Mean instantaneous firing frequency is always higher than the firing rate

Frequency coding is considered one of the most common coding strategies employed by neural systems. This fact leads, in experiments as well as theoretical studies, to construction of so-called transfer functions, where the output firing frequency is plotted against the input intensity. The term "firing frequency" can be understood differently in different contexts. Basically, it means that the number of spikes over an interval of preselected length is counted and then divided by the length of the interval, but due to the obvious limitations, the length of observation cannot be arbitrarily long. Then firing frequency is defined as reciprocal to the mean interspike interval. In parallel, an instantaneous firing frequency can be defined as reciprocal to the length of current interspike interval, and by taking a mean of these, the definition can be extended to introduce the mean instantaneous firing frequency. All of these definitions of firing frequency are compared in an effort to contribute to a better understanding of the input-output properties of a neuron.     

Mechanism of attenuation coefficient variability of underwater upward radiance

Upward radiance is the signal source of ocean colour remote sensing. Its attenuation characteristics along with water depth not only determine the water-leaving radiance but are also the key parameters that reflect water-quality conditions. Assuming that the water is optically homogeneous in the vertical direction, this study calculates the attenuation coefficient of upward radiance (ACUR) under conditions with different zenith angles and absorption and scattering coefficients using the radiative transfer model coupled with multiple scattering. Then, the attenuation mechanism of upward radiance is discussed. The results obtained indicate the following. (1) The ACUR under the condition of a large zenith angle gradually decreased and subsequently increased with the increasing scattering coefficient when the absorption was less. The variation trend of the ACUR was gradually weakened with increasing absorption coefficients. (2) The ACUR at a small zenith angle increased approximately linearly with the increasing scattering coefficient; subsequently, this trend gradually disappeared. At the same time, the change rate of ACUR first increased and then decreased with increasing scattering when the absorption coefficient increased. (3) The absorption coefficient has the greatest contribution to the ACUR. When the scattering/absorption ratio is between 0.5 and 37, the corresponding contribution ratio is in the range of 90.3–98.5%. (4) When the ratio is less than 1.5, the contribution of the zenith angle to the ACUR is greater than that of the scattering coefficient, and the corresponding contribution ratios ranged from 2.2% to 7.3% and from 3.7% to 17.9%. With the increasing ratio, the contribution of the scattering coefficient to the ACUR was more than that of the zenith angle, and then this trend became stable. The results were validated by field observation data from Lake Taihu (China).     

一种融合变异系数的k-mean聚类分析方法

K-means聚类算法的性能依赖于距离度量的选择,k-means算法将欧几里德距离作为最常用的距离度量方法。欧氏距离认为所有属性在聚类中作用是相同的,但是这种距离度量方法并不能准确反映样本间的相异性。针对这种不足,提出了融合变异系数的k-means聚类分析方法（CV-k-means）,利用变异系数权重向量来减少不相关属性的影响。实验结果表明,该方法的聚类结果优于k-means算法。     

Applications of the cluster variation method to empirical phase diagram calculations

The treatment of short- and long-range order is an important problem in the modelling of solid solutions, and therefore in the modelling of order-disorder phase transitions. This can be correctly handled by the cluster variation method (CVM). The basis of this method are briefly recalled. The methods of resolution of the CVM are outlined with their advantages and disadvantages. The input parameters of the CVM are the cluster interactions which can be obtained either by ab-initio calculations of total energies (or energies of mixing) or by fitting thermodynamic experimental data. This last method, called the mixed CVM-CALPHAD, has been used in the past to calculate binary and ternary systems. Some examples are given, and the various strategies employed are described. A review of the systems, binaries and ternaries, for which the mixed CVM-CALPHAD has been used to compute the phase diagram is proposed.     

Video frame and region duplication forgery detection based on correlation coefficient and coefficient of variation

Multimedia Tools and Applications - In this paper, we present a passive blind scheme consisting of two different algorithms to detect frame and region duplication forgeries in videos. We have...     

An empirical analysis of smartphone personalisation: measurement and user variability

The present report is an empirical analysis of smartphone personalisation. We collected data from two groups of users to measure how they adapt the content, interface and physical appearance of their devices. This user-driven personalisation is measured with a simple heuristic approach to quantify the behaviour. Using these scores, we explore how users differ from each other in how they personalise their smartphones with a focus on gender differences, usability and device usage in the wild. Among our findings are that not all users personalise their smartphones, females and males personalise their iPhones differently, and those who personalised their phones more tended to rate it as more usable. The users who personalised more also used their device for greater periods of time on a broader range of applications. For instance, individuals who adapted their iPhones to a greater degree also accessed the Web more often and spent more time browsing once it was accessed. We conclude with a discussion of possible factors underlying the large user diversity of smartphone personalisation found in this research.     

