Toxic effect of sulfur compounds on anaerobic biogranule

The effects of sulfide, sulfite and sulfate on degradation of volatile fatty acid (VFA) in UASB process have been studied by using serum bottle assay and septage-leachate acclimated biogranules. The relative toxicity of the compounds towards methane production and degradation of total VFA varied as SO(4)(2-) -S>S(2-)>SO(3)(2-) -S and SO(4)(2-) -S>SO(3)(2-) -S>S(2-), respectively. The difference of this order shows the importance of choosing monitoring factor in evaluating the effect of sulfur compounds on a UASB system. For the individual VFA the effects of sulfur compounds depended on the types of VFA. The VFA-degrading activity of anaerobic biogranules was decreased by 50% when 34, 26 and 20mg of S(2-), SO(3)(2-) -S and SO(4)(2-) -S were added to each gram of biomass, respectively. A comparison of the toxicity-resistance between two different anaerobic biogranules that acclimatized with septage-leachate mixture and septage was also made.In the presence of the leachate, the toxicity-resistance of biogranules was not weakened to sulfide and sulfate but was enhanced to sulfite.     

A Real-time Monitoring Technique for Local Plasticity in Metals Based on Lamb Waves and a Directional Actuator/Sensor Set

A real-time monitoring technique for local plasticity using Lamb waves was developed. Tensile test of a thin aluminum plate with a circular hole where high stress concentration was induced was conducted to verify this technique. During the tensile test, a series of wave signals passing through the local plastic region were collected using a directional actuator/sensor set to monitor plasticity evolution. A pulse compression technique was used to process the wave signals. With the increase of tensile stress in the specimen, the amplitude changes of S₀ and A₀ modes were obtained and the difference of Lamb wave signals was further evaluated using a proposed signal index I calculated by wavelet analysis. Combined with the numerical stress analysis of the tensile specimen, the influence of the plasticity on the amplitudes of S₀ and A₀ wave modes was analyzed. As the plastic zone grows gradually, the wave amplitudes and I of S₀ and A₀ wave modes show their different change tendencies compared with those in elastic stage. The amplitude change is more sensitive to mild plasticity than that of I, while the change of I caused by severe plasticity is more obvious than the amplitude change.     

Pulsed NMR studies in solid D2. I. Solid echo

The solid echoes for both I = 1 and I = 2 nuclear spins from a two-pulse sequence are studied forp-D₂ concentrations between 0.06 and 0.5 and for 0.06 < T < 1.5 K. The drop of the I = 1 echo amplitude from Curie's law reported earlier is confirmed and is discussed. The density matrix method, previously developed to describe the I = 1 echo properties in solid H₂ as a function of various parameters, is applied to p-D₂, and similarly accounts for most of the observations. An analysis of the I =2 echoes for o-D₂ is carried out in similar fashion in the absence of a complete density matrix theory. Studies of the echo amplitude for the I = 1 and I = 2 spins versus r.f. pulse widths are reported and discussed. Various measurements associated with the echo decay as a function of the time between the two r.f. pulses are described. They include the I = 2 echo maximum shift respective to that of I = 1, the echo amplitude ratio S (I = 1)/S(I =2), the intermodular nuclear interaction magnitude, the local inhomogeneous field distribution, and the absence of expected satellite echoes for I =2. A comparison is made with the results of a similar study on solid H₂.     

Kinetics of fly ash geopolymerization

Based on the wet chemical analysis, we measured and modeled the kinetics of reactions between fly ash and KOH at various temperatures and water-to-solid mass ratios (W/S). We find that three consecutive rate-limiting processes control reaction progress: (1) dissolution or alteration of the glass phase in the fly ash, (2) classical Fick diffusion through a surface layer, and (3) diffusive transport through a more complex gel structure (interstitial gel). This sequence of processes is independent of W/S (0.35–40), temperature (22–75 °C), and KOH concentration (5–10 M). The relative contribution of each process to the overall reaction progress changes with experimental conditions. Only if and when the third process is rate limiting, a fly ash geopolymer forms and develops mechanical strength (sufficiently low W/S ratio provided). The rate of reaction progress decreases significantly, due to slow transport of reacting species to the surface of the glass particles.     

