Logarithmic Difference Research Articles

An New Image Feature Based on ROLD

To make robot more intelligence, this paper proposed a new image feature named as ROLD-map which based on Rank-Ordered Logarithmic Difference (ROLD), and this feature enable researchers understand images complication directly and accuracy. Experimental data show that it can recognize the sky, tree and road obviously with very little time through proposed feature. It provides the fundamental analysis for improving the precision of image recognition, and also gives the reference research for improving the precision of image recognition for the process of visual navigation of robot.

English

  The rise in gross incomes and the decline in poverty in rural areas are considered evidence of economic restructuring and technological development efforts in last three decades in the United States. However, these positive effects of transformations in rural areas still do not match the rate of economic growth enjoyed by urban areas. This paper examined income convergence in 875 counties of the 10-state southeastern region using Census data for 1980 and 2000. Logarithmic difference of average per capita income between those years was regressed on socioeconomic variables using Ordinary Least Square (OLS) model. The study found important roles of human capital development and employment growth in income convergence and variations in income growth in places that differ in demographic attributes, job opportunities, geography, and resource concentrations. The study provided important insights to rural policy makers to formulate place-based economic development strategies which are practical and realistic to address economic development in the most impoverished rural places in the southeastern United States.   Key words: Agglomeration, census, clusters, convergence, industries, employment, income, southeastern.

Stochastic nature of series of waiting times

Although fluctuations in the waiting time series have been studied for a long time, some important issues such as its long-range memory and its stochastic features in the presence of nonstationarity have so far remained unstudied. Here we find that the "waiting times" series for a given increment level have long-range correlations with Hurst exponents belonging to the interval 1/2<H<1. We also study positive-negative level asymmetry of the waiting time distribution. We find that the logarithmic difference of waiting times series has a short-range correlation, and then we study its stochastic nature using the Markovian method and determine the corresponding Kramers-Moyal coefficients. As an example, we analyze the velocity fluctuations in high Reynolds number turbulence and determine the level dependence of Markov time scales, as well as the drift and diffusion coefficients. We show that the waiting time distributions exhibit power law tails, and we were able to model the distribution with a continuous time random walk.

Dynamic range in a neuron network with electrical and chemical synapses

The dynamic range is the logarithmic difference between maximum and minimum levels of sensation produced by known stimuli. In the human sensory systems the dynamic ranges are typically larger than for single neurons, this amplification being essentially a collective effect of the neural network. We investigated the dynamic range exhibited by a cellular automaton network with electrical and chemical synapses, when the stimuli are modelled by a Poisson process of suprathreshold events of stereotyped unit amplitude and the neuron response is its average firing rate.

Statistical considerations in bioequivalence of two area under the concentration–time curves obtained from serial sampling data

In this paper, we study the bioequivalence (BE) inference problem motivated by pharmacokinetic data that were collected using the serial sampling technique. In serial sampling designs, subjects are independently assigned to one of the two drugs; each subject can be sampled only once, and data are collected at K distinct timepoints from multiple subjects. We consider design and hypothesis testing for the parameter of interest: the area under the concentration–time curve (AUC). Decision rules in demonstrating BE were established using an equivalence test for either the ratio or logarithmic difference of two AUCs. The proposed t-test can deal with cases where two AUCs have unequal variances. To control for the type I error rate, the involved degrees-of-freedom were adjusted using Satterthwaite's approximation. A power formula was derived to allow the determination of necessary sample sizes. Simulation results show that, when the two AUCs have unequal variances, the type I error rate is better controlled by the proposed method compared with a method that only handles equal variances. We also propose an unequal subject allocation method that improves the power relative to that of the equal and symmetric allocation. The methods are illustrated using practical examples.

