangers are the core equipment for liquefaction of natural gas, however, the experimental research on large-scale coil-wound liquefied natural gas (LNG) heat exchangers is relatively weak and the design theory is also imperfect in China. In order to obtain the characters of flow and heat transfer at the tube side of coil-wound LNG heat exchangers, a new experimental method which can simulate the actual coil-wound LNG heat exchangers operation conditions was presented, and then the corresponding test-rig was designed, developed and debugged. For guaranteeing the accuracy of the experimental data, the test-rig was verified by using liquid propane as experiment medium. The tested heat transfer coefficients of propane under different experimental conditions were compared with those from the classic tube heat transfer correlations in the same experimental conditions. It is concluded that the experimental conditions can meet the actual coil-wound LNG heat exchangers operation conditions, and the test-rig can operate stably. The deviation between the tested values and the predicted values is less than±10%. So the accuracy of the test-rig is high and the experimental data are credible. The test-rig provides an experimental basis for comprehensive research on flow and heat transfer under the actual conditions for large-scale coil-wound heat exchangers.

Abstract:To use LNG cold energy in cold storage system effectively, a new cold storage system using LNG cold energy was designed from the perspective of cascade utilization of LNG cold energy, which achieved cascade utilization of LNG cold energy in the LNG exchanger and the cold storage terminal. In addition, the thermodynamics and economy performance of the system were simulated and analyzed by HYSYS, respectively. Results indicated that COP of the cold storage system was 1.82 and the exergy efficiency was 80.2%. Besides, the exergy loss of LNG exchanger was the largest, which constituted 79.8% of the total exergy loss in the system, and it decreased with the LNG inlet temperature rising. Moreover, as the LNG inlet temperature and gasification pressure increased, both COP and exergy efficiency of the cold storage system rose. The system had good economic benefits, with the payback period of 4.77 years. It was quite obvious that LNG cold energy was a new cold energy source for cold storage system and adding cold-storage equipment and pressure pump in LNG inlet terminal could improve COP and exergy efficiency.

Abstract:Aiming at the problem of serious deviation from the actual energy consumption for the calculated energy consumption with the continuous operation mode prescribed in current design standard for residential building energy efficiency in hot summer and cold winter zone, a questionnaire survey for the use mode of air conditioner has been conducted in Hangzhou, a typical city in this climate zone. It was found that there widely exists intermittent energy consuming method in the residential buildings of this area. The air conditioning using behavior was affected by thermal feeling of human body. The greater the indoor air temperature deviates from the the human body comfort scope, the higher the air conditioning opening rate is. DeST was employed to calculate the annual energy consumption of the residential building with internal and external wall insulations under different occupant behaviors, and then the annual energy saving effects were analyzed. The results show that in continuous energy consuming method, the annual energy saving effect for external insulation is better than that for internal insulation; in intermittent energy consuming method without considering tolerate temperature, the annual energy saving effect for internal insulation is better than that for external insulation. Under the condition of variable tolerate temperature, the critical tolerate temperature point for internal and external insulation with the same energy saving effect is 31.8 ℃ in summer and 13.4 ℃ in winter. When tolerate temperature is lower than the critical point, the internal insulation has better energy saving effect; when tolerate temperature is higher than the critical point, the external insulation has better energy saving effect. The choice of reasonable insulation means in this region was greatly affected by the air-conditioning behaviors and occupants' thermal tolerance. The critical tolerate temperature for the same energy saving of the internal and external insulations is 31.8 ℃ in summer and 13.4 ℃ in winter. Therefore, setting reasonable air-conditioning behavior in the design standard for energy efficiency is an important premise for accurately evaluating the energy saving effect of exterior wall insulation measures.

Abstract:Nowadays phase change materials (PCMs) have been used in preliminary practical engineering. However, the selection of the thermal design parameter of PCMs is really difficult on account of the change of specific heat capacity, thermal conductivity in phase change region and the impact of the latent heat. Thermal conductivity can't be used in the selection of PCMs. To provide guidance in thermal design of the wall, relative thermal conductivity (RTC) of the PCM layer was defined and its computing method was given. RTC is a thermal-physical parameter that can represent the same heat transfer capacity of PCMs with that of normal materials in the same conditions. Based on the computing method, RTC of the PCM layer in different areas were calculated, and heat transfer characteristics of PCM layers in the whole year were shown. In addition, PCM layers' utilization effects in different areas of China were analyzed. By comparing different PCM layers' RTC, it was obtained that different layers had different utilization effects. RTC can be used to select the proper PCM used in a certain area.

