Change In Loading Rate Research Articles

APPLICATION OF DYNAMIC MODELING TO ASSESS IMPACT OF TRANSIENT VARIATIONS ON DENITRIFICATION PERFORMANCE OF UPFLOW CONTINUOUS BACKWASH FILTERS

APPLICATION OF DYNAMIC MODELING TO ASSESS IMPACT OF TRANSIENT VARIATIONS ON DENITRIFICATION PERFORMANCE OF UPFLOW CONTINUOUS BACKWASH FILTERSIn order to meet very low nitrogen limits, denitrification filters are often designed conservatively to account for variations in actual operating conditions that may impact performance. Under full-scale conditions, the filters can be exposed to significant changes in loading rates due to diurnal variations, wet weather events, and upsets in upstream processes at the wastewater treatment plant...Author(s)P. SchauerC. deBarbadilloA. R. ShawB. SabherwalR. RectanusSourceProceedings of the Water Environment FederationSubjectSession 12: Special Panel Session: Nutrient Removal ModelingDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2007ISSN1938-6478SICI1938-6478(20070101)2007:2L.1224;1-DOI10.2175/193864707787976524Volume / Issue2007 / 2Content sourceNutrient Removal and Recovery SymposiumFirst / last page(s)1224 - 1242Copyright2007Word count295

Olivine friction at the base of oceanic seismogenic zones

We investigate the strength and frictional behavior of olivine aggregates at temperatures and effective confining pressures similar to those at the base of the seismogenic zone on a typical ridge transform fault. Triaxial compression tests were conducted on dry olivine powder (grain size ≤60 μm) at effective confining pressures between 50 and 300 MPa (using Argon as a pore fluid), temperatures between 600°C and 1000°C, and axial displacement rates from 0.06 to 60 μm/s (axial strain rates from 3 × 10−6 to 3 × 10−3 s−1). Yielding shows a negative pressure dependence, consistent with predictions for shear enhanced compaction and with the observation that samples exhibit compaction during the initial stages of the experiments. A combination of mechanical data and microstructural observations demonstrate that deformation was accommodated by frictional processes. Sample strengths were pressure‐dependent and nearly independent of temperature. Localized shear zones formed in initially homogeneous aggregates early in the experiments. The frictional response to changes in loading rate is well described by rate and state constitutive laws, with a transition from velocity‐weakening to velocity‐strengthening at 1000°C. Microstructural observations and physical models indicate that plastic yielding of asperities at high temperatures and low axial strain rates stabilizes frictional sliding. Extrapolation of our experimental data to geologic strain rates indicates that a transition from velocity weakening to velocity strengthening occurs at approximately 600°C, consistent with the focal depths of earthquakes in the oceanic lithosphere.

Echocardiograph-determined Left Ventricular Function Immediately After Prolonged Exercise

Exercise-induced acute cardiac fatigue (EACF) is characterised by a reduction in left ventricular function immediately following prolonged athletic events. Individual studies on EACF have involved small sample sizes (n<20) and have differed in the selected exercise duration and the training status of study participants. PURPOSE: To quantify, using meta-analytic procedures, the immediate impact of endurance exercise on left ventricular function, as determined by echocardiography, and explore possible moderating factors and mechanisms of EACF. METHODS: The results of 23 studies, involving a total of 413 participants, were collated. Using the inverse variance approach, a random-effects meta-analysis of the weighted mean acute changes in ejection fraction (EF), systolic blood pressure/end systolic volume ratio (SBP/ESV) and early to late diastolic filling ratio (E:A) was conducted. Mean exercise-induced changes in heart rate (HR), systolic blood pressure (SBP) and the internal diameter of the left ventricle during diastole (LVD) were also analysed. Ninety-five percent confidence limits (CL) of each mean change were calculated from the reported between-subjects standard deviations. The presence of study heterogeneity was followed-up with sub-group analyses using the moderator variables of training status ('trained' and 'untrained') and exercise duration; 'moderate' (60–151 min), 'long' (166–430 min) and 'ultra-long' (640–1440 min). RESULTS: The pooled CL for the immediate post-exercise reductions in EF, SBP/ESV and E:A were 1.03 to 2.88%, 0.63 to 0.97, and 0.39 to 0.51, respectively (p<0.05). The reduction in EF was most marked for untrained participants performing moderate exercise (CL = 3.08 to 7.85%). For the trained participants, exercise duration did not influence the generally smaller reductions in EF and E:A. Post-exercise changes in E:A were not related to those in LVD (r=0.25, p=0.451), HR (r= −0.35, p=0.198) or SBP (r= 0.16, p=0.585). CONCLUSIONS: Exercise-induced acute cardiac fatigue is most marked in untrained individuals after 1–3 hrs of physical activity. Well-trained athletes demonstrate smaller reductions in left ventricular function even immediately after ultra-endurance events. The acute decrease in ejection fraction and SBP/ESV indicates a transitory reduction in systolic function, which probably represents a reversible change in cardiac loading conditions. The decrease in diastolic filling that was found to be unrelated to changes in loading or heart rate may suggest a sub-clinical and transient impairment of left ventricular relaxation after prolonged exercise.

