Solving the maximal covering location problem with heuristic concentration

The metaheuristic heuristic concentration (HC) is applied here to the solution of large instances of the maximal covering location problem with high percentage coverage. In these instances, exact methods may be too cumbersome for practical use, and heuristics can allow faster solution times with near-optimal results. We examined the performance of HC based on its ability to approach the optimal solutions to these problems and the run times of the algorithm compared to LP-IP runtimes. Exact solutions, generated by linear programming and branch and bound, provided a benchmark for comparison when the LP-IP problems could be run to completion. In all cases, HC found solutions with objective values no worse than 0.543% below the best known LP-IP objective value. In several instances, LP-IP runtime ballooned to as much as 38.5 h, while HC took no longer than 1.6 h in any instance. In one particular instance, LP-IP took 38.5 h to terminate, while HC found a near-optimal solution (within 0.306% of optimality) in only 25 min. Furthermore, in 62.5% of the runs, the second stage of HC improved on the first stage 1-opt algorithm.     

Learning linear PCA with convex semi-definite programming

The aim of this paper is to learn a linear principal component using the nature of support vector machines (SVMs). To this end, a complete SVM-like framework of linear PCA (SVPCA) for deciding the projection direction is constructed, where new expected risk and margin are introduced. Within this framework, a new semi-definite programming problem for maximizing the margin is formulated and a new definition of support vectors is established. As a weighted case of regular PCA, our SVPCA coincides with the regular PCA if all the samples play the same part in data compression. Theoretical explanation indicates that SVPCA is based on a margin-based generalization bound and thus good prediction ability is ensured. Furthermore, the robust form of SVPCA with a interpretable parameter is achieved using the soft idea in SVMs. The great advantage lies in the fact that SVPCA is a learning algorithm without local minima because of the convexity of the semi-definite optimization problems. To validate the performance of SVPCA, several experiments are conducted and numerical results have demonstrated that their generalization ability is better than that of regular PCA. Finally, some existing problems are also discussed.     

Approximation by skin surfaces

We present a method to approximate a simple, regular C² surface W in by a (tangent continuous) skin surface S. The input of our algorithm is a set of approximate W-maximal balls, where the boundary of the union of these balls is homeomorphic to W. By generating patches of spheres and hyperboloids over the intersection curves of the balls the algorithm determines a one-parameter family of skin surfaces, where a parameter controls the size of the patches. The skin surface S is homeomorphic to W, and the approximate W-maximal balls in the input set are also S-maximal. The Hausdorff distance between the regions enclosed by the input surface W and the approximating skin surface S depends linearly on a parameter related to the sampling density of the approximate W-maximal balls.     

Investigating the effect of hydrogen addition on cyclic variability in a natural gas spark ignition engine: Wavelet multiresolution analysis

Using wavelet-based multiresolution analysis, this study investigates the effect of hydrogen addition on cyclic variability in a natural gas spark ignition engine. The engine is operated at 3000 rpm, and a lean combustible mixture with excess air ratio of 1.4 is used. Three cases are examined: natural gas with no hydrogen added, and natural gas with the addition of 23% and 40% hydrogen by volume. The time series of the indicated mean effective pressure are analyzed over 192 engine cycles. The method of maximal overlap discrete wavelet transform is used to decompose the time series into five levels with different frequency bands, each level consisting of a “detail” signal and an “approximation” signal. The root mean square amplitude of the detail signal at each level is used as a measure of cyclic variability. The results reveal that with the addition of 23% hydrogen, the root mean square value of the detail signal in each of the five bands is less than that for 100% natural gas. When the amount of hydrogen addition is increased to 40%, the root mean square value in each of the five bands is further reduced. In other words, hydrogen addition has a pronounced effect on reducing the cyclic variability of the indicated mean effective pressure.     

Aerobic capacity of urban women homemakers in Bombay

Twenty-six healthy women homemakers residing in the metropolitan city of Bombay were studied on a treadmill and a cycle ergometer to determine their aerobic capacity ([Vdot]O₂ max) with a view to evaluating their cardio-respiratory fitness and ascertaining the job-demand-fitness-compatibility in household activities. The [Vdot]O₂ max was found to be significantly higher in treadmill experiments, i.e. 15% in absolute value and 18% in relative value, as compared with that obtained by cycle ergometry (p < 0·001). A much higher difference was observed in values derived from the two methods on the same subjects (i.e. 28% in absolute value and 31% in relative value). Thus, the [Vdot]O₂max obtained from treadmill experiments may be regarded as the maximal aerobic power or the highest oxygen uptake that an individual can attain during exercise, which in the sample of the present study was recorded as 1·901 min ^?1 (33·9 ml kg ^?1 min ^?1). The findings also revealed that age and body weight have a direct influence on [Vdot]O₂max, which was found to be significantly correlated, positively with the latter and negatively with the former (p<0·01 in both cases). The physiological job-demand of household activities seems to be compatible in relation to the [Vdot]O₂max of the homemakers.     