Abstract:Impact model between boulder and pier was built based on the Hertz contact theory and structural mechanics. Three main influence factors of impact force, including the material properties, relative size, and structure displacement were quantized and the modified formula was presented to calculate impact force. It shows that, material correction coefficient ranges from 0.20 to 0.45, which is proportional to material yield strength Y while correlated reciprocally with the equivalent modulus of system, E. The correction coefficient of ball diameter ratio exhibits that, along with the increase of structure size, it increases stably after rapid growth. Structure displacement correction coefficient is affected by the constraint condition of pier top and impact location. The practical application of this modifier formula in Dengjigou engineering result is only 6.7% of the calculated value by Hertz elastic collision theory, and according to the outcome that, relation curve between impact force and impact velocity is relatively flat, which performs in accordance with practical estimation.

Abstract:The load bearing capacity of steel structures after fire reduces mainly due to the deterioration of its mechanical properties. This paper presented an experimental study on material properties of high strength steels S460 and S690 after fire. The post-fire elastic modulus, yield and ultimate strengths, ductility and stress-strain curves were obtained and compared with the post-fire mechanical properties of mild strength steels. It is found that when the fire temperature from which the high strength steel is cooled down is less than or equal to 600 ℃, S460 and S690 can regain their original mechanical properties. When the fire temperature is up 1 000 ℃, S460 can also regain more than 75% of its original mechanical properties, but S690 only regains 64.5% of its original elastic modulus, 38.1% of its original yield strength and 57.3% of its original ultimate strength. The mechanical properties of high strength steels are different from mild strength steels. Predictive equations were proposed to evaluate the post-fire material properties of S460 and S690. Comparing with the test results, the predictive equations were validated. The predictive equations can be employed for practical inspection and appraisal of steel structures after fire with members made of S460 and S690, and provide a reference for the revision of current worldwide leading design standards.

Abstract:To study the effects of the elastic deformation of flexible paraboloid antenna on the approximate phase center in the stage of attitude adjustments, the mathematical model for solution paraboloid antenna dynamic geometric focus was established and its dynamic response characteristics were solved numerically. The FE model composed of the central platform, solar panels and paraboloid antenna was established and the natural frequencies and mode shapes of the antenna in unconstrained state were calculated. Then through co-simulation of FEM and ADAMS the zero-order rigid-flexible coupling dynamic model of the spacecraft was established, and the dynamic response of the antenna geometric focus in the process of attitude adjustments were obtained. Results show that the flexible attachments elastic vibration accompanves with rigid motions in the procedure of attitude adjustments, and the geometrical focus shock in the equilibrium position reduces spaceborne antenna pointing accuracy to some extent.

Abstract:To solve the problem that the couplant can't be used on the surface of SRM shell bonding structure in ultrasonic detection, a dry-coupled ultrasonic detection system is built, and then special-structure piezoelectric vibrator and transmission rod are designed for dry-coupled probes. Based on the time reversal, a dry-coupled ultrasonic imaging method is proposed and the time reversal principle is analyzed. The transient fluctuation chart on the focus moment is established by extracting damage scatter signals, time reversal and secondary loading. Finally, the defect images are obtained by two methods, including the sum and the product of the amplitudes of signal elements. The experiment shows that the proposed method is valid to detect the shape and the position of the defect in bonding structure.

Abstract:In order to improve the spray dust efficiency of a gas-water nozzle in the coal mine workplaces with high concentration of dust, the gas-water nozzle atomization characteristic parameters were studied through experiments, and the changing rule between the droplet average diameter and the gas/water flow was obtained; this paper studied the dust removal process of the gas-water spraying in the comprehensive tunneling face. The corresponding mathematical model was established and the expression of the gas-water nozzle's efficiency was provided. The curve of dust removal efficiency was drawn by use of Matlab. Research results show that: when the water flow remains constant, the dust removal efficiency increases with the increase of the gas flow; when the gas flow remains constant, the dust removal efficiency increases firstly and then decreases with the increase of the water flow; the larger the dust size is and the longer the effective distance of spray droplets is, the easier the dust settling is. Only when the gas flow is greater than 150×10^-5 m³/s, the dust reducing efficiency can reach 80%, and the best gas water flow ratio lies between 100 and 150. Based on the size distribution and removal requirement of dust in working face, choose the best gas/water flow can be chosen by reference to the related curve so that better dust removal effect and economic benefits can be achieved.