Orientational ordering in solid D2 from NMR studies. II. The cubic ordered phase

An NMR study in the cubic phase of D₂ which exhibits long-range orientational order is reported. The spin systems in both para D₂ (with angular momentum J=1 and spinI=1) and in ortho D₂ (with J=0 andI=2) were investigated. The integrated intensity ratio of theI=1 andI=2 components in the solid echo, the NMR line shapes obtained by Fourier transforming the solid echoes, and the longitudinal relaxation times for theI=1 andI=2 systems are presented. Samples with D₂ concentrationX between 0.69 and 0.62 were studied over the temperature range 0.12<T<4 K. Measurements were carried out before and after repeated thermal cycling through the ordering transition to study the effect of this cycling on the temperature dependence of the relaxation times. The complex behavior of these relaxation times was found to be similar to that in cubic H₂ at a comparable concentration, and the interpretation of this behavior is discussed. Over most of the temperature range, the relaxation time of theI=2 spins is larger than that of theI=1 spins and is believed to be determined by cross-relaxation with the latter, whose intrinsic spin-lattice relaxation is observed. However, at low enough temperatures, the relaxation time for theI=2 spins is found to be shorter than that for theI=1 spins, and this observation cannot be understood on the basis of predictions. Furthermore, theI=2 relaxation time in this temperature region is found to depend on the position within the NMR line. Another observation not yet understood is that the ratio of the integrated intensitiesS(I=1)/S(I=2) in the solid echo is smaller than the theoretically predicted one by about 20%. The NMR line shapes for theI=1 spins in the ordered phase obtained from pulse measurements are compared with those from continuous-wave methods and to those from H₂.     

AnMBR处理活性黑KN-B印染废水

实验对厌氧膜生物反应器(AnMBR)处理活性黑KN-B印染废水进行了探讨.研究了厌氧反应器内活性污泥的驯化培养状况,考察了厌氧反应器与管式超滤膜对印染废水BOD5,COD的去除作用,并对厌氧反应器产气量、出水的碳酸氢盐碱度和VFA进行了分析,通过UV-Vis光谱图分析了AnMBR对活性黑KN-B的脱色效果.结果表明,液流较低的低负荷启动方式使该AnMBR活性污泥的驯化培养顺利进行,厌氧反应器污泥床区域的污泥浓度培养至35 g/L;AnMBR对废水BOD5和COD的去除率分别达到90%和85%以上;该厌氧反应器的活性污泥体系和缓冲体系相对稳定,出水的碳酸氢盐碱度和VFA分别在16~18mmol/L与1.0~3.5 mmol/L的范围内波动,pH稳定在7.70~8.00之间;AnMBR对500mg/L的活性黑KN-B废水的脱色率能达到90%以上.     

Compression fatigue performance of a fire resistant syntactic foam

Compression–compression fatigue test study of a fire resistant Eco-Core was conducted at two values of stress ratios (R = 10 and 5). Tests were conducted at S_min/S_o values of 0.9–0.6 for R = 10 and 0.95–0.8 for R = 5. Here S_min is the maximum compression stress and S_o is the compression strength. The study showed that Eco-Core has well defined failure modes and associated fatigue lives. The failure modes are: damage on-set; damage progression, and final failure. The damage on-set, propagation and final failure were characterized by 2%, 5% and 7% changes in compliance. The three failure modes were found to be same for both static and fatigue loadings. The endurance limit was found to be 0.72S_o, 0.75S_o and 0.76S_o, respectively for three failure modes for R = 10 and 0.81S_o, 0.82S_o and 0.82S_o, respectively for R = 5. The fatigue life is defined by a power law equation, S_min/S_o = A_oN^α. Constants of the equation were established for all three modes of failures and the two stress ratios. Finally, fatigue life was found to be less sensitive to R ratio when expressed in terms of stress range versus number of load cycles, which is similar to that of metallic materials.     

