Function Of Time Research Articles

An Analytical Model to Evaluate the Static Soil Pressure Throughout Geological Era

In this study, the time dependent characteristics of the soil pressure coefficient is theoretically investigated and a new model is developed to evaluate the static soil pressure in a normally consolidated soil deposit during geological era. The volumetric deformation of soil is described by the Kelvin model, while its shear deformation is represented by the modified Maxwell model assuming the shear- creep relationship as a linear function of the time logarithm. By employing the “elastic-viscoelastic correspondence principle”, the coefficient of soil pressure is found as a function of time, indicating an increase within the geological time span

Mutual Inhibition, Competition, and Periodicity in a Two Species Chemostat-like System

A model addressing mutual inhibition in a peiodic chemostat is presented in this paper. The operating parameters, including the nutirent uptake function, washout rate, and nutrient concentration are allowed to be periodic functions of time, with comensurate periods. It is shown that with mutual inhibition, competitive exclusion always holds in models that would allow coexistence without inhibition. We further show that initial conditions play a crucial role in determining which species survives. Simulations using MATLAB appear to confirm the predictions of the models. Some results from the simulations are presented graphically.

Formal Verification of Logic Control Systems with Nondeterministic Behaviors

This paper describes a formal modeling and verification of an arm pick-and-place system, in which nondeterministic behaviors of the arm state condition and timer function blocks are applied. We design an appropriate PLC program using a ladder diagram (LD) for the arm pick-and-place operation and apply in it a situation where the arm may drop the product or material being gripped because of an external force. In addition, the timer function blocks are used with formalization of their finite-state logical properties. We use an actual model of the arm to verify that safe operations are established for normal product pick-and-place, as well as when the product has fallen. In addition, we perform arm model verifications for five important temporal properties using the NuSMV model checker. We present two types of experiments to validate the safety of the designed LD program. We also verify that the nondeterminism that appears as a result of the system behaviors can be formalized and used to represent logical assumptions for the properties that need to be verified.

Inverse determination of unsteady temperatures and heat fluxes on inaccessible boundaries

Abstract. The direct measurement of temperatures and heat fluxes may be difficult or impossible on boundaries that are inaccessible, such as internal cavities, or exposed to harsh environmental conditions that would destroy the thermal sensors. In such circumstances, one may inversely determine the temperature and heat fluxes on these unknown boundaries by using over-specified conditions on boundaries where such information can be readily collected. This assumes the geometry and material properties of the domain are known. Algorithms for solving these problems, such as those based on finite difference, finite element, and boundary element, are well known for the case where measured boundary conditions are not a function of time. In this work, we demonstrate an inverse finite element method that effectively solves this inverse heat conduction problem using over-specified temperatures and heat fluxes that are time varying. The material properties may be highly heterogeneous and non-linear. A boundary regularization method is used to stabilize the method for cases involving errors in temperature and heat flux measurements. Several three-dimensional examples are given using simulated measurements with and without measurement errors, to demonstrate the accuracy of the method.

Butanol Production from Lignocellulosic-based Hexoses and Pentoses by Fermentation of Clostridium Acetobutylicum

The Acetone-Butanol-Ethanol (ABE) fermentation is receiving renewed interest as a way to upgrade renewable resources into valuable base chemicals and liquid fuels. Abundance and un-competitiveness with food sources are desired features of a potential substrate, and they are met by lignocellulosic biomass.This contribution is about the characterization of the ABE fermentation by C. acetobutylicum DSM 792 using sugars representative for hydrolysis products of lignocellulosic biomass: hexoses (glucose and mannose) and pentoses (arabinose and xylose).Batch fermentations of single sugars were carried out. The conversion process was characterized as a function of time in terms of biomass, acids and solvents concentrations as well as pH and total organic compounds. C. acetobutylicum was able to convert all investigated sugars. The conversion into solvents was strongly enhanced by the presence of CaCO3 in the fermentation medium.

Prediction of project cash flow using time-depended evolutionary LS-SVM inference model

Purpose The ability to predict cash demand is crucial for the operation of construction companies. Reliable cash flow prediction during the execution phase can help managers to avoid cash shortages and to control project cash flow effectively. Method This paper presents a new inference model, CF-ELSIMT, for cash flow forecasting. The developed CF-ELSIMT utilizes weighted Least Squares Support Vector Machine (wLSSVM) as a supervised learning technique to generalize the mapping function between input and output of cash flow time series. A novel dynamic time function (TF) is employed to determine the weighting values associated with data in different time periods. The dynamic TF allows the model to deal with distinct characteristics in cash flow time series. To optimize the model’s tuning parameters, the new inference model incorporates Differential Evolution (DE) as the search engine. In addition, a machine-learning-based interval estimation (MLIE) approach is used to arrive at the prediction interval of forecasted cash demand. Results & Discussion The CFELSIMT provides construction planners with a point estimate coupled with the lower and upper prediction intervals. Experimental results and comparisons have demonstrated that the newly established model has enhanced the forecasting accuracy.

