Changing the balance of the MTO reaction dual-cycle mechanism: Reactions over ZSM-5 with varying contact times

The methanol to olefins （MTO） reaction was performed over ZSM‐5 zeolite at 300℃ under various methanol weight hourly space velocity （WHSV） values. During these trials, the catalytic perfor‐mance was assessed, in addition to the formation and function of organic compounds retained in the zeolite. Analysis of reaction effluents and confined organics demonstrated a dual‐cycle reaction mechanism when employing ZSM‐5. The extent of the hydrogen transfer reaction, a secondary reac‐tion in the MTO process, varied as the catalyst‐methanol contact time was changed. In addition, 12C/13C‐methanol switch experiments indicated a relationship between the dual‐cycle mechanism and the extent of the hydrogen transfer reaction. Reactions employing a low methanol WHSV in conjunction with a long contact time favored the hydrogen transfer reaction to give alkene products and promoted the generation and accumulation of retained organic species, such as aromatics and methylcyclopentadienes, which enhance the aromatic cycle. When using higher WHSV values, the reduced contact times lessened the extent of the hydrogen transfer reaction and limited the genera‐tion of methylcyclopentadienes and aromatic species. This suppressed the aromatic cycle, such that the alkene cycle became the dominant route during the MTO reaction.

Evaluation of Catalysts and Optimization of Reaction Conditions for the Dehydration of Methyl Lactate to Acrylates

The production of acrylates from biomass-originated lactic acid is of extraordinary importance, to overcome the increasing worldwide shortage of petroleum. In this study, the catalytic dehydration of methyl lactate over a calcium sulfate catalyst, with various promoters, has been carried out to identify potential catalyst/promoter combinations for acrylate production. The best catalyst for methyl acrylate formation in this study has been calcium sulfate, with cupric sulfate and phosphates as promoters. The optimal mass ratio of m（CaSOa） ： m（CuSOa） ： m（Na2HPO4） ： m（KH2PO4） is 150.0 ： 13.8 ： 2.5 ： 1.2. Effects of carrier gas, reaction temperature, feed concentration as well as contact time on the dehydration of methyl lactate have been investigated. With nitrogen as a carrier gas, a combined yield of acrylic acid and methyl acrylate is 63.9% from 60% （by mass） methyl lactate at 400℃ with 7.7 seconds contact time.

Effect of active species in crude oil on the interfacial tension behavior of alkali/synthetic surfactants/crude oil systems

The effect of active species present in crude oil on the interfacial tension （IFT） behavior of alkali/synthetic surfactants/crude oil systems was studied. The system consisted of heavy alkyl benzene sulfonate, sodium chloride, sodium hydrate and Daqing crude oil. Experimental results indicated that active species would diffuse from oil/aqueous interface to aqueous phase and finally an equilibrium could be reached in the system with increasing contact time. Moreover, the minimum IFT and equilibrium IFT values increased with increasing contact time and a linear relationship existed between dynamic IFT and f^-1/2 when IFT value approaching the minimum and after the minimum IFT was reached. This indicated that the dynamic IFT-time behavior was diffusion controlled. The oil and aqueous phases were analyzed by infrared （IR） spectroscopy. IR spectra of oil and aqueous phases illustrated that the content of active species in the oil phase decreased, but the content of active species in the aqueous phase increased after alkali reacted with crude oil. This indicated that the active species present in oil played an important role in reducing IFT.

Flow Electrification of Insulated Liquid in Metal Pipes

When relative motion occurs between a liquid and a solid, the two phases carry electric charge with opposite signs. The created charge easily accumulates in the liquid, and the amount of the charge carried in an insulated liquid refers to many factors, such as contact area with the solid surface, the contact time, and so forth. However, current theories agree that the amount of charge created during flow electrification is proportional to the contact surface. In this paper, the classical wall current theory is applied to establish an interfacial electrical double-layer model of flow electrification phenomena when an insulated liquid passes over metal pipe surface. Meanwhile, in conjunction with charge relaxation function, the relation between the charge density and flow velocity, the contact time and the contact area is obtained during the liquid flowing process. The experimental result demonstrates that the flowing charge carried in the insulated liquid is not simply proportional to the contact area, but has a non-linear dependence on the contact area and the contact time. Moreover, down flow experimental equipment pipes of different length and diameter, and dielectric hydraulic oil VG46 are used in an experimental study of laminar flow, in order to understand electrification phenomena in dielectric liquid flowing over metal pipes of different length and aperture. If they both increase linearly, charge relaxation will increase exponentially. As a result, the test result verifies related theoretical analysis, and the method given provides a theoretical basis to analyze interracial electrical phenomena.