High‐Responsivity Graphene/InAs Nanowire Heterojunction Near‐Infrared Photodetectors with Distinct Photocurrent On/Off Ratios

Graphene is a promising candidate material for high‐speed and ultra‐broadband photodetectors. However, graphene‐based photodetectors suffer from low photoreponsivity and I_light/I_dark ratios due to their negligible‐gap nature and small optical absorption. Here, a new type of graphene/InAs nanowire (NW) vertically stacked heterojunction infrared photodetector is reported, with a large photoresponsivity of 0.5 AW^?1 and I_light/I_dark ratio of 5 × 10², while the photoresponsivity and I_light/I_dark ratio of graphene infrared photodetectors are 0.1 mAW^?1 and 1, respectively. The Fermi level (E_F ) of graphene can be widely tuned by the gate voltage owing to its 2D nature. As a result, the back‐gated bias can modulate the Schottky barrier (SB) height at the interface between graphene and InAs NWs. Simulations further demonstrate the rectification behavior of graphene/InAs NW heterojunctions and the tunable SB controls charge transport across the vertically stacked heterostructure. The results address key challenges for graphene‐based infrared detectors, and are promising for the development of graphene electronic and optoelectronic applications.     

Compartmentalizing anaerobic zone improves sludge settling property of enhanced biological phosphorus removal system under low sludge retention time

Abstract

The study investigated the effect of compartmentalization of anaerobic zone on sludge settling property in an enhanced biological phosphorus removal (EBPR) system. Continuous‐flow pilot‐plant experiments with synthetic influent were performed at varied anaerobic‐oxic volume ratios (V_an : V_o , 1 : 9 and 2 : 8), involving 5, 10 and 15 days of sludge retention times (SRTs). Experimental results indicated that, regardless of V_an : V_o and SRT, satisfactory removal of COD and phosphate were achieved during all test runs. However, extremely high sludge volume index (SVI) values were observed when there were 5 days of SRT. Further experiments with compartmentalization of anaerobic zone were therefore conducted to confirm the necessity of incorporating the kinetic selection mechanism of bulking control into an EBPR process operated at a low SRT. These results revealed that the two factors, V_an : V_o and anaerobic compartmentalization, had interaction with respect to sludge settling property in terms of SVI. When anaerobic retention time increased from 0.72hr to 1.36hr, compartmentalizing anaerobic zone significantly decreased the SVI value because of generating high COD concentration gradient and phosphate release in the anaerobic zone. This result implies that supplementing kinetic selection pressure of bulking control exhibits a critical influence on sludge settling when the EBPR process operates at a lower SRT.     

On the theory of resistive states in superconductors

The contribution R _s of a superconductor S to the resistance of a superconductor-normal metal (S-N) system is calculated. The case when the characteristics of metals S and N are different (different mean free path, density of states, etc.) is considered. It is shown that the value and temperature dependence of R _s differ from those obtained earlier. The resistance of the S-N-S system and of a system consisting of alternating S-N layers is calculated. The excess current I _exc in contacts S₁-c-S₂ (S_1,2 are different superconductors, c denotes a narrow constriction) is determined. The influence of magnetic field and of paramagnetic impurities on the value of the I _exc is found.     

