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941.
This paper addresses a field technician scheduling problem faced by many service providers in telecommunication industry. The problem is to assign a set of jobs, at different locations with time windows, to a group of field technicians with different job skills. Such a problem can be viewed as a generalization of the well-known vehicle routing problem with time windows since technician skills need to be matched with job types. We designed and tested several heuristic procedures for solving the problem, namely a greedy heuristic, a local search algorithm, and a greedy randomized adaptive search procedure (GRASP). Our computational results indicate that GRASP is the most effective among them but requires more CPU time. However, the unique structure of GRASP allows us to exploit parallelism to achieve linear speed-up with respect to the number of machines used. 相似文献
942.
Pascal Auscher Steve Hofmann Alan McIntosh Philippe Tchamitchian 《Journal of Evolution Equations》2001,1(4):361-385
We prove the Kato conjecture for elliptic operators and N×N-systems in divergence form of arbitrary order 2m on . More precisely, we assume the coefficients to be bounded measurable and the ellipticity is taken in the sense of a G?rding
inequality. We identify the domain of their square roots as the natural Sobolev space . We also make some remarks on the relation between various ellipticity conditions and G?rding inequality.
Received May 4, 2001; accepted September 6, 2001. 相似文献
943.
We report on the fabrication and testing of planar nib-like structures for nanoelectrospray ionization-mass spectrometry (nanoESI-MS) applications. The micro-nib structures were fabricated on silicon substrates using the negative photoresist SU-8; they include capillary slots with widths of 8 and 16 microm. A suitable wafer cleaving step made the nib-like structures overhang the edge of a silicon substrate to provide a robust interface for nanoESI-MS applications; this freeing of the nib tip from the wafer surface created a point-like structure that is essential to establish an electrospray. The micro-nib sources were successfully tested on an LCQ Deca XP+ ion trap mass spectrometer using peptide samples at concentrations down to 1 microM. The high voltage was applied using a platinum wire inserted in the sample reservoir upstream to the capillary slot. A Taylor cone was clearly seen at the nib tip. The micro-nibs performed well at voltages as low as 0.8 kV; such performances are state-of-the-art with respect to current micromachined ESI-MS interfaces and are conditions comparable to those used for standard emitter tips. In addition, we clearly observed the influence of the micro-nib slot width on the ionization performances: the narrower the slot, the better the performances. 相似文献
944.
945.
In the chitons (Polyplacophora, Mollusca), the body is not entirely protected by the shell. Mineralized spicules or scales often, but not always, decorate the exposed part of the girdle. Here, we report a study on the composition and ultrastructural organization of these mineralized skeletal parts in four different chiton species. In all specimens, the mineral component (97–98 wt‐%) is aragonite, and the organic matrix (2–3 wt‐%) consists of highly glycosylated proteins. X‐Ray diffraction and scanning electron microscopy show that the organic matrix fibers are aligned, morphologically and crystallographically, with the prismatic aragonite crystals. Matrix and mineral are thus clearly related. The matrix–mineral composite bundles are, however, assembled in the various skeletal parts examined with widely different degrees of alignment and order. In the same organism, the crystals are aligned within a range of ±15° in one type of spicule, while they are randomly oriented in another type. The wide heterogeneity in shape, density, and ultrastructure suggests that the girdle mineralized tissues do not fulfill a fundamental role necessary for the survival of the organism. This, together with the lack of chitin in the organic matrix, supports the hypothesis that they evolved separately from the other chiton mineralized tissues, namely the shell plates and teeth. 相似文献
946.
The separation and detection of volatile organometallic compounds containing tin, iron, and nickel has been achieved using capillary GC–inductively coupled plasma–mass spectrometry (capillary GC-ICP-MS). Detection limits range from 3.0 to 7.0 pg/s. The presence of volatile organotin compounds in a harbor sediment has been confirmed. The retention range of the organometallic compounds analyzed by capillary GC-ICP-MS has been extended considerably beyond that possible in earlier studies (retention indices up to 3400). 相似文献
947.
Jaephil Cho Steve W. Martin Benjamin Meyer Kyung-Han Kim David R. Torgeson 《Journal of Non》2000,270(1-3):205-214
The 11B NMR spectra of xRb2S+(1−x)B2S3 glasses in the range 0x0.75 and of xCs2S+(1−x)B2S3 glasses in the range 0x0.60 are reported. The addition of Rb2S to B2S3 creates on average approximately two and one-half tetrahedral borons for each added sulfur ion, whereas it is found that the addition of Cs2S creates approximately 2 tetrahedral borons for each added sulfur ion. This behavior while more similar to that seen in the alkali borate glasses, contrasts that seen in the Na and K thioborate glasses, where six to eight and three, respectively, tetrahedral borons are formed for every sulfide anion added to the glass. These findings are supported by the IR and 11B NMR spectra of the di-thioborate polycrystals (c-Rb2S:2B2S3 and c-Cs2S:2B2S3) whose structures appear to be comprised of two BS4 tetrahedrals and two BS3 trigonals (N40.5) like that in the alkali di-borate phases for both Rb and Cs. Unlike the 11B NMR resonances of the sodium thioborate glasses where a single sharp line is observed for the tetrahedral boron site and a single quadrupolar broadened line is observed for all the trigonal sites, a third resonance line is observed at high alkali fractions for the rubidium and cesium thioborate glasses. This new structural feature may arise from asymmetric MBS2 (meta-thioborate groups) or tetrahedral boron groups possessing a non-bridging sulfur. 相似文献
948.
949.
950.