Existence of an optimum dynamic coefficient of friction and the influence on human gait variability

The existence of a range of optimal coefficient of friction that encompasses safety and comfort has not been addressed before. This paper assesses the existence of such a range and its relationship with the variability of human gait. Six women walked for 15 min over five ceramic tile floorings with friction coefficients (DCOF) ranging from 0.19 to 0.63. Subjective opinions (pain, comfort, etc.) and biomechanical parameters including sagittal plane knee angle, tibia acceleration, and ground reaction forces were gathered. The required coefficient of friction (RCOF) was calculated from ground reaction forces. The results show that as DCOF increases so do reports of pain in the knees and under the metatarsal heads and toes; whereas a low DCOF relates to pain in the thighs and perception of low friction. RCOF showed a quadratic relationship with DCOF indicating the existence of a range of optimal coefficient of friction outside of which walking strategy is modified either to avoid slipping (DCOF < 0.25) or reduce pain (DCOF > 0.55). This result is supported by the results of the analysis of gait variability using non-linear methods. Floors inside the optimal range of friction yielded statistically significant higher entropy for tibia acceleration and knee angle, confirming the hypothesis that gait is more constrained outside that range (i.e. natural variability is reduced).Relevance to the industry: Floor friction is one of the main concerns for the floor industry and for decision makers when choosing public space paving (indoor and outdoor). The false concept ‘the more friction the better’ can induce manufacturers and technicians to make wrong decisions. This paper can assist the industry produce and select solutions encompassing safety and comfort.     

Evaluating the accessibility of higher education institution websites in the State of Kuwait: empirical evidence

Universal Access in the Information Society - The objective of this study&nbsp;is to evaluate the current state of accessibility of higher education institution websites in the State of Kuwait....     

Computing the range of values of real functions with accuracy higher than second order

Given a continuous functionf:D→? on a compact interval \(D \subseteq \mathbb{R}\) we consider the problem of finding an intervalV(f, X) that contains the range of the values off,W(f, X)={f(x)‖x∈X} on a subintervalX?D. To reach this goal we use methods from interval-arithmetic. WhenV(f, X) is computed by one of the well-known methods from literature for a sequence {X _n } of intervals with decreasing diametersd(X _n )→0, then generally the overestimation ofW(f, X _n ) byV(f, X _n ) will decrease at most quadratically withd(X _n ). The method presented in this paper, however, allows the computation ofV(f, X _n ) such that this overestimation decreases with an arbitrary powers>0 ofd(X _n ). Theoretically any powers∈? is possible, in practice, however, 1≤s≤4 can be reached with little or moderate amount of work ands=5 ors=6 with some more work. A generalization to functionsf: ? ⁿ ?? is given at the end of the paper.     

A new exponentially weighted moving average control chart for monitoring the coefficient of variation

Monitoring coefficient of variation is one of the successful approaches to Statistical Process Control (SPC) when the process mean and standard deviation are not constants. This paper presents a modified Exponentially Weighted Moving Average (EWMA) chart in order to further enhance the sensitivity of the EWMA control chart proposed by Castagliola et al. (2011). Tables are provided for the statistical properties of the new chart. Some numerical results and comparisons are given and show that the new chart has an average run length performance that is superior to some other competing procedures. A real data example from manufacturing shows that it performs quite well in applications.     

基于变异系数的分形图像压缩稀疏编码算法

针对分形图像编码算法复杂度高、编码时间冗长的问题,提出正交稀疏编码和纹理特征提取表示图像块的方法.首先,灰度级的正交稀疏变换提高了图像的重建质量和解码时间.其次,相关系数矩阵度量范围块和域块之间的变异系数特征降低了冗余度和编码时间.仿真实验结果显示,该方法与传统的分形图像编码算法相比,图像重建质量更好,编码速度更快.     

Optimal Behavior is Easier to Learn than the Truth

We consider a reinforcement learning setting where the learner is given a set of possible models containing the true model. While there are algorithms that are able to successfully learn optimal behavior in this setting, they do so without trying to identify the underlying true model. Indeed, we show that there are cases in which the attempt to find the true model is doomed to failure.     

Multi-dimensional students’ evaluation of e-learning systems in the higher education context: An empirical investigation

There has been little research on assessment of learning management systems (LMS) within educational organizations as both a web-based learning system for e-learning and as a supportive tool for blended learning environments. This study proposes a conceptual e-learning assessment model, hexagonal e-learning assessment model (HELAM) suggesting a multi-dimensional approach for LMS evaluation via six dimensions: (1) system quality, (2) service quality, (3) content quality, (4) learner perspective, (5) instructor attitudes, and (6) supportive issues. A survey instrument based on HELAM has been developed and applied to 84 learners. This sample consists of students at both undergraduate and graduate levels who are users of a web-based learning management system, U-Link, at Brunel University, UK. The survey instrument has been tested for content validity, reliability, and criterion-based predictive validity. The analytical results strongly support the appropriateness of the proposed model in evaluating LMSs through learners’ satisfaction. The explanatory factor analysis showed that each of the six dimensions of the proposed model had a significant effect on the learners’ perceived satisfaction. Findings of this research will be valuable for both academics and practitioners of e-learning systems.     