アルミニウム合金展伸材の吸収エネルギーと破壊表面積に及ぼす負荷速度の影響

The effect of loading rate on absorbed energy and fracture surface area of three types of wrought aluminum alloys, namely high toughness 5083-O and 6061-T651 alloys and low toughness 7075-T6 alloy are studied. A laser displacement measuring equipment and a scanning laser microscope are used in order to measure three-dimensional geometry of the fracture surface. Shear lip and plastic hinge can be observed in 5083-O and 6061-T651 aluminum alloys. According to a measuring region, the calibration factor K is notably different. Moreover, the calibrated fracture surface area of each fracture geometry changes considerably with increasing loading rate. On the other hand, in 7075-T6 aluminum alloy, macroscopic fracture geometries are not clearly defined, and almost no difference appears in the calibration factor K within the same fracture surface. Moreover, calibrated whole surface area increases linearly with increasing loading rate. In any aluminum alloys, the tends in the loading rate change of calibrated whole fracture surface area, AW, and the total absorbed energy, Et , with loading rate are similar each other. Therefore, the change of fracture surface area is one of the main factors that affect the change of absorbed energy.

Structural Determinants of Factor IX(a) Binding in Nitrophorin 2, a Lipocalin Inhibitor of the Intrinsic Coagulation Pathway

Nitrophorin 2 (NP2) is a salivary lipocalin from Rhodnius prolixus that binds with coagulation factors IX (fIX) and IXa (fIXa). Binding of NP2 with fIXa results in potent inhibition of the intrinsic factor Xase complex. A panel of site-directed surface mutants of NP2 was generated to locate determinants of high affinity fIX(a) binding. The locations of the mutations were based on comparisons with the related, but less potent, inhibitor nitrophorin 3 (NP3). Three point mutants (K21A, K92A, and V94A) were found that clearly reduced the inhibitory potency as measured by the activity of a reconstituted factor Xase system. Binding of NP2 with fIXa and fIX as measured by surface plasmon resonance and isothermal titration calorimetry was reduced in a similar manner. Of the three mutants, two (K92A and V94A) were located on the loop connecting beta-strands E and F of the lipocalin beta-barrel. The largest changes were seen with the K92A mutation, which lies at the apex of the loop, with a smaller effect being seen with mutation of Val(94). Combination of four E-F loop mutations (K92A, A93K, V94A, E97A) in a single mutant reduced the inhibitory potency and binding to levels similar to those seen with NP3 without affecting heme or histamine binding.

Kinetic Changes with Fatigue and Relationship to Injury in Female Runners

This research examined how ground reaction forces (GRF) changed with fatigue induced by an exhaustive treadmill run in female runners. A separate retrospective and prospective analysis correlated initial magnitude of GRF and fatigue-induced changes in GRF with lower-extremity injury. Ninety adult female runners had vertical GRF measured before and after an exhaustive treadmill run. Subjects initially were questioned about previous running injuries, and were contacted during the following year and asked to report any additional running injuries. Fatigue induced by the exhaustive treadmill run resulted in decreased impact peak and loading rates in all runners by an average of 6 and 11%, respectively. The changes in GRF were attributed to altered running cadence, step length, and lower-extremity joint kinematics. It is unclear whether these changes were attempts by the runners to minimize impact forces and protect against injury, or represented a fatigue-induced loss of optimal performance capabilities. An interaction between injury in the previous year and change in impact loading rate with fatigue was observed, suggesting previously injured runners are exposed to relatively higher impact forces over time. Habitual female runners appear to adapt their running style with fatigue, resulting in altered GRF. Changes in GRF with fatigue may be associated with lower-extremity running injuries.

