A comment on “Returns to scale and scale elasticity in data envelopment analysis”

Fukuyama [Fukuyama, H., 2000. Returns to scale and scale elasticity in data envelopment analysis. European Journal of Operational Research 125, 93–112] provided some characterizations of scale elasticity and returns to scale in DEA. In this paper, we present some counterexamples and comments to the main lemma of the afore-mentioned paper, based on which Fukuyama’s idea has been built.     

Interpolatory Pointwise Estimates for Polynomial Approximation

We discuss whether or not it is possible to have interpolatory pointwise estimates in the approximation of a function f∈ C[0,1] , by polynomials. For the sake of completeness, as well as in order to strengthen some existing results, we discuss briefly the situation in unconstrained approximation. Then we deal with positive and monotone constraints where we show exactly when such interpolatory estimates are achievable by proving affirmative results and by providing the necessary counterexamples in all other cases. November 16, 1998. Date revised: July 12, 1999. Date accepted: September 13, 1999.     

Some properties of semi-E-convex functions

In this paper, we show that Theorems 4.2, 4.3 and 4.6 in [Youness, J. Optim. Theory Appl. 102 (1999) 439-450] are incorrect by giving some counterexamples. We introduce a new class of semi-E-convex function and discuss some its basic properties.     

Comments on “The stability and control of fractional nonlinear system with distributed time delay” [Appl. Math. Model. 40 (2016) 3257–3263]

In this comment, we give four counterexamples to show that Conclusion 1, Conclusion 2, Theorem 1 and Theorem 2 of a recent paper [1] are incorrect.     

Orlicz型序列空间的暴露性

对赋Luxember范数或Orlicz范数的Orlicz型序列空间,诸如古典的、广义的及参数式的,本文总结、补充、比较列出了暴露点及暴露性的充分必要刻画,并对以往结果中的错误进行了修正,从而在序列空间方面系统地完成了有关暴露性的刻画。     

Modifications of higher-order convergence for solving nonlinear equations

In [Liang Fang, Guoping He, Some modifications of Newton’s method with higher-order convergence for solving nonlinear equations, J. Comput. Appl. Math. 228 (2009) 296-303], the authors pointed out that the iteration constructed in [Y.M. Ham, C.B. Chun and S.G. Lee, Some higher-order modifications of Newton’s method for solving nonlinear equations, J. Comput. Appl. Math. 222 (2008) 477-486] failed when p=2. They gave some counterexamples and obtained a modified result. However, they did not show the essential reason which leads to the incorrect result. In this paper, we shall show that reason and present more general results than the above-mentioned papers.     

On the optimality of compactness results for interpolation methods associated to polygons

Compactness results of Cobos and Peetre [3] guarantee that the interpolated operator is compact assuming that all but two restrictions of the operator (located in adjacent vertices) are compact. Comparing these results with others in the literature, one might expect that the same conclusion holds under weaker compactness conditions. However, the Cobos—Peetre results are best possible as we show by means of counterexamples.     

关于度量及纲函数的Hausdorff测度的两个反例

本文研究了度量空间中Hausdorff测度与度量及纲函数的关系.利用拓扑学及Hausdorff测度论中一些性质,构造了两反例来说明存在不等价纲函数g,h和某一紧度量空间(ρ,X),使得Hρ,g与Hρ,h对此紧度量空间等价等问题.这些反例有助于从另一个角度理解文胜友、文志英[4]中主要结果.     

A loosely Bernoulli counterexample machine

In Rudolph’s paper on minimal self joinings [7] he proves that a rank one mixing transformation constructed by Ornstein [5] can be used as the building block for many ergodic theoretical counterexamples. In this paper we show that Ornstein’s transformation can be altered to create a general method for producing zero entropy, loosely Bernoulli counter-examples. This paper answers a question posed by Ornstein, Rudolph, and Weiss [6].     

A note on orthodox semidirect products and wreath products of monoids

In the present note, we show that the restriction which Saito imposed on S in [3] is not necessary: S may be a semigroup without unity. Secondly, we investigate the wreath products of semigroups and obtain our main results, Theroem 2.3 and Corollary 2.4. We find also that groups in [3] may be replaced by right groups in [1]. Undefined terminology and notation may be found in [3] and [1] unlesss otherwise stated.     

"求线性规划问题可行基的一种方法"的再注记

文[1]给出一个求线性规划问题可行基的方法，文[2]指出其判定条件（3）有误，然而所用的反例并不正确。本文给出三个正确的反例；此外，还给出反例表明文[1]的判定条件（2）也不正确的。     

Separation in topological algebras

One of the basic results from the theory of topological groups is that aT ₀ topological group is already completely regular. It is also known [1] thatT ₀ quasigroups are regular. Taylor [8] showed that a fragment of these results holds in any congruence permutable variety, namely that in such a variety aT ₀ topological algebra is already Hausdorff. Gumm [2] extended this result to 3-permutable varieties and showed that, more generally,T ₀ topological algebras in congruencen-permutable varieties areT ₁. In this paper we show thatT ₀ topological algebras inn-permutable varieties satisfy a separation condition strictly stronger thanT ₁. We also give some counterexamples that show that some of these separation results are the best possible.Presented by S. Burris.This research was part of the author's thesis at The University of Colorado, directed by Walter Taylor. The author wishes to thank professor Taylor for his many contributions.     

