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1.
Sir James Lighthill 《Journal of Engineering Mathematics》1996,30(1-2):35-78
Helical distributions of stokeslets can valuably model microbial locomotion through a fluid, and also the flow field generated, wherever a flagellum actively executes helical undulations (as in many single-celled algae and protozoa) or where (as in many bacteria) the action of rotary motors causes a passive structure of helical shape (which may be a flagellum or else the cell body itself) to rotate. Here, previous biomechanical studies of such modes of locomotion are extended to include analyses of three-dimensional flow fields. In some cases, a rotlet field (curl of a stokeslet) needs to be incorporated in the models. For example, spirochete swimming is modelled by combined helical distributions of stokeslets and rotlets; the computed flow field being confined to within distances of less than twice the radius of the cell body's helical shape from its axis, while including a powerful jet-like interior flow through the coils of the swimming spirochete. 相似文献
2.
Anodic oxidation of mecoprop herbicide at lead dioxide 总被引:1,自引:0,他引:1
The electrochemical oxidation of an aqueous solution containing mecoprop (2-(2-methyl-4-chlorophenoxy)propionic acid) has
been studied at PbO2 anodes by cyclic voltammetry and bulk electrolysis. The influence of current density, hydrodynamic conditions, temperature
and pH on the degradation rate and current efficiency is reported. The results obtained show that the use of PbO2 leads to total mineralization of mecoprop due to the production of oxidant hydroxyl radical electrogenerated from water discharge.
The current efficiency for the electro-oxidation of mecoprop is enhanced by low current density, high recycle flow-rates and
high temperature. In contrast, the pH effect was not significant. It has also been observed that mecoprop decay kinetics follows
a pseudo-first-order reaction and the rate constant increases with rising current density. 相似文献
3.
Ilkka Kuorinka Hannu Alaranta Ilkka Erich 《International Journal of Industrial Ergonomics》1995,15(6):437-446
During the years 1986–1989 The Finnish Work Environment Fund initiated a multicenter, intervention study (programme) to prevent musculoskeletal disorders at work. The programme consisted of four different projects comprising methodological, epidemiological, and interventive themes. The main results were as follows: (1) More than half of the occupational physiotherapists and physicians involved in the project felt that they did not have adequate training for testing the performance capacity of the musculoskeletal system. Several of the most commonly used musculoskeletal tests had either poor validity in predicting future musculoskeletal troubles or had poor reliability. (2) A controlled intervention study showed that active training of neck-shoulder muscles can prevent musculoskeletal troubles, even more than ergonomic actions. (3) It is possible to reduce sick-leave due to low-back disorders by intervention measures directed toward both the work (environment, tools) and the workers (working methods, positive attitude to work, preparedness to keep fit). (4) The identification of ergonomic hazards with the help of teamwork proved to be feasible. The practical improvements, however, were difficult to implement in the prevailing conditions. Some of the improvements increased the work load and the stress of the workers. This aspect needs further consideration. 相似文献
4.
Panjian Li Ilkka Kangasniemi Klaas de Groot Tadashi Kokubo 《Journal of the American Ceramic Society》1994,77(5):1307-1312
Gel-derived titania coating on commercial pure (c.p.) titanium induces hydroxyapatite formation onto its surface from a simulated body fluid (SBF, a metastable calcium phosphate solution). The induced apatite is similar to bone apatite in that it is poorly crystallized, calcium-deficient, and carbonate-containing. Furthermore, the carbonate (CO2–3 ) groups go into the apatite lattice and lie at the positions of PO3–4 and OH– to replace these ionic groups, resembling the (CO2–3 ) groups of bone apatite. Therefore, the apatite induced by the gel-derived titania is said to be bonelike. A chemical stimulation, stemming from abundant hydroxyl groups and negative charges at the surface of the titania gel, is believed to be responsible for the bonelike apatite induction. The potential of bone-bonding is predicted for the gel-derived titania, for it is an efficient bonelike apatite inducer in the SBF. 相似文献
5.
Positional isomers (1-butyryl-2X-3Y-rac-glycerol and 2-butyryl-1X-3Y-rac-glycerol;X,Y=long-chain acyls) of saturated triacylglycerols (TAG) with 34 and 40 acyl carbons were shown to separate in two chromatographic
peaks on immobilized phenyl(65%) methylsilicone column by gas-liquid chromatography, and on reversed-phase ODS-1 column by
high-performance liquid chromatography. The analysis of 500-MHz1H nuclear magnetic resonance (NMR) spectra showed distinct differences between 2-butyryl-1X-3Y-rac-glycerol and 1-butyryl-2X-3Y-rac-glycerol isomers in the resonance signals of methylene and methine protons of glycerol backbone, and carbon-2 methylene of
acyl groups, and methyl protons of butyryl group. The1H NMR spectra of three interesterified mixtures of three monoacid TAG containing saturated butyrate and caproate TAG and unsaturated
butyrate TAG showed that triplets of methyl protons of butyryl groups atsn-1(3)- andsn-2-positions in saturated and unsaturated TAG had similar chemical shifts and that the chemical shift of caproyl methyl protons
was different from those of butyryl methyl protons. The positional distribution of butyryl groups in isolated positional isomers
of butyrate TAG, interesterified TAG mixtures, and natural and interesterified butteroil can be determined by integration
of these signals. 相似文献
6.