A design for intrinsic control of anaerobic digestion

The article reports on a novel layout which achieves intrinsic control of anaerobic digestion of a wide range of feeds on a continuous basis. The feed is automatically controlled to match the digestion rate. The design consists of a shallow tank concentric with a gas holder resting on stoppers on the tank bottom. The height of the digesting fluid is maintained using the plug flow principle. The feed material is dropped into the annular space which is thereafter covered with a black plastic sheet to enable anoxic conditions to prevail. The bioliquid hydrolyses the material, with the help of prefermenting bacteria, into volatile acids. A steady migration of these volatile acids into the anaerobic digester is maintained by the concentration gradient, which is constantly replenished by the action of a syntrophic community of bacteria, producing methane. Further, the feasibility of the concept is reported on a system with a 45 m³ concrete tank and a 35 m³ steel gas holder by using a mix of domestic wastes and producing gas with 70% methane content reliably for hundred days continuously. A novel simulator is developed to predict the performance of the design at various parameters of operation. It is shown that the performance data for digesters analogous to the design reported here are interchangeable. Based on this, the average productivity of gas for various loadings is predicted within ±10% of the actual yields for the analogous digesters. Because of the nature of the design, digestion of a wide range of feeds are permitted: without the problems faced in conventional layouts. This tremendous potential is realised by maintaining the integrity of the ecosystem of anaerobic digestion through the medium of the bioliquid which pervades the annular space as well as the confines of the anaerobic digester. By utilising the design in practice at normal loadings, its potential for reliable and economic digestion at a fraction of the cost of deep digesters could be realised if the predictions are confirmed at higher loadings by further work. This work has been carried out in the Tata Electric Companies partly in the program on renewable resources.     

Effect of solid polymer electrolyte on the sensitization of photocurrents in solid-state electrochemical cells using conducting polypyrrole

The effect of small concentration of methylene blue dye on photocurrents was studied in the solid-state photoelectrochemical cells fabricated using conducting polypyrrole-coated electrodes sandwiched with solid-polymer electrolyte, namely, polyvinylpyrrolidone with phosphoric acid. A maximum photosensitivity factor (S=I _l/I _d, where I _l is the photocurrent and I _d is the dark current) of the order of 5 is observed. The current–voltage (I–V) characteristics in such cells reveal that charge transport is mainly governed by the space charge effect. Comparison of the results presented in this paper with the ones we reported earlier [23] indicates that the matrix in which dye has been incorporated plays an important role in such sensitization processes. A matrix that can efficiently transport the photogenerated charge carriers is observed to be more suitable for such dye-sensitized devices.     

Short fatigue crack growth behavior under mixed-mode loading

Mixed-mode loading represents the true loading condition in many practical situations. In addition, most of the fatigue life of many components is often spent in the short crack growth stage. The study of short crack growth behavior under mixed-mode loading has, therefore, much practical significance. This work investigated short crack growth behavior under mixed-mode loading using a common medium carbon steel. The effects of load mixity, crack closure, and load ratio on short crack growth behavior were evaluated by conducting experiments using four-point bending specimens with several initial K _II /K _I mixed-mode ratios and two load ratios. Cracks were observed to grow along the paths with very small K _II /K _I ratios (i.e. mode I). The maximum tangential stress criterion was used to predict the crack growth paths and the predictions were found to be close to the experimental observations. Several parameters including equivalent stress intensity factor range and effective stress intensity factor range were used to correlate short crack growth rates under mixed-mode loading. Threshold values for short cracks were found to be lower than those for long cracks for all the mixed-mode loading conditions. Crack closure was observed for the entire crack length regime with all load mixity conditions at R ≈ 0.05 and for short crack regime under high load mixity condition at R = 0.5. Several models were used to describe mean stress effects and to correlate crack growth rate data.     

Experimental study and modeling of fatigue life prediction of plain weave carbon/polymer composite under constant amplitude loading

For fiber-reinforced composites, the anisotropy and the tension-compression asymmetry have very important influence on fatigue performance. The quasi-static and fatigue mechanical behavior of plain weave laminates of carbon/polymer composites were experimentally investigated in this paper. The quasi-static and stress-controlled fatigue tests were carried out on the servo-hydraulic material testing machine. Fracture failure surfaces were observed in micro-mechanism with scanning electron microscopy. A phenomenological and nonlinear constant life diagram (CLD) model was developed based on quasi-static strength and S–N curve data-sets of different stress ratios. The relationship between six parameters of the proposed model and the failure cycles was studied. The fatigue experimental results showed that the fatigue failure type changed from tensile mode to compressive mode at nearby stress ratio R = ?0.2. A satisfactory agreement between the predicted value of cycle life and experimental data was observed. The results indicated that the fatigue performance was adequately described by the Basquin S–N formulation and proposed CLD.     