On Fuglede's Conjecture and the Existence of Universal Spectra

Recent methods developed by Tao [18], Kolountzakis and Matolcsi [7] have led to counterexamples to Fugelde’s Spectral Set Conjecture in both directions. Namely, in Tao produced a spectral set which is not a tile, while Kolountzakis and Matolcsi showed an example of a nonspectral tile. In search of lower dimensional nonspectral tiles we were led to investigate the Universal Spectrum Conjecture (USC) of Lagarias and Wang [14]. In particular, we prove here that the USC and the "tile → spectral" direction of Fuglede’s conjecture are equivalent in any dimensions. Also, we show by an example that the sufficient condition of Lagarias and Szabó [13] for the existence of universal spectra is not necessary. This fact causes considerable difficulties in producing lower dimensional examples of tiles which have no spectra. We overcome these difficulties by invoking some ideas of Révész and Farkas [2], and obtain nonspectral tiles in . Fuglede’s conjecture and the Universal Spectrum Conjecture remains open in 1 and 2 dimensions. The one-dimensional case is closely related to a number theoretical conjecture on tilings by Coven and Meyerowitz [1].     

The Vietoris hyperspace structure for approach spaces

We show that there exists a natural approach version of the topological Vietoris hyperspace construction [16], [17] which has several advantages over the topological version. In the first place the important structural fact that the Vietoris construction can now also be considered, not only for topological but also intrinsically for metric spaces, but equally important in the second place the fact that we can considerably strengthen fundamental classic results. In this paper we mainly pay attention to properties concerning or involving compactness. As main results, in the first place we prove that it is not merely compactness of the Vietoris hyperspace which is equivalent to compactness of the original space [3] but that actually in the approach setting the indices of compactness [7], [8], [9], [10] numerically completely coincide. In the second place the well-known result [3], [4], [15] which says that if the original space is compact metric then the Vietoris topology is metrizable by the Hausdorff metric gets strengthened in the sense that in the approach setting under the same conditions the Vietoris approach structure actually coincides with the Hausdorff metric. Classic results follow as easy corollaries. Besides these main results we also draw attention to the good functorial relationship between the Vietoris approach structures and the associated topologies.     

Hamiltonicity of 3-connected line graphs

Thomassen conjectured that every 4-connected line graph is Hamiltonian. Lai et al. conjectured [H. Lai, Y. Shao, H. Wu, J. Zhou, Every 3-connected, essentially 11-connected line graph is Hamiltonian, J. Combin. Theory Ser. B 96 (2006) 571–576] that every 3-connected, essentially 4-connected line graph is Hamiltonian. In this note, we first show that the conjecture posed by Lai et al. is not true and there is an infinite family of counterexamples; we show that 3-connected, essentially 4-connected line graph of a graph with at most 9 vertices of degree 3 is Hamiltonian; examples show that all conditions are sharp.     

A note on “Single-machine scheduling problems with both deteriorating jobs and learning effects”

The main results in a recent paper [1] (J.-B. Wang, D. Wang, G.-D. Zhang, Single-machine scheduling problems with both deteriorating jobs and learning effects, Appl. Math. Model. 34 (2010) 2831–2839) are incorrect because job processing times are variable due to both deteriorating jobs and learning effects, which is not taken into account by the authors. In this note, we show by counter-examples that some published results are incorrect.     

Corrigendum to “A novel approach to multi attribute group decision making based on trapezoidal interval type-2 fuzzy soft sets” [Appl. Math. Model. 37 (2013) 4948–4971]

The aim of this paper is to show by counterexamples that assertions (3) and (4) of Theorem 3.2, and assertions (3) and (5) of Theorem 3.5 in a previous paper by the authors [Appl. Math. Model. 37 (2013) 4948-4971] are incorrect and offer their modified versions.     

On some properties of the ε-core of games with coalition structure

Chang [1991] stated some inclusion relation about kernel, reasonable set, and ε-core of games with coalition structure. We give counterexamples and modify erroneous results. Received: May 1997/Revised version: January 1999     

A note on flow shop scheduling problems with deteriorating jobs on no-idle dominant machines

The main results in a recent paper [M. Cheng, S. Sun, L. He, Flow shop scheduling problems with deteriorating jobs on no-idle dominant machines, European Journal of Operational Research 183 (2007) 115–124] are incorrect because job processing times are variable due to deteriorating effect, which is not taken into account by the authors. In this note, we show first by counter-examples that the published results are incorrect, and then we provide corrected results.