Abstract:In order to study the optimal delay time of inter blasthole of millisecond blasting, which is calculated through stress wave and explosive gas energy, an detonation gas motion equation and a dynamic equation are proposed, which is consisted of detonation gas destruction scope, time, and the mathematical model of velocity. Specifically, many theories, such as rock broken theory, wave theory, theory of fracture mechanics, thermodynamics theory and theory of fracture mechanics are utilized during formula derivation. Moreover, after correcting the semi-empirical formula from previous study, a theoretical model of millisecond blasting's delay time is established. As a result, the calculated optimal delay time is 25 ms after inserting the rock mechanical properties. By contrast, the experiment of delayed-detonation combination in different period, reveals that the optimal delay time is 24 ms, which is consistent with the theoretical result.

Abstract:In order to verify the insulation features and anti-freezing protection effect of all-glass evacuated tube collector, the fluid temperature in solar collector and its changing were tested experimentally in static conditions in winter night, and the heat dissipation and the average heat loss coefficient were calculated as well. The heat loss characteristics and the changing regulations were analyzed in detail. Results indicated that the lowest fluid temperature was ranged from 8 ℃ to 25 ℃, and the temperature drop rate was between 0.7 ℃/h and 1.3 ℃/h. The total amount of heat dissipation was about 1 800-4 700 kJ, and the average heat loss coefficient was 0.427 W/(m²·K) during the testing nights. The study of the heat dissipation of solar collector and the changing of the lowest fluid temperature in it, can effectively demonstrate its insulation properties, which can provide evidence for the anti-freezing of solar collector and its outdoor pipe loops in severe cold areas.

Abstract:In order to study the effect of structural connections on static performance, influence lines of three-pylon suspension bridges were analyzed. The Taizhou Yangtze highway bridge was a prototype, and its influence lines of structural response were calculated by limited displacement method, considering different cable-girder connections and pylon-girder connections. The effect of structural connections on the influence lines was also researched. The results show that, when center buckles were not assembled in three-pylon suspension bridges, the change of pylon-girder connections had an unobvious effect on the influence lines, including middle-span deflection of the girder, horizontal displacement at the top of pylons, and different value of main cable sided on the middle saddle. Also, when center buckles were assembled, the influence lines were changed remarkably, especially to amplitude in the part of local span, and to the shape in the part of adjacent span. Based on the variation of influence lines, the recommended structural connection for three-pylon suspension bridges was the rigid center buckle coupled with elastic stringer.

Abstract:To study the bearing capacity of soft soil reinforced by dynamic replacement method with various hammers, a calculation model was put forward for evaluating the soft soil's ultimate bearing capacity. A series of model tests was conducted to investigate the shape characteristics and the failure mode of the replacement piers. Based on the model test, the ultimate bearing capacity of replacement pier was established using the energy method, which was calculated using the GA_PSO optimization algorithm on the Matlab platform, and a parametric study was conducted to investigate the factors that influence the ultimate bearing capacity of the replacement pier. The test and calculation results show that the replacement pier is typically formed as a cone with cross section of an inverted trapezoid and the pier usually has a mode of bulging failure in the ultimate state. The diameter of the pier and soil strength around the pier have significant effects on the ultimate bearing capacity, which is consistent with the design concept of the dynamic replacement method with various hammer. The proposed method was verified to be feasible through comparison between calculation results and field test results.

Abstract:Biostability plays an important role in keeping drinking water quality and safety. Methods of biostability assessment are reviewed, including main indicators, traditional analytical methods and emerging ones. Merits and demerits of different analytical methods are discussed respectively. Time-consuming and inaccurate, traditional methods are acknowledged to be inadequate in the evaluation of drinking water quality. Improved methods, e.g. assimilable organic carbon (AOC), total cell concentration (TCC), adenosine tri-phosphate (ATP) methods based on flow cytometry (FCM), are accurate, simple and economical, and thus have shown tremendous potential in water monitoring and engineering practice. Emerging molecular biological methods, e.g. denaturing gradient gel electrophoresis (DGGE) and pyrosequencing, offer an insight into the changes of microbiology compositions in water treatments and distribution, and fundamentally reflect the biological stability of water quality.