Polymer coating for filamentary YBa2Cu3Ox superconductors

Polymer coating for filamentary YBa₂Cu₃O _x superconductors was examined. The precursor filaments were prepared by solution spinning through aqueous poly(vinyl alcohol) solution containing mixed acetates of Y, Ba and Cu. The as-drawn filaments were heated to remove volatile components and to generate a superconducting phase. The synthesis of polyamide acid for the polymer coating was made. The filamentary superconductors were coated with the polyamide acid and cured to convert to the polyimide. The surface of the sample was an insulator. The critical current (I _c) value of the filamentary sample at 77 K was preserved by the polyimide coating. Moreover, the I _c for the polyimide-coated sample was maintained after holding at room temperature for more than 6 months. After thermal cycling between 77 K and room temperature 10 times, the I _c for the coated sample did not deteriorate, whereas the I _c for the sample without polymer coating disappeared. Polymer coating using epoxy resin applied to the filamentary superconductors was also examined.     

Effect of increasing nitrobenzene loading rates on the performance of anaerobic migrating blanket reactor and sequential anaerobic migrating blanket reactor/completely stirred tank reactor system

A laboratory scale anaerobic migrating blanket reactor (AMBR) reactor was operated at nitrobenzene (NB) loading rates increasing from 3.33 to 66.67 g NB/m³ day and at a constant hydraulic retention time (HRT) of 6 days to observe the effects of increasing NB concentrations on chemical oxygen demand (COD), NB removal efficiencies, bicarbonate alkalinity, volatile fatty acid (VFA) accumulation and methane gas percentage. Moreover, the effect of an aerobic completely stirred tank reactor (CSTR) reactor, following the anaerobic reactor, on treatment efficiencies was also investigated. Approximately 91–94% COD removal efficiencies were observed up to a NB loading rate of 30.00 g/m³ day in the AMBR reactor. The COD removal efficiencies decreased from 91% to 85% at a NB loading rate of 66.67 g/m³ day. NB removal efficiencies were approximately 100% at all NB loading rates. The maximum total gas, methane gas productions and methane percentage were found to be 4.1, 2.6 l/day and 59%, respectively, at a NB loading rate of 30.00 g/m³ day. The optimum pH values were found to be between 7.2 and 8.4 for maximum methanogenesis. The total volatile fatty acid (TVFA) concentrations in the effluent were 110 and 70 mg/l in the first and second compartments at NB loading rates as high as 66.67 and 6.67 g/m³ day, respectively, while they were measured as zero in the effluent of the AMBR reactor. In this study, from 180 mg/l NB 66 mg/l aniline was produced in the anaerobic reactor while aniline was completely removed and transformed to 2 mg/l of cathechol in the aerobic CSTR reactor. Overall COD removal efficiencies were found to be 95% and 99% for NB loading rates of 3.33 and 66.67 g/m³ day in the sequential anaerobic AMBR/aerobic CSTR reactor system, respectively. The toxicity tests performed with Photobacterium phosphoreum (LCK 480, LUMIStox) and Daphnia magna showed that the toxicity decreased with anaerobic/aerobic sequential reactor system from the influent, anaerobic and to aerobic effluents.     

Flexural fatigue of short glass fiber reinforced a blend of polyphenylene ether ketone and polyphenylene sulfide

Flexural fatigue tests were conducted on injection molded glass fiber reinforced a blend of polyphenylene ether ketone and polyphenylene sulfide composite using four-point bending with different stress ratios and different frequencies. The fatigue behavior of this material was described. The constructed S-N curves shift their trends obviously at the maximum cyclic stress being about 80% of the ultimate flexural strength. Examinations of failure surfaces for various loading conditions show that the fatigue failure mechanisms appear to be matrix yielding at high stresses and crack growth at low stresses. Analyses of the fatigue data at various stress ratios reveal that the data at low stress superimpose to form a single curve which is nearly linear when they are plotted as stress range versus number of cycles to failure in bilogarithmic axes, while the data at high stresses also converge to yield a single curve when they are plotted as (S _max S _range)^1/2 against specimen lifetimes (S _max is the maximum stress andS _range is the stress range). These results show that for the studied material the main factor influencing the lifetime is the stress range at low stresses and the parameter (S _max S _range)^1/2 at high stresses. Comparison of fatigue data in the frequency range of 0.89–7.0 Hz was made, no significant effect of frequency on the fatigue behavior is found.     