Optimal Replenishment Policy for an Inventory Model with Demand Follows Innovation Diffusion Process under Permissible Delay in Payments

In this paper a mathematical model has been developed for obtaining the Economic Order Quantity (EOQ) in which the interaction of EOQ with marketing parameters such as external and internal influences under the condition of permissible delay in payments have been considered. The model assumes that the demand is a function of time follows from the adoption behaviour of Bass's diffusion model [5]. The two different cases of permissible delay in payments have been discussed to know the condition of economic ordering policies in a different situation of credit period offered. The integrated effect of both the factors that is permissible delay in payments as well as the marketing parameters on the economic ordering policies of the products has been considered. A solution procedure is developed to find the optimal order quantity and replenishment time, which minimizes the total cost of an inventory system. A numerical example followed by sensitivity analysis of the optimal solution with respect to different parameters of the system has been performed to illustrate the effectiveness of the model.

Single-Input/Single-Output Adaptive Flutter Suppression of a Three-Dimensional Aeroelastic System

Nomenclature  = estimated system matrix As0 = time invariant generalized aerodynamic stiffness matrix of the structural modes, As0 2 R 4 As1 = time invariant generalized aerodynamic damping matrix of the structural modes, As1 2 R 4 As2 = time invariant generalized aerodynamic mass matrix of the structural modes, As2 2 R 4 b = semichord of the wing, m B = estimated input matrix of control B = diagonal matrix of modal damping Ĉ = estimated output matrix of system D = matrix used in minimum-state rational function approximation e1 = estimated prediction error P t = gain matrix P s = estimated denominator polynomial of the transfer function of the controlled aeroelastic system K = stiffness matrix of elastic modes, diagonal for orthogonal elastic modes M = modal mass matrix involving elastic modes only, diagonal due to the orthogonality of elastic modes M = inertial coupling submatrix between control modes and elastic modes Qm s = transfer function of the reference model qd = dynamic pressure, Pa u = control input, rad V = flight speed, m=s v = measurement noise w = Gaussian random input to turbulence in spectral form x t = state vector of the aeroelastic system, including the first four modal displacements , modal velocities _ , aerodynamic state vector and actuator state vector Xa = aerodynamic state vector ym t = reference output signal, m=s Ẑ s = estimated numerator polynomial of the transfer function of the controlled aeroelastic system = generic individual control surface deflection as a function of time, 2 R, rad p = vector of the unknown parameters, p 2 R p = estimation of p = vector of the generalized modes, 2 R

HEARING ASSISTANCE SYSTEM INCLUDING DATA LOGGING CAPABILITY AND METHOD OF OPERATING THE SAME

The invention relates to a method of operating a system for providing hearing assistance to a user (101), comprising: capturing and processing audio signals by a transmission unit (102) and transmitting the audio signals from the transmission unit (102) via a wireless audio link to a receiver unit (103); processing the received audio signals in the receiver unit (103); stimulating the user's hearing, by stimulating means (38, 136) worn at or in the user's ear, according to the audio signals from the receiver unit (103); logging data by recording the values of at least one operation parameter of the transmission unit (102) and/or the receiver unit (103) as a function of time and/or by recording data derived from the values of at least one operation parameter of the transmission unit (102) and/or the receiver unit (103) as a function of time in the transmission unit (102); and reading the logged data from the transmission unit (102).

‘Of Clocks and Calendars’

‘Of Clocks and Calendars’

TIME DEPENDENT THERAPY BASED ON CHRONOPHARMACOLOGY

Chronopharmacology is useful to solve problems of drug optimization, i.e. to enhance the desired efficiency or to reduce its undesired effects. In the human organism (among other animal species) the metabolic fate of a pharmacologic agent (as well as that of a nutrient) is not constant as a function of time. Thus, the chronobiologic approach of pharmacologic phenomena involves a lesser risk of errors and/or false information than the conventional homeostatic approach. This review focuses on chronopharmacotherapy of various diseases related to different human body systems, and also provides a molecular biological explanation for the influence of medications on the clock genes. Biological rhythms not only impact the pathophysiology of diseases, but the pharmacokinetics and pharmacodynamics of medications. Chronopharmacotherapy is the investigative science that elucidates the biological rhythm dependencies of medications