Halophilic biological treatment of tannery soak liquor in a sequencing batch reactor

Hypersaline wastewater (i.e. wastewater containing more than 35 g l −1 total dissolved solids (TDS)) is generated by various industrial activities. This wastewater, rich in both organic matter and TDS, is difficult to treat using conventional biological wastewater treatment processes. Among the industries generating hypersaline effluents, tanneries are prominent in India. In this study, tannery wastewater from soak pit was treated in a lab-scale SBR for the removal of organic matter. The characterisation of the soak liquor showed that this effluent is biodegradable, though not easily, and highly variable, depending on the origin and the nature of the hides. TDS was in the range of 21–57 g l −1 and COD was in the range of 1.5–3.6 g l −1. This soak liquor was biologically treated in an aerobic sequencing batch reactor seeded with halophilic bacteria, and the performance of the system was evaluated under different operating conditions with changes in hydraulic retention time, organic loading rate and salt concentration. The changes in salinity appeared to affect the removal of organic matter more than the changes in hydraulic retention time or organic loading rate. Despite the variations in the characteristics of the soak liquor, the reactor achieved proper removal of organic matter, once the acclimation of the microorganisms was achieved. Optimum removal efficiencies of 95%, 93%, 96% and 92% on COD, PO 4 3−, TKN and SS, respectively, could be reached with 5 days hydraulic retention time (HRT), an organic loading rate (OLR) of 0.6 kg COD m −3 d −1 and 34 g NaCl l −1. The organisms responsible for nitrogen removal appeared to be the most sensitive to the modifications of these parameters.

English

The first large scale, 1,200 gpm capacity, sulfate reducing bioreactor (SRBR) was constructed in 1996 to treat water from an underground lead mine in Missouri. Other large scale SRBR systems have been built elsewhere since then. This technology holds much promise for economically treating heavy metals and has progressed steadily from the laboratory to industrial applications. Scaling-up challenges from bench- and pilot-sized systems include designing for: seasonal temperature variations, minimizing short circuits, changes in metal loading rates, storm water impacts, and resistance to vandalism. However, the biggest challenge may be designing for the progressive biological degradation of the organic substrate and its effects on the hydraulics of the SRBR cells. Due to the wide variability of the organic materials that may be locally available at reasonable costs, the design of organic substrate SRBR systems is not and may never become a cookbook approach. Balancing substrate geochemical requirements with intuitive physical resistance to organic decay currently plays a large role in the large scale system design process.

High‐rate clarification of municipal wastewaters: a brief appraisal

AbstractPilot‐plant studies on the treatment of three wastewaters (biological aerated flooded filter (BAFF) backwash water, post‐primary settling tank effluent and BAFF effluent) have been conducted using a ballasted sedimentation process (ACTIFLO®) coupled with ferric chloride and polyaluminium chloride (PACl) coagulants. The response of the process to shock loads of high solids concentrations was also investigated. Results showed over 80% turbidity, 70% suspended solids, and 50% COD removals to be achievable at rise rates in excess of 80 m h−1 and dose rates of 10–20 mg dm−3 Fe. Slightly improved performance was attained using PACL at half the weight concentration (but about the same molar concentration) as that of Fe. No pH adjustment was necessary and process performance was not significantly influenced by changes in hydraulic loading rate. Effluent quality was largely unaffected by shock organic loads provided coagulant dosing was commensurately increased. Non‐ideal flow through the plant was apparent from the measured residence time, which was ∼25% less than that calculated for plug flow. Clarification data were comparable to those reported for other high‐rate clarification (HRC) processes, with somewhat improved performance in terms of hydraulic retention time and coagulant use. Copyright © 2004 Society of Chemical Industry