Signal Output of Triboelectric Nanogenerator at Oil–Water–Solid Multiphase Interfaces and its Application for Dual‐Signal Chemical Sensing

A liquid–solid contact triboelectric nanogenerator (TENG) based on poly(tetrafluoroethylene) (PTFE) film, a copper electrode, and a glass substrate for harvesting energy in oil/water multiphases is reported. There are two distinctive signals being generated, one is from the contact electrification and electrostatic induction between the liquid (water/oil) and the PTFE film (V_TENG and I_TENG); and the other is from the electrostatic induction in the copper electrode by the oil/water interfacial charges (ΔV_interface and I_interface), which is generated only when the liquid–solid contact TENG is inserted across the oil/water interface. The two signals show interesting opposite changing trends that the V_TENG and I_TENG decrease while the oil/water interfacial signals of ΔV_interface and I_interface increase after coating a layer of polydopamine on the surfaces of PTFE and glass via self‐polymerization. As an application of the observed phenomena, both the values of I_TENG and I_interface have a good linear relationship versus the natural logarithm of the concentration of the dopamine. Based on this, the first self‐powered dual‐signal detection of dopamine using TENG is demonstrated.     

Relaxation of the distribution function branch imbalance Q * in Sn and Sn-In alloys

We have used double tunnel junctions M₁-S₂-N₃ to measure the detector junction (S₂-N₃) voltage at zero detector current V _d(0) vs. generator junction (M₁-S₂) current I _g for samples cooled by helium exchange gas. We find terms both symmetric V _d ^S(0; I _g ²) and asymmetric V _d ^A(0; I _g) in I _g. The term V _d ^S is attributed to a thermoelectric voltage generated in the sample; V _d ^A is produced by Q ^*, the distribution function branch imbalance, in S₂. We have analyzed Q ^* relaxation in these samples and have compared the results with those obtained earlier by Paterson. For Sn and Sn : In alloys we find % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeqiXdq3aaS% baaSqaaGqaaiaa-ffacaWFQaaabeaakiabg2da9Gqaciaa+fdacaGF% UaGaa4xmaiaa+flacaGFWaGaa4Nlaiaa+jdacaGFxdGaa4xmaiaa+b% dadaahaaWcbeqaaiaa+1cacaGFXaGaa4hmaaaakiabfs5aejaacIca% caGFWaGaaiykaiaac+cacqqHuoarcaGGOaGaa8hvaiaacMcaaaa!4C83!\[\tau _{Q*} = 1.1 \pm 0.2 \times 10^{ - 10} \Delta (0)/\Delta (T)\] sec for T - T _c; the data at all temperatures have been compared with the calculations by Chang. The attempt to measure % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeqiXdq3aaS% baaSqaaGqaaiaa-ffacaWFQaaabeaaaaa!3964!\[\tau _{Q*} \] in Pb near T _c is discussed and data are presented for V _d ^S for Pb.Supported by grants from the Research Corporation and the National Science Foundation (DMR 74-23661).     

Infrared-to-visible upconversion flurescence of Er/Yb-codoped bismuthate glasses

Er³⁺/Yb³⁺-codoped bismuthate glasses for developing potential upconversion lasers have been fabricated and characterized. The optimal Yb³⁺ doping content was investigated in the glasses with different Yb³⁺-Er³⁺ concentration ratios and the optimal Yb³⁺-Er³⁺ concentration ratio is 5:1. Under 975 nm excitation, intense green and red emissions centered at 525, 546 and 657 nm, corresponding to the transitions ²H_11/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 → ⁴I_15/2, respectively, were observed at room temperature. The quadratic dependence of the 525, 546 and 657 nm emissions on excitation power indicates that a two-photon absorption process occurs under 975 nm excitation.