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排序方式: 共有92条查询结果,搜索用时 15 毫秒
1.
This paper addresses the one-machine scheduling problem with earliness-tardiness penalties. We propose a new branch-and-bound
algorithm that can solve instances with up to 50 jobs and that can solve problems with even more general non-convex cost functions.
The algorithm is based on the combination of a Lagrangean relaxation of resource constraints and new dominance rules. 相似文献
2.
Belhadj S Derridj A Aigouy T Gers C Gauquelin T Mevy JP 《Microscopy research and technique》2007,70(10):837-846
A comparative analysis was undertaken to conduct a micromorphological study of Pistacia atlantica leaves by comparing different populations grown under different climatic conditions. Leaf epidermis of eight wild populations was investigated under scanning electron microscope. Micromorphological characteristics (epidermis ornament, stomata type, waxes as well as trichomes) of the adaxial and abaxial leaf surfaces were examined. The epidermis ornament varied among populations and leaf surface, the abaxial leaf surface is reticulate with a striate surface. Messaad site shows a smooth uneven surface. The adaxial leaf surface is smooth but several ornamentations can be seen. The leaflet is amphistomatic; the stomata appeared to be slightly sunken. A variety of stomatal types were recorded; actinocytic and anomocytic types are the most frequent. The indumentum consisted of glandular and nonglandular trichomes. Unicellular glandular trichomes are recorded for P. atlantica leaves in this study. Their density is higher in Oued safene site, located at the highest altitude in comparison with the other populations. The wax occurred in all the sites and its pattern varied according to the populations studied, particularly between Berriane and Messaad. The morphological variability exhibited by the eight populations of P. atlantica may be interpreted as relevant to the ecological plasticity and the physiological mechanisms involved are discussed in this report. 相似文献
3.
Polyamide comprises one of the major classes of polymers. Layered silicates (nanofiller) may enhance properties of polyamide-based hybrids even at very low content. Aliphatic polyamides (nylons) have often been chosen for commercial applications because of excellent physical and chemical properties. Aromatic polyamides (aramids) and aliphatic-aromatic polyamides have been predominantly useful as high-performance materials due to stiffness, low density, and low cost. Recently polyamide blends have become an important route to high-performance materials. Binary blends of polyamide/polypropylene, polyamide/polystyrene, polyamide/polymethyl methacrylate, polyamide/polyurethane, and others have been reported for nanocomposite formation with organoclay. However, ternary blend nanocomposite with nanoclays (PA6/mSEBS, PA6/EPDM-g-MA/H-HDPE) is rarely explored. 相似文献
4.
5.
Adsorption of nitrate and monovalent phosphate anions from aqueous solutions on mono, di‐ and tri‐ammonium‐functionalised mesoporous SBA‐15 silica was investigated. The adsorbents were prepared via a post‐synthesis grafting method, using either 3‐aminopropyltrimethoxysilane (N‐silane) or [1‐(2‐aminoethyl)‐3‐aminopropyl]trimethoxysilane (NN‐silane) or 1‐[3‐(trimethoxysilyl)‐propyl]‐diethylenetriamine (NNN‐silane), followed by acidification in HCl solution to convert the attached surface amino groups to positively charged ammonium moieties. The nominal loading of amino moieties on the SBA‐15 surface was varied from 5% to 20% as organoalkoxysilane/silica molar ratio. The adsorption experiments were conducted batchwise at room temperature. Results showed that adsorption capacity increased with increasing the concentration of monoammonium groups on the SBA‐15 adsorbent. Nitrate adsorption capacity increased from 0.34 to 0.66 mmol ${\rm NO}_{3}^{{-} } /{\rm g}$ adsorbent while phosphate adsorption capacity increased from 0.34 to 0.63 mmol ${\rm H}_{2} {\rm PO}_{4}^{{-} } /{\rm g}$ adsorbent when the molar ratio organoalkoxysilane/silica was varied from 5% to 20%, respectively. Also, for the same organoalkoxysilane/silica molar ratio of 10%, the adsorption capacity increased with the increase of the number of protonated amines in the functional groups. Therefore, maximum adsorption capacities of 0.80, 1.16 and 1.38 mmol ${\rm NO}_{3}^{{-} } /{\rm g}$ adsorbent and 0.72, 0.82 and 1.17 mmol ${\rm H}_{2} {\rm PO}_{4}^{{-} } /{\rm g}$ adsorbent were obtained using mono‐, di‐ and triammonium functionalised SBA‐15 adsorbents, respectively. © 2011 Canadian Society for Chemical Engineering 相似文献
6.