Performance Evaluation of Heat Exchangers in OTEC Using Ammonia/Water Mixture as Working Fluid

The ocean thermal energy conversion (OTEC) system is a promising solution to provide stable electricity supply. Although the available temperature difference in OTEC systems is small, an ammonia/water mixture as working fluid is expected to decrease irreversible losses in the heat exchangers and to improve system performance. However, in actual heat exchangers, an adequate temperature crossing does not occur in the condenser but in the evaporator. Therefore, clarification of this characteristic is important. To date, the logarithmic temperature difference (LMTD) method is used in performance evaluations of OTEC heat exchangers. This method is of limited use if physical properties of fluids vary. A generalized mean temperature difference (GMTD) method is introduced to perform this evaluation. As changes in fluid property values can be considered in the GMTD method, method dependencies on heat exchanger characteristics, effectiveness, and system characteristics can be studied. In particular, GMTD and LMTD using a pure substance were found to be almost equal. Mean temperature differences using mixtures as working fluid were higher in the evaporator, but lower in the condenser, from the GMTD method than from the LMTD method. For higher ammonia concentrations in ammonia/water mixtures, the mean temperature differences from both methods are different.

Parameter Estimation and Prediction of the Chirp and Stochastic Pulse Position Modulation Combined Signal

Recent work has proposed a certainty trend (CT) elimination technique employed for the auto-regressive/auto- regressive and moving-average (AR/ARMA) model pulse position prediction. In this paper, we investigate the intra pulse parameter estimation and pulse position prediction of the chirp and stochastic pulse position modulation (CSPPM) combined signal. The quick dechirp method is adopted to the initial frequency and chirp rate estimation. To get a stationary data series satisfying the premise condition of the AR/ARMA model prediction, a least square fitting (LSF) scheme to remove the CT term contained in pulse position sequence is presented. Compared with the classic logarithmic difference conversion (LDC) smooth method, AR/ARMA prediction performance via LSF has a significant improvement, about 70% to 96% for AR prediction and 42% to 99% for ARMA prediction. 

A characterization of the optimal sets for self-similar measures with respect to the geometric mean error

Let μ be a self-similar measure on ℝq associated with a set of contractive similitudes \({\{S_{i}\}}_{i=1}^{N}\) and a probability vector \({(p_{i})}_{i=1}^{N}\). Assume that \({\{S_{i}\}}_{i=1}^{N}\) satisfies the strong separation condition. In terms of the n-optimal sets for a finite number n∈ℕ, we give a characterization for the n-optimal sets for all n∈ℕ in the quantization for μ with respect to the geometric mean error. As an application, we determine the convergence order for the logarithmic difference of the asymptotic geometric mean error. This characterization also allows us to show that the μ-measure of every element of an arbitrary Voronoi partition with respect to an n-optimal set is uniformly comparable with n−1, provided that μ vanishes on every hyperplane in ℝq.

Linearization of hyperbolic finite-time processes

We adapt the notion of processes to introduce an abstract framework for dynamics in finite time, i.e. on compact time-sets. For linear finite-time processes a notion of hyperbolicity namely exponential monotonicity dichotomy (EMD) is introduced, thereby generalizing and unifying several existing approaches. We present a spectral theory for linear processes in a coherent way, based only on a logarithmic difference quotient. In this abstract setting we introduce a new topology, prove robustness of EMD and provide exact perturbation bounds. We suggest a new, intrinsic approach for the investigation of linearizations of finite-time processes, including finite-time analogues of the local (un-)stable manifold theorem and theorem of linearized asymptotic stability. As an application, we discuss our results for ordinary differential equations on a compact time-interval.

Numerical analysis of the tubular heat exchanger designed for co-generating units on the basis of microturbines