We explore the appropriation of a self-management administrative system from the perspective of diagnostic reasoning. The case study, based on documents, ethnography and videotapes, concerns the appropriation of a travel management system in a major university in Finland. To explore this process from a user-centric view, we focus on the diagnostic work required in the appropriation of the new system, analyzing both the generic diagnostic reasoning of how the users navigate in the system and their individual and collaborative problem-solving strategies. This approach reveals the interaction between the users and the technology, which incorporates inbuilt models of users, administrative work and work processes. Our analysis concerns interactive instances which resulted from misdiagnosis of the functions of the system. For example, the orchestration and labeling of items in the application pose diagnostic challenges to end-users and may eventually be resolved in collaboration with administrative personnel. The individual and collaborative diagnostic reasoning sheds light on the hidden organizational embeddedness of self-management solutions, providing suggestions for developing the design and deployment of administrative self-management systems. The appropriated self-management system should finally be based on the end-user’s diagnostic reasoning so that the employees can base their actions on their taken-for-granted competence and the skills gained during the appropriation of the system. 相似文献
7.
Heikki Ailisto Lauri Pohjanheimo Pasi Välkkynen Esko Strömmer Timo Tuomisto Ilkka Korhonen 《Personal and Ubiquitous Computing》2006,10(6):333-344
The prevalent visions of ambient intelligence emphasise natural interaction between user and functions and services embedded in the environment or available through mobile devices. In these scenarios the physical and virtual worlds seamlessly gear into each other, making crossing the border between these worlds natural or even invisible to the user. The bottleneck in reaching these scenarios appear in the natural mapping between the physical objects and their virtual counterparts. The emergence of local connectivity in mobile devices opens possibilities for implementing novel user interface paradigms to enhance this mapping. We present physical selection paradigm for implementing an intuitive human technology interaction for mobile devices. In order to demonstrate the feasibility of the paradigm we implemented two experimental set-ups using commercially available smart phones with IrDA connectivity. The experiments involved selecting a website by physically pointing at its symbol and making a phone call by pointing at an icon representing the person to be called. In tentative user experiments the physical selection method was more time-efficient and it was perceived more positively by the users than a conventional method.
相似文献
Heikki AilistoEmail: |
8.
Although the review process is defined in an extremely formal way, each company normally has its own way of tailoring it, because staff tend to see formal reviews as too heavy a method for practical software development. These tailored versions differ in type and in the grade of formality. This paper introduces some easy ways to improve the review process. The goal is to find steps which are simple enough for the management and staff to accept and efficient enough to improve the review process. 相似文献
9.
This paper is to investigate the unique impact of simulation time-resolutions on energy matching between on-site micro-wind turbine and household electric demand. The focused indices are on-site electrical energy fraction (OEFe), on-site electrical energy matching (OEMe), and their errors (eOEF and eOEM). The methodology consists of parametric analyses with respect to time-resolution levels, averaging methods, demand profiles, turbine capacities, and wind conditions. Two averaging methods are used: ‘Speed Averaging’ and ‘Power Averaging’. With a coarser resolution, two averaging effects have been found. One is an overestimation effect by both the averaging methods, which are more likely to be encountered especially when a high-resolution generation curve frequently crosses intermittent long spikes of a demand curve. The other effect is an underestimation effect on OEFe simultaneously occurring with the Speed Averaging Method under the conditions of (1) a low wind speed and (2) a high unstable wind speed and a low turbine capacity. 相似文献
10.
Keijo Heljanko Misa Keinänen Martin Lange Ilkka Niemelä 《Journal of Computer and System Sciences》2012,78(2):430-440
This paper presents a reduction from the problem of solving parity games to the satisfiability problem in propositional logic (SAT). The reduction is done in two stages, first into difference logic, i.e. SAT combined with the theory of integer differences, an instance of the SAT modulo theories (SMT) framework. In the second stage the integer variables and constraints of the difference logic encoding are replaced with a set of Boolean variables and constraints on them, giving rise to a pure SAT encoding of the problem. The reduction uses Jurdziński?s characterisation of winning strategies via progress measures. The reduction is motivated by the success of SAT solvers in symbolic verification, bounded model checking in particular. The paper reports on prototype implementations of the reductions and presents some experimental results. 相似文献