Study on the shear strength of soil–rock mixture by large scale direct shear test

Soil–rock mixtures (S–RM) which formed in the quaternary period are a type of extremely inhomogeneous and loose geomaterial with a certain percentage of rock blocks. They are composed of rock blocks with various sizes and high strength, fine grained soil and pores. The meso-failure mechanism and macro-physical and mechanical characteristics of S–RM are largely controlled by its rock block proportion and the granular distribution. As we know, when the rock blocks in the S–RM are larger, it is difficult to take an in-situ sample for an on-site test. In addition, it is difficult to obtain the granular distribution of rock blocks in S–RM by traditional sieving tests. This paper uses a new method called digital image processing (DIP) in which the rock blocks in S–RM samples are separated from the soil matrix, and the proportion and distribution of the rock blocks is obtained quantitatively. The results are used for the sample preparation of the large scale direct shear tests which provide a new method for the test study of S–RM. According to the results of large scale direct shear tests the rock block size proportion controls the deformation and fracture mechanism of the S–RM. The shape of the shear stress vs horizontal displacement curve and the vertical displacement vs horizontal displacement curve of the S–RM samples are different from that of general “soil” and “rock”. With the increment of the rock block proportion the shear band of the S–RM increases. When the rock block proportion lies in the range of 25–70%, the increment of the internal friction angle linearly increases with the increment of the rock block proportion. The cohesion of the S–RM decreases compared with that of the soil. When the rock block proportion is larger than 30%, however, there is only a little decrease in the cohesion with the increment of the rock block proportion.     

Antimicrobial effects of selected plant essential oils on the growth of a Pseudomonas putida strain isolated from meat

The inhibitory effect of 60 different essential oils was evaluated on a Pseudomonas putida strain of meat origin, associated with meat spoilage. Essential oils were tested at concentrations from 0.003 to 0.8% (wt/vol) to determine minimum inhibitory and maximal tolerated concentrations (MIC and MTC, respectively) using an agar medium culture. Of the 60 samples tested, Corydothymus capitatus essential oil was the most active showing a MIC of 0.025% and a MTC of 0.06%. Seven essential oils (Cinnamomum cassia, Origanum compactum, Origanum heracleoticum, Satureja hortensis, Satureja montana, Thymus vulgaris carvacroliferum, Thymus vulgaris thymoliferum) have shown a strong antimicrobial activity against P. putida with a MIC of 0.05% and a MTC ranging from 0.013% to 0.025%. Ten other oils (Cinnamomum verum (leaf and bark), Eugenia caryophyllus, Cymbopogon martinii var. motia, Cymbopogon nardus, Melaleuca linariifolia, Origanum majorana, Pimenta dioica, Thymus satureoides, Thymus serpyllum) showed a high antimicrobial activity showing a MIC ranging from 0.1% to 0.4%, while the remaining were less active showing a MIC ? 0.8%.     

有向超图的超网络能量及其性质

图能量表述为方阵形式的矩阵特征值绝对值之和. 网络能量已在无向图、有向图及混合图中得到较为成功的应用,与传统意义上的图能量之间存在多个相同或相似的上下限. 由于图与超图之间的关联,无向图与有向图的网络能量及无向超图的超网络能量之间存在密切联系. 将超网络能量由无向超图推广应用到有向超图,提出了有向超图的超网络能量,分析了无向超图与有向超图的超网络能量之间的关联,同时论述了无向图与有向图的网络能量及无向超图与有向超图的超网络能量之间的联系,最后给出了有向超图的超网络能量若干重要性质.     

Maximal selection in tandem networks with symmetric hearing range

We consider an infinite tandem network in which every node is capable of hearing its neighbors up to a given distancen. At any moment of time every node may contain in the top of its queue a message destined to one of its neighbors. This network can be used as a model for a microwave or optic link with many users. For small and largen we investigate the maximal selection of nodes in the network, for which their transmissions are collision-free. For a large hearing range we show that the upper bound on the maximal selection, which is found herein, is asymptotically achievable. For small hearing ranges we show that a greedy selection is better but not asymptotically optimal. We also specify a sequence of upper bounds which converge to the maximal throughput.This research was done while J. M. Jaffe was on leave at the IBM Israel Scientific Center.     

市区多径衰落信道中的TCM DS／SSMA系统性能分析

本文将网络编码调制（ＴＣＭ）应用于市区多径衰落信道下的直接序列扩频多址（ＤＳ／ＳＳＭＡ）系统中，应用ＤＳ条件下市区多径衰落信道的等效模型，提出了一种采用理论分析和数值模拟相结合分析ＴＣＭＤＳ／ＳＳＭＡ系统在该信道下性能的新方法，并将传统的Ｕｎｇｅｒｂｏｅｃｋ型ＴＣＭ才本文所构成的若干种低码率ＴＣＭＤＳ／ＳＳＭＡ系统的性能进行了比较。