Effects of crosshead velocity and sub-zero temperature on mechanical behaviour of hygrothermally conditioned glass fibre reinforced epoxy composites

Abstract Experimental studies have been carried out to study the effects of thermal and moist environments (hygrothermal) on mechanical behaviour of glass fibre/epoxy composites. The hygrothermal conditioning impairs the fibre/matrix interfacial and/or interphasial chemistry, which plays a predominantly important role in determining the mechanical properties, especially the matrix dominated one, of a polymer composite. The hygrothermallly conditioned laminated composites are further treated at −6 °C temperature to freeze the absorbed moisture in the composites. The inter-laminar shear strength (ILSS) is found to be affected by this conditioning and it is also noticed that the further degradation occurs in the frozen state. The present paper also investigates the effect of variation of loading speeds on the degradation behaviour of polymer composites. A change in loading rate may result in variation of failure modes. The lower value of ILSS at lower crosshead speed may be due to higher ductility or failure strain of the epoxy resin.

Muscle activity in the leg is tuned in response to impact force characteristics

Based on results from quasi-static experiments, it has been suggested that the lower extremity muscle activity is adjusted in reaction to impact forces with the goal of minimizing soft-tissue vibrations. It is not known whether a similar muscle tuning occurs during dynamic activities. Thus, the purpose of this study was to determine the effect of changes in the input signal on (a) vibrations of lower extremity soft-tissue packages and (b) EMG activity of related muscles during heel–toe running. Subjects performed heel–toe running in five different shoe conditions. Ground reaction forces were measured with a KISTLER force platform, soft-tissue vibrations were measured with tri-axial accelerometers and muscle activity was measured using surface EMG from the quadriceps, hamstrings, tibialis anterior and triceps surae groups from 10 subjects. By changing both the speed of running and the shoe midsole material the impact force characteristics were changed. There was no effect of changes in the input signal on the soft-tissue peak acceleration following impact. A significant correlation ( R 2=0.819) between the EMG pre-activation intensity and the impact loading rate changes was found for the quadriceps. In addition, the input frequency was shown to approach the vibration frequency of the quadriceps. This evidence supports the proposed paradigm that muscle activity is tuned to impact force characteristics to control the soft-tissue vibrations.

무산소-RBC 공정을 이용한 질소제거 특성 및 동력학적 인자 도출

This study was conducted to investigate anoxic-RBC (rotating biological contactor) and its application in advanced municipal wastewater treatment process to remove biologically organics and ammonia nitrogen. Effluent COD and nitrogen concentration increased as the increase of volumetric loading rate. But, the concentration changes of NO<TEX>$_2$</TEX><TEX>$\^$</TEX>-/ -N and NO<TEX>$_3$</TEX><TEX>$\^$</TEX>-/ -N were little, as compared to COD and NH<TEX>$_4$</TEX><TEX>$\^$</TEX>+/ -N. When the volumetric loading rate increased, COD removal efficiency and nitrification appeared very high as 96.7∼98.8% and 92.5∼98.8%, respectively. However, denitrification rate decreased to 76.2∼88.0%. These results showed that the change of volumetric loading rate affected to the denitrification rate more than COD removal efficiency or nitrification rate. The surface loading rates applied to RBC were 0.13～6.0lg COD/㎡-day and 0.312∼1.677g NH<TEX>$_4$</TEX><TEX>$\^$</TEX>+/-N㎡-day and they were increased as the increase of volumetric loading rate. However, the nitrification rate showed higher than 90%. The thickness of the biofilm in RBC was 0.130 ∼0.141mm and the density of biofilm was 79.62∼83.78mg/㎤. They were increased as surface loading rate increased. From batch kinetic tests, the k<TEX>$\_$</TEX>maxH/ and k<TEX>$\_$</TEX>maxN/ were obtained as 1.586 g C/g VSS-day, and 0.276 g N/g VSS-day, respectively. Kinetic constants of denitrifer in anoxic reactor, Y, k<TEX>$\_$</TEX>e/, K<TEX>$\_$</TEX>s/, and k were 0.678 mg VSS/mg N, 0.0032 day<TEX>$\^$</TEX>-1/, 29.0 mg N/l , and 0.108 day<TEX>$\^$</TEX>-l/, respectively. P and K<TEX>$\_$</TEX>s/, values of nitrification and organics removal in RBC were 0.556 g N/㎡-day and 18.71 g COD/㎡-day, respectively.