The application of numerical simulations using the computational fluid dynamics (CFD) analysis when mapping processes in the course of which the heat transmission occurs has become an essential part of the heat transfer systems. The present contribution deals with the possibility to use the waste heat of the flue gas produced by small microturbines. The waste heat is mapped by means of both the numerical simulations applying the FLUENT software and the practical experiment. Utilizing a part of the waste heat for water heating and decreasing the outlet temperature of the flue gas into atmosphere when applying in co-generating units represents one of the partial benefits. The present paper brings information concerning the newly designed type of heat exchanger including the results of its numerical analysis.The analysed heat exchanger designed in the system with microturbine (MT) C30 reached generally the efficiency of 75%. Both the results of simulations and the carried out practical experiment confirmed the temperature of the flue gas to be sufficient behind the exchanger to prevent the condensation of water from the flue gas. On the contrary, except for heating water the exchanger under consideration offers – thanks to its design – also other possibilities to use of the flue gas. The practical experiment confirmed the results of the CFD prediction with rather small differences as the temperature of water obtained from the exchanger was 359K and the designed shape of the exchanger did not result in substantial pressure losses in flue gas approximately 50Pa. The mean logarithmic temperature difference of the mapped and verified exchanger was ∼203K.

Logarithmic Mean Pressure Difference—A New Concept in the Analysis of the Flow Distribution in Parallel Channels of Plate Heat Exchangers

This paper deals with a new concept of logarithmic mean pressure difference (LMPD) to find an accurate mean or true friction coefficient for variable flow in parallel flow channels of the plate heat exchangers while considering the first and the last channel pressure drops. This is analogous to the log mean temperature difference (LMTD) used for the computation of heat transfer in heat exchangers. A method has been suggested to improve the computation of mean or a newly defined “true friction factor” and the mean velocity for considerable flow variations in the channels. A comparative study has been made between the conventional average friction factor and the true mean friction factor for large parallel channels. The results have also been compared between the mean channel pressure drop and LMPD for different sizes of the channels. The analysis shows that the mean channel pressure drop of parallel channels can be predicted accurately by using the so-called true mean friction factor rather than the average friction factor. Using the LMPD method, one can find the last channel pressure drop by knowing the first channel pressure drop of the plate package. Hence, the nature of flow distribution in parallel channels can be predicted easily.

무선인지시스템을 위한 Kullback-Leiber Divergence 기반의 스펙트럼 센싱 기법

본 논문에서는 무선인지시스템에서 효율적으로 스펙트럼 센싱을 수행하기 위해, 확률 분포 사이의 대수 차를 측정하는 Kullback-Leiber divergence기반의 새로운 스펙트럼 센싱 기술을 제안한다. 제안된 센싱 기법은 특정 센싱 구간에서의 국부 센싱 측정값들이 잡음 분포에서 발생하였는지, 기사용자 신호에서 발생하였는지를 Kullback-Leiber divergenc를 이용하여 판단한다. 시뮬레이션 을 통해, 제안된 Kullback-Leiber divergence기반의 스펙트럼 센싱 기법이 동일 조건에서 에너지 검출 기반의 스펙트럼 센싱 기법보다 더 좋은 성능을 제공할 수 있음을 보였다. 특히, 페이딩 환경 및 기사용자 신호의 SNR값이 낮은 경우에 에너지 검출 기반의 스펙트럼센싱 기법과 비교할 때 제안된 기법의 성능이 크게 향상됨을 보였다. In the paper, an information divergence called Kullback-Leiber divergence, which measures the average of the logarithmic difference between two probability density functions, is utilized to derive a novel method for spectrum sensing in cognitive radio systems. In the proposed sensing method, we test whether the observed samples are drawn from the noise distribution by using Kullback-Leiber divergence. It is shown by numerical results that under the same conditions, the proposed Kullback-Leiber divergence-based spectrum sensing always outperforms the energy detection based spectrum sensing significantly, especially in low SNR regime and in fading circumstance.

Hydrogen Mass Transport in Fuel Cell Gas Diffusion Electrodes

AbstractAn oxygen transport model derived for limiting current density operation was employed to explore its use for hydrogen transport. Limiting current data obtained from a variety of fuel cell designs (alkaline, proton exchange membrane, sulphuric acid) demonstrated the model's validity and allowed determination of the hydrogen mass transport coefficient, a key cell performance parameter. Under specific operating conditions, the proposed model is consistent with the continuous stirred tank reactor and the logarithmic mean concentration difference models. The proposed model is preferable because it is more general and derived from a specific physical mechanism. Experimental precautions needed to ensure well‐defined limiting currents without the presence of artefacts were reemphasized and expanded. Model use for predictive purposes is also briefly discussed.

