排序方式: 共有12条查询结果,搜索用时 15 毫秒
1.
Jong Sam Jeon 《Linear algebra and its applications》2011,435(5):1147-1156
Let A be an n×n irreducible ray or sign pattern matrix. If A is a sign pattern, it is shown that either A is powerful or else Ak has an ambiguous entry for some , and further, sign patterns based on the Wielandt graph show that this bound is the best possible. If A is a ray pattern, partial results for the same bound are given. 相似文献
2.
Previous studies in the issue of inventory models with imperfect quality assumed the defectives could be sold in a batch by the end of the inspection process and the manufacturing systems were push systems. However, the above assumptions may not be true in the pull system in which buyer is powerful. Therefore, in this paper, we develop a new inventory model for items with imperfect quality and quantity discounts where buyer has exerted power over its supplier. Based on the concept of powerful buyer, there are three considerations included in this new model: (1) the order quantity is manufactured at one setup and is shipped over multiple deliveries, (2) the defectives are screened out by a 100% inspection for each shipment but sold in a batch by the end of inspection at the last shipment of each cycle, and (3) the supplier offers quantity discounts to response the request of the powerful buyer. Further, an algorithm is developed to help the powerful buyer to determine the optimal order policy accurately and quickly. Two numerical examples are available in this paper to illustrate the proposed model and algorithm. Besides, based on the numerical examples, a sensitivity analysis is made to investigate the effects of four important parameters (the inspection rate, the defective rate, the receiving cost, and the ordering cost) on the optimal solution. 相似文献
3.
Primož Moravec 《代数通讯》2013,41(11):4096-4119
We study powerful 2-Engel groups. We show that every powerful 2-Engel group generated by three elements is nilpotent of class at most two. Surprisingly, the result does not hold when the number of generators is larger than three. In this article and its sequel, we classify powerful 2-Engel groups of class 3 that are minimal in the sense that every proper powerful section is nilpotent of class at most 2. 相似文献
4.
Vladimir O. Abramov Marat S. Mullakaev Anna V. Abramova Igor B. Esipov Timothy J. Mason 《Ultrasonics sonochemistry》2013,20(5):1289-1295
A new method for the ultrasonic enhancement of oil recovery from failing wells is described. The technology involves lowering a source of power ultrasound to the bottom of the well either for a short treatment before removal or as a permanent placement for intermittent use. In wells where the permeability is above 20 mD and the porosity is greater than 15% ultrasonic treatment can increase oil production by up to 50% and in some cases even more. For wells of lower permeability and porosity ultrasonic treatment alone is less successful but high production rates can be achieved when ultrasound is applied in conjunction with chemicals. An average productivity increase of nearly 3 fold can be achieved for this type of production well using the combined ultrasound with chemical treatment technology. 相似文献
5.
Local bases of primitive non-powerful signed digraphs 总被引:3,自引:0,他引:3
In 1994, Z. Li, F. Hall and C. Eschenbach extended the concept of the index of convergence from nonnegative matrices to powerful sign pattern matrices. Recently, Jiayu Shao and Lihua You studied the bases of non-powerful irreducible sign pattern matrices. In this paper, the local bases, which are generalizations of the base, of primitive non-powerful signed digraphs are introduced, and sharp bounds for local bases of primitive non-powerful signed digraphs are obtained. Furthermore, extremal digraphs are described. 相似文献
6.
Robert C. Brigham Teresa W. Haynes Stephen T. Hedetniemi 《Discrete Mathematics》2009,309(8):2140-2147
For a graph G=(V,E), a non-empty set S⊆V is a defensive alliance if for every vertex v in S, v has at most one more neighbor in V−S than it has in S, and S is an offensive alliance if for every v∈V−S that has a neighbor in S, v has more neighbors in S than in V−S. A powerful alliance is both defensive and offensive. We initiate the study of powerful alliances in graphs. 相似文献
7.
For environmental analyses, a high-performance and powerful preconcentration system exceeding 1×107-fold was developed that was composed of a blue cotton method (solid extraction method)/homogeneous liquid–liquid extraction method/on-line concentration method for capillary electrophoresis (CE). This system was named the “triplex concentration system” and it was achieved by finding a new phase-separation phenomenon (homogeneous liquid–liquid extraction) from a water-miscible organic solvent. Parts per trillion levels of polycyclic aromatic hydrocarbons (PAHs) were used as model analytical targets in this study. With the proposed method, 20-L levels of environmental water could be preconcentrated up to 1×107-fold within a maximum of 1 h. The parts per trillion levels of PAHs were easily determined even using UV/CE, which has a serious sensitivity problem, and the detection limit of benzo[a]pyrene was 3.60 ppt. This system was also used as a practical monitoring method for the Miyata River (in Japan). 相似文献
8.
Jon González-Sánchez 《代数通讯》2013,41(12):4476-4488
In this text, we study Kirillov's orbit method in the context of Lazard's p-saturable groups when p is an odd prime. Using this approach we prove that the orbit method works in the following cases: torsion free p-adic analytic pro-p groups of dimension smaller than p, pro-p Sylow subgroups of classical groups over ? p of small dimension and for certain families of finite p-groups. 相似文献
9.
Based on a series of recent papers, a powerful algorithm is reformulated for computing the maximal eigenpair of self-adjoint complex tridiagonal matrices. In parallel, the same problem in a particular case for computing the sub-maximal eigenpair is also introduced. The key ideas for each critical improvement are explained. To illustrate the present algorithm and compare it with the related algorithms, more than 10 examples are included. 相似文献
10.
《代数通讯》2013,41(7):3497-3504
Abstract In this paper,we present a sharp bound for the nilpotency class of a finite p-group (where p is an odd prime) in terms of its coexponent. As to a powerful p-group,we give the sharp bound for the nilpotency class in terms of its coexponent for arbitrary prime p. 相似文献