This article reviews the research and progress on polystyrene and nanoclay-based nanocomposite. Polystyrene is one of the most extensively used commercial polymers in the world. This review is designed to be an expansive source for polystyrene–clay nanocomposite research, including synthesis, characterization, structure/property relationship, manufacturing techniques, and applications considering thermal, mechanical, barrier, electrical conductivity, non-flammability, and biodegradability. The frequently used clays with polystyrene are montmorillonite, bentonite, hectorite, and kaolinite. The polystyrene–clay nanocomposite has several interesting commercial significances in packaging, automotive, fuel cell, construction, and electrical materials. Finally, future challenges toward the technical applications of these advance materials have been discussed. 相似文献
7.
Interactive voice browsers offer an alternative paradigm that affords ubiquitous mobile access to the WWW using a wide range
of consumer devices. This technology can facilitate a safe, “hands-free” browsing environment that is of importance both to
car drivers and various mobile and technical professionals. This paper describes the challenges of architecting an interactive
voice browser that combines digital audio with the features of a speech synthesizer to make structural elements of the document
explicit to the listener. The aesthetics of the audio rendition can simultaneously help reduce the monotony factor and enhance
comprehension. The evolution of the voice browser gave rise to a new conceptual model of the HTML document structure and its
mapping to a 3D audio space. A number of novel features are discussed for improving both the user’s comprehension of the HTML
document structure and their orientation within it. These factors, in turn, can improve the effectiveness of the browsing
experience. 相似文献
8.
Heterotopic brain tissue, except in the head and neck region, is exceedingly rare. Mature neural tissue unexpectedly found in the subcutaneous tissues of the back of a toddler lacked an attachment to the central nervous system (CNS), and appeared to be unorganized glial tissue on pathologic evaluation. Appropriate clinical management of such lesions includes a suspicion of subcutaneous lesions near the CNS and evaluation to eliminate the presence of communication with the CNS, followed by surgical excision. 相似文献
9.
Arslan Usman M.S. Rafique M. Khaleeq-ur-Rahman K. Siraj Safia Anjum H. Latif Taj M. Khan Mazhar Mehmood 《Materials Chemistry and Physics》2011
The structure and surface morphology of Ni-incorporated diamond like carbon (Ni:DLC) films have been investigated. These films were deposited on Si substrates using pulsed laser deposition (PLD) technique. A KrF Excimer laser (λ = 248 nm) was used for co-ablation from multi component Ni–graphite target. The concentration of Ni was varied by ablating the Ni part of the target with various numbers of laser pulses. The SEM and AFM analysis reveals that the surface is composed of segregates of Ni which increases with the increase in Ni content during the growth process. The structural investigations by XRD and Raman spectroscopy provided information about the orientation of the incorporated constituent and the ordering of the carbon species. Maximum height of the nano structures which were observed on the surface was ∼50 nm. The G-peak of the graphite was shifted towards higher wave number due to enhancement in SP2 sites which have been increased due to the increase in the Ni concentration. A small change in the surface roughness ranging from 7.78 nm to 13.1 nm due to increased Ni concentration was also observed. 相似文献
10.
The introduction of ionic additives, such as KCN, or acidic comonomer units, such as methacrylic acid, which change the nature of the mechanism of nitrile oligomerization reaction from radical to ionic and cause its initiation at lower temperature, allows the level of obscurity and the total amount of smoke production, both in smouldering and flaming conditions to be decreased. An opposite result is obtained if diphenylpicrylhydrayl (DPPH) radicals in polyacrylonitrile is introduced; DPPH retards the initiation of the radical nitrile oligomerization reaction. The acrylonitrile-methacrylic acid copolymers have a limiting oxygen index, which increases with the methacrylic acid content. Owing to the increased amount of NH3 produced during pyrolysis, the copolymers have a swelling behavior during the combustion test. 相似文献