Modelo de desnutrición animal para la evaluación de estudios de farmacocinética

Background: Protein energy malnutrition is a public health problem affecting a great number of people. Pathophysiological imbalances in malnourished individuals have a profound impact on drug pharmacokinetics. Objective: To develop an animal model of undernutrition using male Wistar rats to be used to assess, in further studies, the impact of nutritional status on the oral bioavailability and pharmacokinetics of drugs. Desing: Animals were randomly assigned to one of two groups and fed different diets for 26 days: WN (well-nourished/ regular diet, N = 61) and UN (under-nourished/protein- calorie restricted diet, N = 72). Assessment of the animals’ nutritional status was performed taking into account serum albumin, total cholesterol level and total body weight. A kinetic model incorporating population kinetic analysis (NONMEM) was developed to analyze body weight versus time profiles in the adaptation period following administration of the two aforementioned diets. Results: Serum albumin plasma levels were lower than 2.3 g/dL in 80% (60/72) of malnourished animals at the end of the adaptation period. The range of the total serum cholesterol was similar in both groups at the end of the adaptation period. Total body weight in all cases was less than 230 g for malnourished animals and higher than 240 g for well-nourished animals. The kinetic model assayed was confirmed to be an expansion module characterized by linear weight gain and a decline module characterized by exponential weight loss, where the weight loss rate constant is an exponential function of time. The bootstrap resampling method confirmed the stability of the model eventually selected. Conclusions: The animal model developed in this study is reliable and could be of use in evaluating the impact of nutritional state on the pharmacokinetics of drugs. The proposed mathematical model allows the body weight of animals to be predicted at a given time taking into account the diet followed in the experimental period.

Determination of temperature effect on mechanical properties of templated mesoporous silica aerogels by nanoindentation method

Cross-linking is known as a chemical process to improve the mechanical properties by adding polymer. Therefore, the pore walls of aerogels can be strengthened by coating with polymer. In this study, the mechanical properties of a cross-linked monolithic silica aerogel have been examined by nanoindentation tests at different temperatures. Creep compliance values were analyzed as a function of time by linear viscoelastic equations using the test data of nanoindentation. It is determined that the creep compliance values obtained from nanoindentation are much higher than that of compressive test. Additionally, from the relaxation modulus curves, it can be expressed that the aerogel sample used retains its general long-term viscoelastic behavior at elevated temperatures. Key words: Silica aerogel, nanoindentation, creep behavior, temperature test, linear viscoelasticity, depth-sensing indentation.

Potencial de ação: do estímulo à adaptação neural

INTRODUÇÃO: O potencial de ação (PA) origina-se graças a uma perturbação do estado de repouso da membrana celular, com consequente fluxo de íons, por meio da membrana e alteração da concentração iônica nos meios intra e extracelular. OBJETIVOS: Sintetizar o conhecimento científico acumulado até o presente sobre o potencial de ação neural e o seu processo de adaptação sob aplicação de um estímulo constante. MATERIAIS E MÉTODOS: Busca realizada nas bases Springer, ScienceDirect, PubMed, IEEE Xplore, Google Acadêmico, Portal de Periódicos da Capes, além de livros referentes ao assunto. O idioma de preferência selecionado foi o inglês, com as keywords: action potential; adaptation; accommodation; rheobase; chronaxy; nerve impulse. Efetuou-se a procura de artigos com uma janela de tempo de 1931 a 2010 e livros de 1791 a 2007. RESULTADOS: Dos trabalhos selecionados, foram extraídas informações a respeito dos seguintes tópicos: potencial de ação e suas fases; condução nervosa; reobase; cronaxia; acomodação; e adaptação neuronal. CONCLUSÃO: Um estímulo que crie PA, se aplicado de maneira constante, pode reduzir a frequência de despolarizações em função do tempo e, consequentemente, adaptar a célula. O tempo que a célula demora, na ausência de estímulos, para recuperar sua frequência original é definido como desadaptação.

Spatial fluctuations in transient creep deformation

We study the spatial fluctuations of transient creep deformation of materials as a functionof time, both by digital image correlation (DIC) measurements of paper samples and bynumerical simulations of a crystal plasticity or discrete dislocation dynamics model. Thismodel has a jamming or yielding phase transition, around which power law or Andradecreep is found. During primary creep, the relative strength of the strain rate fluctuationsincreases with time in both cases—the spatially averaged creep rate obeys the Andrade lawϵt ∼ t − 0.7, while the time dependence of the spatial fluctuations of the local creep rates is given byΔϵt ∼ t − 0.5. A similar scaling for the fluctuations is found in the logarithmic creep regime that istypically observed for lower applied stresses. We review briefly some classical theories ofAndrade creep from the point of view of such spatial fluctuations. We consider thesephenomenological, time-dependent creep laws in terms of a description based on anon-equilibrium phase transition separating evolving and frozen states of the systemwhen the externally applied load is varied. Such an interpretation is discussedfurther by the data collapse of the local deformations in the spirit of absorbingstate/depinning phase transitions, as well as deformation–deformation correlations andthe width of the cumulative strain distributions. The results are also comparedwith the order parameter fluctuations observed close to the depinning transitionof the 2d linear interface model or the quenched Edwards–Wilkinson equation.