Removal of disinfection by-products formation potential by biologically intensified process

The removal of disinfection by-products formation potential(DBPFP) in artificially intensified biological activated carbon(IBAC) process which is developed on the basis of traditional ozone granular activated carbon was evaluated. By IBAC removals of 31% and 68% for THMFP and HAAFP were obtained respectively. Under identical conditions, the removals of the same substances were 4% and 32% respectively only by the granular activated carbon(GAC) process. Compared with GAC, the high removal rates of the two formed potential substances were due to the increasing of bioactivity of the media and the synergistic capabilities of biological degradation cooperating with activated carbon adsorption of organic compounds. A clear linear correlation(R 2=0.9562 and R 2=0.9007) between DOC HAAFP removal rate and Empty Bed Contact Time(EBCT) of IBAC process was observed, while that between THMFP removal rate and EBCT of GAC was R 2=0.9782. In addition certain linear correlations between THMFP, HAAFP and UV 254 (R 2=0.855 and R 2=0.7702) were found for the treated water. For IBAC process there are also more advantages such as long backwashing cycle time, low backwashing intensity and prolonging activated carbon lifetime and so on.

Improving AOC degradation rate by intensified biological process in advanced water treatment

The object of is to evaluate assimilable organic carbon（AOC） degradation rate by intensified biological technique in advanced water treatment. By artificially acclimating and cultivating strains attached onto carbon surface, the selected strains can be intensified for their degradation to organic matters. The research indicates that ozonation process increases AOC concentration considerably, however, it is beneficial to microdegradation. Temperature and empty bed contact time （ TEBC ） are two important factors affecting microbiology. From 14 to 27 ℃, intensified biological carbon can remove AOC better compared with granular activated carbon （GAC）. Under identical TERC, intensified technique increases more than 10% AOC reduction.

Development of Primary Percutaneous Coronary Intervention as a National Reperfusion Strategy for Patients with ST-Elevation Myocardial Infarction and Assessment of Its Use in Egypt

Objective:Early treatment of acute ischemia of the heart by performing immediate percutaneous coronary intervention(PCI)to restore blood fl ow in patients with the clinical presentation of an acute coronary syndrome and more specifi cally with ST-elevation myocardial infarction(STEMI)can save lives.This study aims to identify the mean time(door to balloon time and fi rst contact to balloon time)to primary PCI for STEMI patients and to assess the percentage of primary PCI and its success rate in Egypt.Methods:A registry study of patients presenting to cardiac centers in Egypt was designed,where patients’basic characteristics,the treatment strategy,and the door to balloon time and the fi rst contact to balloon time were assessed.Results:One thousand six hundred fi fty STEMI patients with a mean age of 57 years were included in the study.Immediate transfer for primary PCI was the most used treatment strategy,representing 74.6%of all treatment strategies used.The door to balloon time and the fi rst contact to balloon time were 50 and 60 minutes,respectively,with a primary PCI success rate of 65.1%.Conclusion:The registry study results showed a marked improvement by implementation of the best treatment strategy with respect to the time factor to achieve a better outcome for STEMI patients in Egypt.

Cr （Ⅲ） Removal from Synthetic Waste Water by Using Water Pond Mud

The pollution of aquatic ecosystem by heavy metals has assumed serious proportions due to their toxicity and accumulative behavior. The toxicity metal is dependent on its chemical form and therefore removal of metal is more meaningful than the estimation of its concentrations. In this study, the batch experiments were carried out under 30℃ to study the effect of pH, initial Cr concentration, adsorbent dose and contact time on the removal of Cr （lII）. The maximum adsorption efficiency （99%） was observed when 1.5 g of pond mud was used for removal ofCr （Ⅲ） from test solution containing 150 mg·Cr / 100 ml. The optimal pH and contact time recorded during the study were 6 and 10.0, respectively.