Force Measurements of the α5β1 Integrin–Fibronectin Interaction

The interaction of the α 5 β 1 integrin and its ligand, fibronectin (FN), plays a crucial role in the adhesion of cells to the extracellular matrix. An important intrinsic property of the α 5 β 1/FN interaction is the dynamic response of the complex to a pulling force. We have carried out atomic force microscopy measurements of the interaction between α 5 β 1 and a fibronectin fragment derived from the seventh through tenth type III repeats of FN (i.e., FN7-10) containing both the arg-gly-asp (RGD) sequence and the synergy site. Direct force measurements obtained from an experimental system consisting of an α 5 β 1 expressing K562 cell attached to the atomic force microscopy cantilever and FN7-10 adsorbed on a substrate were used to determine the dynamic response of the α 5 β 1/FN7-10 complex to a pulling force. The experiments were carried out over a three-orders-of-magnitude change in loading rate and under conditions that allowed for detection of individual α 5 β 1/FN7-10 interactions. The dynamic rupture force of the α 5 β 1/FN7-10 complex revealed two regimes of loading: a fast loading regime (>10,000 pN/s) and a slow loading regime (<10,000 pN/s) that characterize the inner and outer activation barriers of the complex, respectively. Activation by TS2/16 antibody increased both the frequency of adhesion and elevated the rupture force of the α 5 β 1/wild type FN7-10 complex to higher values in the slow loading regime. In experiments carried out with a FN7-10 RGD deleted mutant, the force measurements revealed that both inner and outer activation barriers were suppressed by the mutation. Mutations to the synergy site of FN, however, suppressed only the outer barrier activation of the complex. For both the RGD and synergy deletions, the frequency of adhesion was less than that of the wild type FN7-10, but was increased by integrin activation. The rupture force of these mutants was only slightly less than that of the wild type, and was not increased by activation. These results suggest that integrin activation involved a cooperative interaction with both the RGD and synergy sites.

Force Spectroscopy of the Leukocyte Function-Associated Antigen-1/Intercellular Adhesion Molecule-1 Interaction

Interactions between leukocyte function-associated antigen-1 (LFA-1) with its cognate ligand, intercellular adhesion molecule-1 (ICAM-1) play a crucial role in leukocyte adhesion. Because the cell and its adhesive components are subject to external perturbation from the surrounding flow of blood, it is important to understand the binding properties of the LFA-1/ICAM-1 interaction in both steady state and in the presence of an external pulling force. Here we report on atomic force microscopy (AFM) measurements of the unbinding of LFA-1 from ICAM-1. The single molecule measurements revealed the energy landscape corresponding to the dissociation of the LFA-1/ICAM-1 complex and provided the basis for defining the energetic determinants of the complex at equilibrium and under the influence of an external force. The AFM force measurements were performed in an experimental system consisting of an LFA-1-expressing T cell hybridoma, 3A9, attached to the end of the AFM cantilever and an apposing surface expressing ICAM-1. In measurements covering three orders of magnitude change in force loading rate, the LFA-1/ICAM-1 force spectrum (i.e., unbinding force versus loading rate) revealed a fast and a slow loading regime that characterized a steep inner activation barrier and a wide outer activation barrier, respectively. The addition of Mg 2+, a cofactor that stabilizes the LFA-1/ICAM-1 interaction, elevated the unbinding force of the complex in the slow loading regime. In contrast, the presence of EDTA suppressed the inner barrier of the LFA-1/ICAM-1 complex. These results suggest that the equilibrium dissociation constant of the LFA-1/ICAM-1 interaction is regulated by the energetics of the outer activation barrier of the complex, while the ability of the complex to resist a pulling force is determined by the divalent cation-dependent inner activation barrier.

