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排序方式: 共有197条查询结果,搜索用时 15 毫秒
191.
气相色谱-串联质谱法结合QuEChERS方法快速检测软包装饮料中8种光引发剂 总被引:4,自引:0,他引:4
建立了QuEChERS-气相色谱-串联质谱法快速检测软包装饮料(橙汁、苹果汁、桃汁、菠萝汁和凉茶)中8种光引发剂残留的分析方法。样品以乙腈快速提取,NaCl和无水MgSO4除水后,经N-丙基乙二胺(PSA)和C18粉末净化,用气相色谱-串联质谱(GC-MS/MS)分析,采用多反应监测(MRM)模式检测。在0.01,0.1和0.5 mg/kg的添加水平下,5种软包装饮料的平均回收率为60.4%~99.1%;相对标准偏差(RSD)为1.2%~15.9%;检出限(LOD)为0.2~0.8μg/L。结果表明:本方法简便、快速、安全、价格低廉,重现性良好,可用于软包装饮料中多种光引发剂残留的快速确证检测。 相似文献
192.
Mixed-integer rounding (MIR) inequalities play a central role in the development of strong cutting planes for mixed-integer
programs. In this paper, we investigate how known MIR inequalities can be combined in order to generate new strong valid inequalities.?Given
a mixed-integer region S and a collection of valid “base” mixed-integer inequalities, we develop a procedure for generating new valid inequalities
for S. The starting point of our procedure is to consider the MIR inequalities related with the base inequalities. For any subset
of these MIR inequalities, we generate two new inequalities by combining or “mixing” them. We show that the new inequalities
are strong in the sense that they fully describe the convex hull of a special mixed-integer region associated with the base
inequalities.?We discuss how the mixing procedure can be used to obtain new classes of strong valid inequalities for various
mixed-integer programming problems. In particular, we present examples for production planning, capacitated facility location,
capacitated network design, and multiple knapsack problems. We also present preliminary computational results using the mixing
procedure to tighten the formulation of some difficult integer programs. Finally we study some extensions of this mixing procedure.
Received: April 1998 / Accepted: January 2001?Published online April 12, 2001 相似文献
193.
Hiroshi Nagamochi Toru Hasunuma 《Journal of Algorithms in Cognition, Informatics and Logic》2001,38(2)
We present an efficient
algorithm for finding a sparse k-edge-connectivity certificate of a multigraph G. Our algorithm runs in O((log kn)(log k)2(log n)2) time using O(k(n + m′)) processors on an ARBITRARY CRCW PRAM, where n and m′ stand for the numbers of vertices in G and edges in the simplified graph of G, respectively. 相似文献
194.
Classical cuts for mixed-integer programming and branch-and-cut 总被引:1,自引:0,他引:1
Manfred Padberg 《Mathematical Methods of Operations Research》2001,53(2):173-203
195.
Hiroshi Nagamochi Toshihide Ibaraki 《Journal of Algorithms in Cognition, Informatics and Logic》1999,30(2):253
For a given undirected graphG = (V, E, cG) with edges weighted by nonnegative realscG:E → R + , let ΛG(k) stand for the minimum amount of weights which needs to be added to makeG k-edge-connected, and letG*(k) be the resulting graph obtained fromG. This paper first shows that function ΛGover the entire rangek [0, +∞] can be computed inO(nm + n2 log n) time, and then shows that allG*(k) in the entire range can be obtained fromO(n log n) weighted cycles, and such cycles can be computed inO(nm + n2 log n) time, wherenandmare the numbers of vertices and edges, respectively. 相似文献
196.
For an edge-weighted graph G with n vertices and m edges, we present a new deterministic algorithm for computing a minimum k-way cut for k=3,4. The algorithm runs in O(n
k-1
F(n,m))=O(mn
k
log(n
2
/m)) time and O(n
2) space for k=3,4, where F(n,m) denotes the time bound required to solve the maximum flow problem in G. The bound for k=3 matches the current best deterministic bound ?(mn
3) for weighted graphs, but improves the bound ?(mn
3) to O(n
2
F(n,m))=O(min{mn
8/3,m
3/2
n
2}) for unweighted graphs. The bound ?(mn
4) for k=4 improves the previous best randomized bound ?(n
6) (for m=o(n
2)). The algorithm is then generalized to the problem of finding a minimum 3-way cut in a symmetric submodular system.
Received: April 1999 / Accepted: February 2000?Published online August 18, 2000 相似文献
197.