A study of the local site effects on the ground response for the city of Eskişehir,Turkey

Bulletin of Engineering Geology and the Environment - Local soil characteristics play a key role in determining soil-structure interaction and reliability of the superstructure behavior under...     

Properties of Carbopol Solutions as Models for Yield-Stress Fluids

ABSTRACT: The effect of pH on the non-Newtonian viscosity (η)of aqueous Carbopol 940 solutions is presented with high resolution (pH increments about 0.4) between pH = 2.8 and 12.7. Aqueous NaOH was used to adjust pH of 1.48 wt % Carbopol solutions. A Contraves viscometer was used to measure steady-flow shear stress at known shear rate (γ) over the range γ= 8 to 195 s⁻¹. Yield stresses and shear-thinning η(γ) were observed. Data were fitted with a Herschel-Bulkley model, whose parameters (including yield stress) were expressed as functions of pH. Comparisons were made of η(γ) to the dynamic viscometric properties η'(ω) and η*(ω) for comparable ranges of γ and frequency (ω): A fairly close match was found between η and η* but η«η'. pH dependence included previously unreported extrema of h(pH) in the range of pH = 6.2 to 6.6. Because of sensitive control of rheological properties with pH, Carbopol solutions can be used to mimic a great range of shear-thinning and yield-stress behavior that should make them useful for model studies directed toward process and equipment design and evaluation.     

An interdisciplinary heuristic evaluation method for universal building design

This study highlights how heuristic evaluation as a usability evaluation method can feed into current building design practice to conform to universal design principles. It provides a definition of universal usability that is applicable to an architectural design context. It takes the seven universal design principles as a set of heuristics and applies an iterative sequence of heuristic evaluation in a shopping mall, aiming to achieve a cost-effective evaluation process. The evaluation was composed of three consecutive sessions. First, five evaluators from different professions were interviewed regarding the construction drawings in terms of universal design principles. Then, each evaluator was asked to perform the predefined task scenarios. In subsequent interviews, the evaluators were asked to re-analyze the construction drawings. The results showed that heuristic evaluation could successfully integrate universal usability into current building design practice in two ways: (i) it promoted an iterative evaluation process combined with multi-sessions rather than relying on one evaluator and on one evaluation session to find the maximum number of usability problems, and (ii) it highlighted the necessity of an interdisciplinary ad hoc committee regarding the heuristic abilities of each profession. A multi-session and interdisciplinary heuristic evaluation method can save both the project budget and the required time, while ensuring a reduced error rate for the universal usage of the built environments.     

Removal of acetic acid from water by catalytic distillation. Part 2: Modeling and simulation studies

A simulation program has been established by incorporating basic models for reaction kinetics, vapor–liquid equilibrium and mass transfer into Aspen Plus (Aspen Technology Inc., 1996) to simulate the catalytic distillation process for the removal of dilute acetic acid from water. The simulated concentration profiles agree well with those measured under various operating conditions.     

Online composition estimation and experiment validation of distillation processes with switching dynamics

This study explores both the theoretical and experimental investigations of applying a continuum and noncontinuum state estimator to composition estimation in a distillation process with switching dynamics. In a hybrid distillation modeling, the column compositions are considered as continuum states while the operating modes are modeled as noncontinuum states. A moving horizon estimator (MHE), which has the capability to handle process constraints is developed for composition estimation in a distillation process under known switching mode criteria using the available temperature measurements. The performance of a MHE is shown to be better than that of EKF in handling process and measurement noise under switching dynamics. For some situations where the system operating mode transition is unknown, a new approach to state estimation under unknown switching functions is investigated. The proposed method combines a MHE for composition estimation with a mode change detector to detect a change in the system operating mode and an operating mode estimator to identify the functioning mode. In the presence of both the measurement noise and plant-model mismatch, the developed estimator is shown to be effective in estimating both the column composition and the system operating mode accurately.     

Numerical modelling and characterization of nanofiltration membranes for the separation of carbohydrate mixtures

The results of an experimental and computational investigation of the selective separation of carbohydrates on nano‐membranes in cross‐flow filtration are reported. Two commercial membranes (NF270‐400 and TFC‐SR3) were characterised in terms of permeability and rejection of carbohydrate solutions. It is shown that the membranes can be used to recover glucose and galactose from their mixtures with lactose. The permeate flux is shown to depend on sugar concentration, with permeate flux decreasing as the concentration increases. Quantitative evaluation using numerical analysis of the above flow and separation process showed that the performance of nano‐membranes can be captured and reproduced with sufficient accuracy, thereby reducing the number of experiments require to evaluate the suitability of membranes in different applications. A Fickian approach is adopted to model the separation, and is shown to be effective.     

Risk factors for Kaposi's sarcoma in HIV-positive subjects in Uganda

BACKGROUND: Kaposi's sarcoma (KS) is associated epidemiologically with HIV infection and with human herpesvirus 8 (HHV-8 or KSHV). Both KS and HIV infection are common in Uganda. We conducted a case-control study of 458 HIV-seropositive. Ugandan adults with KS and 568 HIV-seropositive subjects without KS to examine risk factors for HIV-associated KS. METHODS: We recruited newly diagnosed adult KS cases from five hospitals in Kampala, Uganda and controls from a large referral clinic for HIV infection at Mulago Hospital. All cases and controls were counselled and tested for HIV and answered an interviewer-administered questionnaire about their home, socio-economic conditions, lifestyle and sexual behaviour before they became ill. Only HIV-seropositive subjects were included in the analysis. RESULTS: There were 295 males and 163 females with KS and 227 male and 341 female controls. Age distribution was similar but there was a higher proportion of cases (45%) than controls (29%) residing in rural regions of Uganda. KS cases were more likely than controls to have a higher level of education (X2 for trend, 4.8; P = 0.03), to have occupations associated with affluence [chi 2 for heterogeneity, 17.3 on 5 degrees of freedom (df); P = 0.004] and to come from larger settlements [adjusted odds ratio (OR) for settlements of > 1000 versus 10-99 houses, 1.8; 95% confidence interval (CI), 1.1-3.0]. Cases were more likely than controls to have high household income (chi 2 for trend, 32.6; P < 0.001) and other markers of urban or rural wealth such as owning several cows (chi 2 for trend, 9.5; P = 0.002). Cases were more likely to travel away from home (adjusted OR, 1.6; 95% CI, 1.1-2.3) and more likely to have spent increasing time in contact with water (chi 2 for trend, 12.3; P < 0.001). Few indices of sexual behaviour were related to risk of KS, including reported number of sexual partners. Cases were more likely than controls to be married to one rather than several spouses (adjusted OR, 1.6; 95% CI, 1.2-2.2) and to have reported a history of sexually transmitted diseases (STD) (adjusted OR, 1.6; 95% CI, 1.2-2.3). CONCLUSIONS: Among HIV-infected subjects, KS cases are characterized by better education and greater affluence, compared with controls. Urban address, travel away from home, exposure to water, monogamous marriage and self-reported STD were also more frequent among KS cases than controls. The higher socio-economic status of persons with HIV and KS may be a marker for enhanced exposure to a possibly sexually transmitted agent, or for a delayed exposure to a childhood infection. The risk posed by exposure to water among KS cases requires further study.