Damköhler number distributions and constituent removal in treatment wetlands

Using hypothetical wetland simulations and data from the literature, Kadlec [Eco. Eng. 15 (2000) 105] recently demonstrated that plug-flow models commonly used to quantify treatment wetland performance fail to describe conditions other than those under which calibration data are collected. Parameters of these models (removal rate constants ( k) and background concentrations ( C*)) demonstrate apparent dependence on inlet concentration and hydraulic loading rate which is not alleviated by including dispersion to address non-ideal flow. The phenomenon can be understood as resulting from an interdependence between k and local flow velocity, due to the functional dependence of each on drag-inducing surfaces (and attached biofilms) associated with submerged vegetation and litter. This paper presents a simple method, based on theoretical considerations, for determining C* using inlet–outlet data, independent of the degree of mixing or the nature of the removal processes. This paper also expands upon the hypothetical multi-channel example to suggest a modeling approach in which a wetland is treated conceptually as an ensemble of parallel, non-interacting stream tubes in plug-flow, characterized by a continuous distribution of Damköhler numbers. The Damköhler number distribution (DND) can be estimated from the residence time distribution (RTD) under the assumption of uniform flow path length. For such a wetland, under steady state conditions and with constant inlet concentration, the fraction of a removable pollutant remaining as a function of normalized distance from inlet to outlet is given by the Laplace transform of the DND. Similarly, the DND can be derived from the inverse Laplace transform of the normalized concentration versus normalized distance curve. Given both an RTD and a DND, it is possible to investigate the relationship between k and residence time, and the mechanistic nature of the removal process. Employing these concepts makes it possible to generate an expression for normalized concentration as a function of fractional distance that is unaffected by changes in inlet concentration, and inherently takes into account changes in hydraulic loading rate.

A new model for anaerobic processes of up-flow anaerobic sludge blanket reactors based on cellular automata

The advantageous performance of the UASB reactors is due to the immobilisation of the active biomass, since bacteria coagulate forming aggregates usually called granules. Changes in organic loading rate, hydraulic loading rate or influent substrate composition usually result in changes in granule characteristics and lead to different reactor behaviour. A dynamic mathematical model has been developed for the anaerobic digestion of a glucose based synthetic wastewater in UASB reactors. Cellular automata (CA) theory has been applied to simulate the granule development process. The model takes into consideration that granule diameter and granule microbial composition are functions of the reactor operational parameters and is capable of predicting the UASB performance and the layer structure of the granules.

Age-related changes in venticular-arterial coupling: pathophysiologic implications.

The interaction of the heart with the systemic vasculature, termed ventricular-arterial coupling, is a central determinant of net cardiovascular performance. The capacity of the body to augment cardiac output, regulate systemic blood pressure, and respond appropriately to elevations in heart rate and venous filling volume is related as much to the properties of the heart as it is the vasculature into which the heart ejects. With aging, changes in the arterial system associated with vascular stiffening and a reduction in peripheral vasomotor regulation can profoundly affect this coupling by imposing far greater pulsatile and late-systolic loads on the heart. This is accompanied by tandem increases in left ventricular end-systolic stiffness (end-systolic chamber elastance) and reduced diastolic compliance. Altered coupling related to combined ventricular-vascular stiffening increases blood pressure lability for a given change in hemodynamic loading and heart rate (i.e. under stress demands), as well as reduces the capacity to enhance cardiac output without greatly increasing cardiac wall stress. Furthermore, such coupling influences myocardial perfusion by elevating the proportion of coronary flow during the systolic time period. This more closely links ventricular systolic function with myocardial flow, and can compromise flow reserve and exacerbate ischemic dysfunction when ventricular systolic function declines, such as with concomitant heart failure or acute regional ischemia. This article reviews the theory behind ventricular-arterial coupling analysis, the changes in coupling that occur with age and their impact on normal reserve mechanisms, and the likely role of these changes have on heart failure and ischemic heart disease and disease therapy in the elderly.