An intracellular glucose biosensor based on nanoflake ZnO

In this study, a potentiometric intracellular glucose biosensor was fabricated by immobilization of glucose oxidase on nanoflake ZnO. Nanoflake ZnO with a wall thickness around 200 nm was grown on the tip of a borosilicate glass capillary and used as a selective intracellular glucose biosensor for the measurement of glucose concentrations in human adipocytes and frog oocytes. The results showed a fast response within 4 s and a logarithmic linear glucose-dependent electrochemical potential difference over a wide range of glucose concentration (500 nM–10 mM). Our measurements of intracellular glucose were consistent with the values of intracellular glucose concentrations reported in the literature. The monitoring capability of the sensor was demonstrated by following the increase in the intracellular glucose concentration induced by insulin in adipocytes and frog oocytes. In addition, the nanoflake ZnO material provided 1.8 times higher sensitivity than previously used ZnO nanorods under the same conditions. Moreover, the fabrication method in our experiment is simple and the resulting nanosensor showed good performance in sensitivity, stability, selectivity, reproducibility, and anti-interference. All these results demonstrate that the nanoflake ZnO can provide a promising material for reliable measurements of intracellular glucose concentrations within single living cells.

Diagnostic Equivalence of an N-terminal Pro-Brain Natriuretic Peptide Point-of-Care Test to the Laboratory Method in Patients With Heart Failure and in Reference Populations

Context: Point-of-care assays allow to have analytical results available at the site of patient care delivery such as the emergency department or the intensive care unit. Objective: To demonstrate equivalence in the N-terminal (NT) pro-brain natriuretic peptide (proBNP) concentrations as measured by the point-of-care assay (POC NT-proBNP) in comparison to the laboratory assay (lab NT-proBNP) in patients with heart failure and in a reference population. Design: Multicenter study at 7 sites. The following were eligible for data analysis: 217 patients with heart failure and 189 individuals from a reference population (patients with hypertension, diabetes, chronic obstructive pulmonary disease or asthma, or apparently healthy individuals). For all study participants, NT-proBNP values both with the POC and with the laboratory assay, echocardiographic and spirometry data, and the New York Heart Association classification were available. Results: In method comparisons between POC NT-proBNP and lab NT-proBNP, the slope of the regression line was 0.99 and the correlation coefficient was 0.97. Testing on diagnostic equivalence, POC NT-proBNP versus lab NT-proBNP yielded a mean logarithmic methodical difference of −4.9% in patients with heart failure and +3.5% with the reference population. Using an age-independent cutoff of 125 ng/L, the diagnostic sensitivity of POC NT-proBNP and of lab NT-proBNP was found to be 89%, and the areas under the receiver operating characteristic curves were 0.88 or 0.89, respectively. Conclusions Our multicenter study has demonstrated the diagnostic equivalence of POC NT-proBNP with lab NT-proBNP both in the diagnosis of heart failure and in the differential diagnosis of a reference population. Consequently, clinical experiences and indications with the laboratory assay could be applied to the POC assay as well.

Small-spatial-scale variations of nebular properties and the abundance discrepancy in three Galactic H ii regions★

We present the results of long-slit spectroscopy in several slit positions that cover different morphological structures of the central parts of three bright Galactic H ii regions: M8, M17 and NGC 7635. We study the spatial distributions of a large number of nebular parameters, such as the extinction coefficient, line fluxes, physical conditions and ionic abundances at the maximum spatial resolution attainable with our instrumentation. Particularly, our goal is to study the behaviour of the abundance discrepancy factor of O2+[ADF(O2+)], defined as the logarithmic difference of the O2+ abundances derived from collisionally excited and recombination lines. We find that ADF(O2+) remains fairly constant along the slit positions of M8 and M17. For NGC 7635, we only detect the O ii recombination lines in the integrated spectrum along the whole slit, where ADF(O2+) reaches a remarkably high value of about 0.59 dex. We compare our results with previous results obtained for the Orion Nebula. We find much evidence to suggest the presence of a candidate Herbig–Haro object in M8.