Utilization of Solar Energy and Atmospheric Oxygen in the Photodregradation of Diesel in Water by Cu/TiO2 Catalysts

AbstractPhotocatalytic destruction of the water soluble diesel fraction (WSF) was performed using Cu/TiO2 catalysts. Inexpensive and clean solar light and atmospheric oxygen were used as the energy source and oxidant, respectively. We investigated the effect of Cu species on the formation of a doping energy level between the conduction and valence band in TiO2. Photocatalytic reactions were investigated by monitoring the evolution of WSF as a function oftime of solar irradiation by UV-vis and FTIR spectroscopic techniques. The photocatalytic process in the presence of 5%Cu/TiO2 catalyst, is shown to be quantitatively efficient in the destruction of the water-soluble diesel fraction. The total destruction of water-soluble compounds originating from diesel residues indicates that photocatalysis can be employed for WSF treatment.

Implementasi Sensor Pyroelectric Infra Red (PIR) Sebagai Pewaktu Televisi

Energy dissipation is very disturbing for a country's survival, including Indonesia. Power dissipation generally occurs because of the lifestyle of people who tend consumptive Indonesia. One example of energy waste in the household is often forgot to turn off the television. The timer on the television was made in order to be able to set how long the TV will die (off) by itself in accordance with a prearranged time. However, not everyone can or know of this timer function, especially those who have elderly. Many cases of elderly people see television to fall asleep without turning it off. In this case certainly happens waste of electricity. In this study will be designing and manufacturing tools that can be used as a detector of movement of people in front of the television, so television is only lights up if there is a movement of people who watch television. From the results of this research tool is able to detect the movement of people in front of the television, with the effective distance of the tool is 2 meters.

Separating the spindle, checkpoint, and timer functions of BubR1

BubR1 performs several roles during mitosis, affecting the spindle assembly checkpoint (SAC), mitotic timing, and spindle function, but the interdependence of these functions is unclear. We have analyzed in Drosophila melanogaster the mitotic phenotypes of kinase-dead (KD) BubR1 and BubR1 lacking the N-terminal KEN box. bubR1-KD individuals have a robust SAC but abnormal spindles with thin kinetochore fibers, suggesting that the kinase activity modulates microtubule capture and/or dynamics but is relatively dispensable for SAC function. In contrast, bubR1-KEN flies have normal spindles but no SAC. Nevertheless, mitotic timing is normal as long as Mad2 is present. Thus, the SAC, timer, and spindle functions of BubR1 are substantially separable. Timing is shorter in bubR1-KEN mad2 double mutants, yet in these flies, lacking both critical SAC components, chromosomes still segregate accurately, reconfirming that in Drosophila, reliable mitosis does not need the SAC.

Variação espaço-temporal dos parâmetros para a modelagem estocástica da precipitação pluvial diária no Rio Grande do Sul

O Rio Grande do Sul é um dos maiores produtores de grãos do Brasil, sendo a maioria das culturas conduzida em sistemas não irrigados, tornando-lhes extremamente dependentes das condições climáticas e do regime pluviométrico. Tal fato inspira diversas pesquisas na tentativa de caracterizar o comportamento espacial e temporal das precipitações. Dessa forma, o objetivo do presente trabalho foi estudar a variação espacial e temporal dos parâmetros alfa e beta da função gama para a geração de dados de precipitação pluvial diária no Estado. Os dados de precipitação pluviométrica foram obtidos junto à ANA - Agência Nacional de Águas. A modelagem da precipitação diária foi dividida em ocorrência e quantidade. Realizou-se a estimativa dos parâmetros alfa e beta da função gama a partir das séries históricas, seguida do ajuste desses parâmetros em função do tempo e do espaço e posterior comparação entre os valores estimados e os observados. De acordo com os resultados obtidos, conclui-se que a metodologia desenvolvida pode ser aplicada para a geração de séries sintéticas de precipitação pluvial diária nas diferentes estações pluviométricas do Rio Grande do Sul.

Experiences with the electronic spermcounter in andrologic routine work.

Evaluation of semen samples is a time consuming process, which can be facilitated significantly by means of the electronic spermcounter. The device represents a microcomputer system operating with three main functions: Counter function, morphologic function and timer function. In order to quantify the advantages of the electronic apparatus it was compared with a mechanical handheld counter and a mechanical blood-cell counter. Determinations of sperm density and morphologic analysis of stained specimen consumed significantly less time when the sperm counter was used. The advantages of the timer function, while apparent, could not be quantitated and expressed in numbers. The electronic spermcounter makes microscopic evaluations of semen samples faster, easier and more reliable. Thus the device is useful for those dealing routinely with numerous spermiograms, i.e. andrologists, veterinarians and other working in the field of reproduction.