Mechanical Behaviors of TiNi Alloy under Dynamic Impact Loading Conditions

The mechanical behaviors of Ti-50.7%Ni shape memory alloy under a dynamic impact loading condition were investigated by a home-built impact testing system. Both the contact force and the contact time during the impact process were measured with a piezoelectric force sensor and a digital signal processing system in real time. The predicted instantaneous velocity and the displacement formulae are presented. Results show that the maximum contact force increased, while the contact time decreased with the increase of the temperature when the TiNi alloy was in a martensitic state. When the compressive stress during the impact process was higher than the critical stress of the stress-induced martensitic transformation, the TiNi alloy specimen in the parent phase left no permanent deformation but could dissipate the impact energy.

Temperature in High Temperature SHPB Experiments

As an experimental technique, it’s desired that the temperature in specimen is uniform in high temperature split Hopkinson pressure bar (SHPB) experiments. However, the temperature in specimen decreases and the temperature of bars increases when specimen starts to contact with bars, which induces the nonuniform temperature distribution in specimen, and may result in inac-curacy of experimental results. In this paper, the temperature distributions of specimen and bars in high temperature SHPB experiments were investigated while the specimen was heated alone. Firstly, the temperature history of specimen was measured at different initial temperatures by ex-periments, then simulation was carried out. Simulation results were consistent with experimental results by adjusting the thermal contact coefficient between specimen and bars. By this way, the thermal contact coefficient and simulation results were validated, and the proper cold contact times of specimen and bars in high temperature SHPB experiments were discussed. Finally, the results were compared with those in references.

Kinetic Study for Adsorption of Heavy Metals on Zeolite

Heavy metals⁃polluted water has negative impact on the ecosystem.In Malaysia,minimum discharge limit for Cu^(2+)and Zn^(2+)are 1 mg/L and 2 mg/L,respectively.Zeolite is a highly porous adsorbent and its performance is affected by various factors,including contact time and pH.Thus,the objective of this study is to identify an ideal operating condition to treat Cu^(2+)and Zn^(2+)solutions up to the allowable discharge limit,by considering the pH and contact time factors.Six kinetic models were studied to identify the adsorption mechanism of the heavy metal removal process.Single solute batch adsorption experiment was conducted within pH 3-11 from 30 to 150 min.Results showed that hydration enthalpy(ΔHhyd)governed the selectivity of heavy metals,where a maximum of 90.87%Zn^(2+)(ΔH_(hyd)=-1955 kJ/mol)and 82.15%Cu^(2+)(ΔH_(hyd)=-2010 kJ/mol)removals were found at pH≥7.Without pH adjustment,selectivity towards Cu^(2+)was higher compared with Zn^(2+)due to the size of hydration radii,where Cu^(2+)is 0.11Åsmaller than Zn^(2+).By considering both pH and contact time factors,this study shows that by adjusting the pH of Zn^(2+)solutions to a minimum pH value of 7,the contact time required to achieve maximum Zn^(2+)removal rate was 90%,which can be achieved within 60 min.Meanwhile,zeolite performed better in Cu^(2+)removal without any pH adjustment where a maximum of 94%was achieved at 120 min.Final concentration of 0.523 mg/L Cu^(2+)and 0.981 mg/L Zn^(2+)were obtained in this study.Kinetic study showed that Ritchie’s equation predicted Cu^(2+)adsorption the best,while Zn^(2+)adsorption could be represented by Elovich model.This suggested that the adsorption on the activate site governed Cu^(2+)and Zn^(2+)removal process.Hence,future work should focus on modifying zeolite surface to improve the adsorptive performance.

Removal of disinfection by-product formation potentials by biologically assisted GAC treatment

The object of this paper is to evaluate the removal of disinfection by-products formation potential by artificially intensified biological activated carbon（BAC） process which is developed on the basis of traditional ozone granular activated carbon （GAC）. The results show that 23.1% of trihalomethane formation potential （THMFP） and 68% of haloacetic acid formation potential （HAAFP） can be removed by BAC, respectively. Under the same conditions, the removal rates of the same substances were 12.2% and 13-25% respectively only by GAC process. Compared with GAC, the high removal rates of the two formed potential substances were due to the increasing of bioactivity of the media and the synergistic capabilities of biological degradation cooperating with activated carbon adsorption of organic compounds. BAC process has some advantages such as long backwashing cycle time, low backwashing intensity and prolonged activated carbon lifetime, etc.