Multi-dimensional students’ evaluation of e-learning systems in the higher education context: An empirical investigation

There has been little research on assessment of learning management systems (LMS) within educational organizations as both a web-based learning system for e-learning and as a supportive tool for blended learning environments. This study proposes a conceptual e-learning assessment model, hexagonal e-learning assessment model (HELAM) suggesting a multi-dimensional approach for LMS evaluation via six dimensions: (1) system quality, (2) service quality, (3) content quality, (4) learner perspective, (5) instructor attitudes, and (6) supportive issues. A survey instrument based on HELAM has been developed and applied to 84 learners. This sample consists of students at both undergraduate and graduate levels who are users of a web-based learning management system, U-Link, at Brunel University, UK. The survey instrument has been tested for content validity, reliability, and criterion-based predictive validity. The analytical results strongly support the appropriateness of the proposed model in evaluating LMSs through learners’ satisfaction. The explanatory factor analysis showed that each of the six dimensions of the proposed model had a significant effect on the learners’ perceived satisfaction. Findings of this research will be valuable for both academics and practitioners of e-learning systems.     

Effect of the solvent on the conformational behavior of the alanine dipeptide deduced from MD simulations

In general, peptides do not exhibit a well-defined conformational profile in solution. However, despite the experimental blurred picture associated with their structure, compelling spectroscopic evidence shows that peptides exhibit local order. The conformational profile of a peptide is the result of a balance between intramolecular interactions between different atoms of the molecule and intermolecular interactions between atoms of the molecule and the solvent. Accordingly, the conformational profile of a peptide will change upon the properties of the solvent it is soaked. To get insight into the balance between intra- and intermolecular interactions on the conformational preferences of the peptide backbone we have studied the conformational profile of the alanine dipeptide in diverse solvents using molecular dynamics as sampling technique. Solvents studied include chloroform, methanol, dimethyl sulfoxide, water and N-methylacetamide. Different treatments of the solvent have been studied in the present work including explicit solvent molecules, a generalized Born model and using the bulk dielectric constant of the solvent. The diverse calculations identify four major conformations with different populations in the diverse solvents: the C₇^eq only sampled in chloroform; the C₅ or extended conformation; the polyproline (PII) conformation and the right-handed α-helix conformation (α_R). The results of present calculations permit to analyze how the balance between intra- and intermolecular interactions explains the populations of the diverse conformations observed.     

Mobile and ubiquitous learning in higher education settings. A systematic review of empirical studies

Mobile and ubiquitous learning are increasingly attracting academic and public interest, especially in relation to their application in higher education settings.The systematic analysis of 36 empirical papers supports the view that knowledge gains from instructionist learning designs are facilitated by distributed and more frequent learning activities enabled by push mechanisms. They also lend themselves to the activation of learners during classroom lectures. In addition, and as a particular advantage of mobile technology, “hybrid” designs, where learners create multimodal representations outside the classroom and then discussed their substantiated experiences with peers and educators, helped to connect learning in formal and more informal and personalized learning environments.Generally, empirical evidence that would favour the broad application of mobile and ubiquitous learning in higher education settings is limited and because mobile learning projects predominantly take instructionist approaches, they are non-transformatory in nature. However, by harnessing the increasing access to digital mobile media, a number of unprecedented educational affordances can be operationalised to enrich and extend more traditional forms of higher education.     

基于摩擦系数的扩散模型

根据分子间摩擦系数与组分自扩散系数关系,提出一个新的互扩散系数模型。模型分为3部分：组成项、自扩散系数和化学势与组分关系。采用文献自扩散系数值,并用不同状态方程以计算化学势与组分关系,模拟1 132～1 810℃之间不同组成二氧化碳气体混合物的互扩散系数,并与实验值做了比较。结果表明采用Peng-Robinson(PR),Redlich-Kwong(RK)及Van der Waals(VdW)方程计算化学势与组分关系而得到的模拟结果优于Virial方程,且平均误差在5%之内。     

More than watching: An empirical and experimental examination on the impacts of live streaming user-generated video consumption

Live streaming user-generated video (UGV), a nascent format of crowdsourced content, has grown massive popularity among social media users and is believed to have substantial potential business influences. However, industry practitioners express concerns regarding this new form on social media platforms and the influences of live streaming UGV consumption lack research. Motivated such, through a uniquely merged dataset from the video game industry, we conduct a series of panel time-series empirical analyses to investigate the business value of live streaming UGV consumption. Further, we propose a conceptual framework based on the sense of community literature to understand the consequences of live streaming UGV consumption and verify it through several online experiments. This research contributes to the IS literature by shedding light on the influences of emergent crowdsourced content, providing a conceptual framework to existing literature, and offering rich managerial implications and guidelines to managers regarding utilizing live streaming UGVs.     

The use of biophysical indices and coefficient of variation derived from airborne synthetic aperture radar for monitoring the spread of aquatic vegetation in tropical reservoirs

This paper compares the use of biophysical indices and coefficients of variation derived from airborne synthetic aperture radar for discriminating and characterising land cover classes in the Tucurui reservoir. It assumes that the structural and dielectric properties of the land cover classes are sufficiently distinct to permit their discrimination using airborne C-band SAR data at different polarizations. Analyses of the results show that any of the proposed indices can be used effectively to discriminate among the land cover classes in the Tucurui reservoir. Certain combinations of polarizations and biophysical indices can, however, improve the saparability of the land cover classes.