A modified logarithmic mean enthalpy difference (LMED) method for evaluating the total heat transfer rate of a wet cooling coil under both unit and non-unit Lewis Factors

The logarithmic mean enthalpy difference, (LMED) method has been extensively used in evaluating the thermal performance of an air cooling coil under wet condition. The LMED method has been developed based on the assumption of unit Lewis Factor, i.e., Le 2/3 = 1. However, a number of previous studies have suggested that the Lewis Factor can actually deviate from being 1. Consequently, errors can be resulted in when calculating the total heat transfer rate of a wet cooling coil using the LMED method. Therefore, a modified LMED (m-LMED) method has been developed for calculating the total heat transfer rate under both unit and non-unit Lewis Factors and is reported in this paper. This m-LMED method has been validated by comparing its prediction of the total heat transfer rate to that from numerically solving the fundamental governing equations of heat and mass transfer of a wet cooling coil. The m-LMED method can therefore replace the LMED method for calculating the total heat transfer rate of a wet cooling coil under both unit and non-unit Lewis Factors.

A210 アンモニア/水を用いた海洋温度差発電の評価方法(太陽光と温度差発電・熱回収,OS2 自然エネルギー)

An ammonia/water as working fluid is used for the ocean thermal energy conversion system (OTEC) to decrease an irreversible loss in heat exchangers. And this fluid is expected to improve the system performance. It is important to clear the characteristic and the true evaluation of heat exchanger in OTEC ststem. Therefore, it is important that the clarification of characteristic in heat exchangers. At this time, logarithmic temperature difference (LMTD) method that is limited when considered that physical properties of fluids are constant is used for the performance evaluation in heat exchangers in OTEC. Then, a generalized mean temperature difference (GMTD) method that can consider the change of the physical properties value of fluids is introduced into the evaluation of characteristics of heat exchangers that uses ammonia/water in this paper. GMTD was introduced into the evaluation of heat exchangers of OTEC using ammonia/water and the influence given to the evaluation of the characteristic, effectiveness, and system characteristics was clarified.

Mortality, or Probability of Death, from a Suicidal Act in the United States

The probability of death resulting from a suicidal act as a function of age is explored. Until recently, data on suicide attempts in the United States were not available, and therefore the relationship between attempts and completed suicide could not be systematically investigated. Now, with new surveillance of self-harm data from the Centers for Disease Control, our examination found that (1) the mortality among self-harmers fits an exponential function of age and (2) the logarithmic difference between female and male suicidal mortality increases in direct proportion to age from puberty to menopause. The mortality exponential function of age is a description that provides a life-span perspective of suicide and suggests data-informed criteria for future suicide and public health research.

Simultaneous in vivo synchrotron radiation computed tomography of regional ventilation and blood volume in rabbit lung using combined K-edge and temporal subtraction

In K-edge subtraction (KES) imaging with synchrotron radiation computed tomography (SRCT), two images are taken simultaneously using energies above and below the K-absorption edge of a contrast agent. A logarithmic difference image reveals the contrast agent concentration with good accuracy. Similarly, in temporal subtraction imaging (TSI) the reference image is taken before the introduction of the contrast agent. Quantitative comparisons of in vivo images of rabbit lung indicated that similar results for concentrations of iodine in blood vessels and xenon in airways are obtained by KES and TSI, but the level of noise and artifacts was higher in the latter. A linear fit showed that in the lung parenchyma ρTSI = (0.97 ± 0.03)ρKES + (0.00 ± 0.05) for xenon and ρTSI = (1.21 ± 0.15)ρKES + (0.0 ± 0.1) for iodine. For xenon the calculation of time constant of ventilation gave compatible values for both of the methods. The two methods are combined for the simultaneous determination of the xenon concentration (by KES) and the iodine concentration (by TSI) in lung imaging, which will allow simultaneous in vivo determination of ventilation and perfusion.