A Comparison of 3D Methods for Identifying the Stance Phase in Treadmill Running for Both Rearfoot and Forefoot Runners

We compared six 3D methods, OptoGait, and Myotest Run for the determination of contact time for runners with different foot strike patterns. Twenty male participants were divided into two groups： the heel group, who attack the ground with the heel （n = 12）, and the toe group, who attack the ground with the middle/front of the foot （n = 8）. They performed trials at speeds of 8 km/h then 16 km/h. To detect foot strike, the use of peak velocity of 3D markers located on the heel, the fifth metatarsal, and the great toe provided the best results for both groups. To detect the toe off, the minimum vertical position of a 3D marker placed in line with the great toe gave the most satisfactory results for both groups. In this way, the values of contact time measured with the 3D methods are consistent. Values measured with OptoGait appear consistent too, while those of the Myotest Run underestimate the contact time for both speeds. 3D analysis provides interesting opportunities for calculation of contact time for both rearfoot and forefoot runners, using specific peak velocities to determine foot strike and marker displacement to determine toe off.

A balancing act: Optimizing free chlorine contact time to minimize iodo-DBPs, NDMA, and regulated DBPs in chloraminated drinking water

Many drinking water treatment plants in the U.S. have switched from chlorination to chloramination to lower levels of regulated trihalomethane(THM) and haloacetic acid(HAA) disinfection byproducts(DBPs) in drinking water and meet the current regulations. However, chloramination can also produce other highly toxic/carcinogenic, unregulated DBPs: iodoacids, iodo-THMs, and N-nitrosodimethylamine(NDMA). In practice, chloramines are generated by the addition of chlorine with ammonia, and plants use varying amounts of free chlorine contact time prior to ammonia addition to effectively kill pathogens and meet DBP regulations. However, iodo-DBPs and nitrosamines are generally not considered in this balancing of free chlorine contact time. The goal of our work was to determine whether an optimal free chlorine contact time could be established in which iodo-DBPs and NDMA could be minimized, while keeping regulated THMs and HAAs below their regulatory limits. The effect of free chlorine contact time was evaluated for the formation of six iodo-trihalomethanes(iodo-THMs), six iodo-acids, and NDMA during the chloramination of drinking water. Ten different free chlorine contact times were examined for two source waters with different dissolved organic carbon(DOC) and bromide/iodide. For the low DOC water at pH 7 and 8, an optimized free chlorine contact time of up to 1 h could control regulated THMs and HAAs, as well as iodo-DBPs and NDMA. For the high DOC water, a free chlorine contact time of 5 min could control iodo-DBPs and NDMA at both p Hs, but the regulated DBPs could exceed the regulations at pH 7.

SIR model with time-varying contact rate

The contact rate is defined as the average number of contacts adequate for disease transmission by an individual per unit time and it is usually assumed to be constant in time.However,in reality,the contact rate is not always constant throughout the year due to different factors such as population behavior,environmental factors and many others.In the case of serious diseases with a high level of infection,the population tends to reduce their contacts in the hope of reducing the risk of infection.Therofore,it is more realistic to consider it to be a function of time.In particular,the study of models with contact rates decreasing in time is well worth exploring.In this paper,an SIR model with a time-varying contact rate is considered.A new form of a contact rate that decreases in time from its initial value till it reaches a certain level and then remains constant is proposed.The proposed form includes two important parameters,which represent how far and how fast the contact rate is reduced.These two parameters are found to play important roles in disease dynamics.The existence and local stability of the equilibria of the model are analyzed.Results on the global stability of disease-free equilibrium and transcritical bifurcation are proved.Numerical simulations are presented to illustrate the theoretical results and to demonstrate the effect of the model parameters related to the behavior of the contact rate on the model dynamics.Finally,comparisons between the constant,variable contact rate and variable contact rate with delay in response cases are presented.

Performance of biotrickling filters packed with structured or cubic polyurethane sponges for VOC removal

Two identical bench-scale biotrickling filters （BTFs）, BTF 1 and BTF 2, were evaluated for toluene removal at various gas empty bed contact times （EBCTs） and organic loadings. BTF 1 and BTF 2 were packed with structured and cubic synthetic polyurethane sponges, respectively. At a constant toluene loading of 16 g/（m3.hr）, toluene removal efficiencies decreased from 98.8% to 64.3% for BTF 1 and from 98.4% to 74.1% for BTF 2 as gas EBCT decreased from 30 to 5 sec. When the toluene loading increased from 35 to 140 g/（m3.hr） at a gas EBCT of 30 sec, the removal efficiencies decreased from 99.1% to 77.4% for BTF 1 and from 99.0% to 81.5% for BTF 2. The pressure drop for both BTFs increased with increased air flow rate, and did not significantly vary while the toluene loading was increased under similar operation conditions. BTF 1 and BTF 2 could start up successfully within 19 and 27 days, respectively, when packed with fresh sponge media, and the performances could be restored in 3-7 days after biomass was removed and wasted from the media. BTF 2 displayed higher removal efficiency even under shorter EBCT or higher loading rate than BTF1 when other operation conditions were similar, while it showed lower pressure drop than BTF 1 during the whole period of operation. These results demonstrated that both BTFs could treat waste gas containing toluene effectively.