応力ステップ・応力速度変化に伴う地震発生率の変化 地震発生確率予測の高精度化に向けて

Traditionally, long-term earthquake probability has been estimated using regional seismicity or a characteristic earthquake hypothesis without considering any recent stress perturbations caused by sudden crustal deformation or nearby earthquakes. The conventional calculation method ignores such processes observed time dependent clustering of earthquakes, and the occurrence of aftershocks or anti-shocks (seismicity rate decreases). I have thus introduced a method to seek the time-dependent seismicity rate based on stress interaction, incorporating the rate-and state-dependent friction law. Regarding earthquake productivity response to the stress state, coseismic stress step controls amplification of seismicity rate increase. In addition, assuming that the constitutive parameter and normal stress are constant throughout time, the aftershock or anti-shock duration is inversely proportional to the regional tectonic stressing rate. Thus, influence of the stress step lasts longer where the loading rate is slow, and the long-term probability retains the stress-related change longer. In addition, change in the loading rate proportionally causes the change in the earthquake productivity, in other words earthquake probability, with some delay estimated by a new loading rate. The response time to the sudden loading rate change depends on a new loading rate as predicted by the rate-and state-friction theory.To make further validations about this theory and method, I have investigated two cases of stress triggering, 2000 seismic swarm activity in and around the Izu Islands, and the October 6, 2000, M7.3 Tottori-ken-seibu earthquake. In the Izu swarm activity, the factor of the stressing rate changes was focused. Observed hundreds-to thousands-fold increases of seismicity rate than usual during the active two-month period are almost equivalent to the increases in the tectonic stressing rate caused by a dike intrusion. In contrast, long aftershock duration and long influence of the stress perturbation associated with a low stressing rate were tested in the Tottori case. Even though we need to incorporate additional factors such as viscoelastic behavior and change in earthquake size distribution, this method is expected to contribute more precise long-term earthquake probabilistic forecasting together with welldetermined data from recent GPS and seismic networks.

Response of RC Beams Strengthened with CFRP Laminates and Subjected to a High Rate of Loading

Results are presented of an experimental program undertaken to investigate the effects of strain rate on the behavior of reinforced concrete (RC) beams strengthened with carbon fiber-reinforced polymer (CFRP) laminates. Nine 3-m RC concrete beams, one unstrengthened, four strengthened with S-type CFRP laminates, and four strengthened with R-type laminates, were loaded under four different loading schedules. The stroke rates ranged from 0.0167 mm/s (slow rate of loading) to 36 mm/s (fast rate of loading). This induced a strain rate in the CFRP of 2.96 με/s (slow rate) to 6,930 με/s (fast rate). Some beams were subjected to either 1 or 12 cycles of loading prior to a fast rate of loading to failure. The rapidly loaded beams showed an increase of approximately 5% in capacity, stiffness, and energy absorption. Ductility and the mode of failure were not directly affected by the change in loading rate. Precycled beams performed similarly to the beams loaded monotonically to failure but showed a 10% increase in service stiffness and a 10% loss in energy absorption. A finite-element, layered analysis is presented to predict the moment-curvature response of CFRP strengthened RC beams. The model includes the effects of strain rate and correlates well with the experimental data.

Temperature and Loading Rate Effects on the Fracture Behaviour of Adhesively Bonded GFRP Nylon-6,6

The combined effect of varying test temperature and loading rate on the Mode II fracture toughness of plasma-treated GFRP Nylon-6,6 composites bonded using a silica-reinforced epoxy adhesive has been studied. End notch flexure tests have shown that the adhesive system used in this study offers a wide range of fracture energies that are extremely sensitive to changes in temperature and loading rate. Increasing the test temperature resulted in a substantial reduction in the Mode II fracture toughness of the adhesive, with the value of GIIc at 60°C being approximately one-half of the room temperature value. In contrast, increasing the crosshead displacement rate at a given temperature has been shown to increase the value of GIIc by up to 250%. Compression tests performed on bulk adhesive specimens revealed similar trends in the value of [sgrave]y with temperature and loading rate. In addition, it was found that the plasma treatment employed in this study resulted in stable crack propagation through the adhesive layer under all testing conditions. A more detailed understanding of the effect of varying temperature and loading rate on the failure mechanisms occurring at the crack tip was achieved using the double end notch flexure (DENF) geometry, which was considered in tandem with the fracture surface morphologies. Here, changes in the degree of matrix shear yielding and particle-matrix debonding were used to explain the trends in [sgrave]y and GIIc.