Effect of Feather Elasticity of Kingfisher Wing on Droplet Impact Dynamics

We experimentally studied droplet impact dynamics onto wing feathers of kingfishers. Distilled water droplets with a fixed diameter of 2.06 mm were used as drop liquid and the initial impact velocities of droplets varied from 0.28 m· s^-1 to 1.60 m·s^-1. Two high-speed cameras were utilized to capture the impact process of water droplets onto the wing feather surface from both horizontal and vertical directions. Two states of the feathers （elastic and inelastic） were considered to study the influence of elasticity. At the entire impact ve- locity range we studied, regular rebound, bubble trapping and jetting, partial pinning and partial rebound of droplets on inelastic wing feather surface were observed as the initial impact velocity increased. However, only one dynamic behavior （regular rebound） was found on the elastic wing feather surface. The elasticity plays a more important role in the direction difference of droplet spreading than wing feather microstructure. The contact time of water droplets on the elastic wing feather surface was less than that on the inelastic surface within the range of Web numbers from 1.06 to 36 under test conditions.

Arsenite Removal from Simulated Groundwater by Biogenic Schwertmannite: A Column Trial

To assess the feasibility of biogenic schwertmannite to act as a sorbent for removing arsenite from groundwater, a series of biogenic schwertmannite-packed column adsorption experiments were conducted on simulated As（III）-containing groundwater. Empty bed contact time （EBCT）, As（III） concentration in effluent, and the removal efficiency of As（III） through the column were investigated at pH 8.0 and temperature 25 ± 0.5 ℃. The results showed that the breakthrough curves were mainly dependent on EBCT values when the influent As（III） concentration was 500 μg L-1 and the optimum EBCT was 4.0 min. When the effluent As（III） concentration reached 10 and 50 μg L-1, the breakthrough volumes for the schwertmannite adsorption column were 4200 and 5600 bed volume （BV）, with As（III） adsorption capacity of 2.1 and 2.8 mg g-1, respectively. Biogenic schwertmannite could be regenerated by 1.0 mol L-1 NaOH solution, and more than 80% of As（III） adsorbed on the surface of schwertmannite could be released after 3 successive regenerations. The breakthrough volume for the regenerated sehwertmannite-packed column still maintained 4 000-4 200 BV when the As（III） concentration in effluent was below 10 μg L-1. Compared with other sorbents for As（III） removal, the biogenic schwertmannite- packed column had a higher breakthrough volume and a much higher adsorption capacity, implying that biogenic schwertmannite was a highly efficient and potential sorbent to purify As（III）-contaminated groundwater.

A review on treatment of disinfection byproduct precursors by biological activated carbon process

Disinfection by-products(DBPs)in water systems have attracted increasing attention due to their toxic effects.Removal of precursors(mainly natural organic matter(NOM))prior to the disinfection process has been recognized as the ideal strategy to control the DBP levels.Currently,biological activated carbon(BAC)process is a highly recommended and prevalent process for treatment of DBP precursors in advanced water treatment.This paper first introduces the fundamental knowledge of BAC process,including the history,basic principles,typical process flow,and basic operational parameters.Then,the selection of BAC process for treatment of DBP precursors is explained in detail based on the comparative analysis of dominant water treatment technologies from the aspects of mechanisms for NOM removal as well as the treatability of different groups of DBP precursors.Next,a thorough overview is presented to summarize the recent developments and breakthroughs in the removal of DBP precursors using BAC process,and the contents involved include effect of pre-BAC ozonation,removal performance of various DBP precursors,toxicity risk reduction,fractional analysis of NOM,effect of empty bed contact time(EBCT)and engineered biofiltration.Finally,some recommendations are made to strengthen current research and address the knowledge gaps,including the issues of microbial mechanisms,toxicity evaluation,degradation kinetics and microbial products.