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排序方式: 共有340条查询结果,搜索用时 46 毫秒
1.
Diffusers are widely-used to quickly dilute effluents in receiving water bodies. This study proposed a novel diffuser that pre-mixes effluent with ambient water before discharging and that uses the swirling jet to further enhance near-field dilution. The nozzle of the diffuser was examined in two ambient flow conditions: co-flow and counter-flow that are commonly-met in the environment such as oceans due to tidal effect. Physical experiments were first conducted in co-flow on its dilution performance and hydrodynamics, using heated water as the effluent. A 3-D CFD model was developed and calibrated the co-flow scenarios, and then used to investigate the diffuser in counter-flow. The results showed that the nozzle can effectively reduce the maximum temperature rise of the effluent by about 50 % before discharging. The swirling jet from the outlet has a larger shear area, half-width and entrainment rate, enabling the effluent to be rapidly diluted to a minimum of around 10 times at x/D = 6 in co-flow, whereas the dilution for conventional nozzles is about 1 because of the potential core. The flow amplification ratio (α) decreases gradually with increasing velocity ratio in co-flow but increases with increasing velocity ratio in counter-flow. The counter-flow reduces the water drawn into the device; however, the pre-dilution effect at the outlet remains stable. The near-field dilution in counter-flow was significantly enhanced than that in co-flow. Environmental regulations at outfalls and mixing zones can be more easily met using this novel diffuser.  相似文献   
2.
This study compared three representative observational methods for assessing musculoskeletal loadings: Ovako Working Posture Analysis System (OWAS), Rapid Upper Limb Assessment (RULA), and Rapid Entire Body Assessment (REBA). The comparison was based on 209 cases of upper-body musculoskeletal disorders (MSDs) diagnosed by medical doctors. The most awkward/stressful posture in each participant's tasks was assessed using these techniques. Postural loadings were rated more highly by the RULA than by the OWAS and REBA (p < 0.01). The chi-square test and logistic regression analysis showed that only RULA grand score and action level, and REBA action level were associated with MSD work-relatedness (p < 0.01, p < 0.05, and p < 0.05, respectively). The percentage concordant values of the logistic model for the RULA grand score and action level were 52.4% and 44.8%, respectively, while the percentage concordant value for the REBA action level was 22.1%. Therefore, the RULA may be the best system for estimating the postural loads and work-relatedness of MSDs.Relevance to industryWork-related musculoskeletal disorders are the leading cause of workplace disability in the developed countries. For preventing the disorders, quantification of musculoskeletal loads is required.  相似文献   
3.
To minimize the structure distortion and potential de-bonding in adhesive bonding of dissimilar materials (e.g., metals and polymeric composites), a two-component (2 K) low temperature cure modified adhesive consisting of 93.5 wt% commercial Henkel 5089 adhesive, 2.5 wt% N-(2-Hydroxyethyl) ethylenediamine (AEEA) and 4.0 wt% 2-ethyl-4-methylimidazole (2,4-EMI) was formulated. Experimental results showed that the use of the modified adhesive lowered the curing temperature from recommended 177 °C (for 20 min) for Henkel 5089 to 100 °C (for 20 min) or 120 °C (for 10 min) for AA6061-AA6061 joint, and 120 °C (for 20 min) or 130 °C (for 10 min) for AA6061-Cf/PA6 (Nylon 6) and Cf/PA6-Cf/PA6 joints, respectively, due to the faster curing reaction caused by the combined addition of AEEA and 2,4-EMI. It took 5, 3, and 2 days to cure the adhesive-bonded AA6061-AA6061, AA6061-Cf/PA6, and Cf/PA6-Cf/PA6 joints made with the modified adhesive and cured at ambient temperature, respectively. In addition, the modified adhesive had sound working life (5 h) at ambient temperature. The static strengths of all adhesive-bonded AA6061-AA6061, AA6061-Cf/PA6, and Cf/PA6-Cf/PA6 joints with the modified adhesive were hardly affected by thermal exposure cycle (i.e., exposure to 82 °C for 30 min). These results indicated that the modified adhesive possesses the promising characteristics for joining of similar and dissimilar materials.  相似文献   
4.
The purpose of this paper is to examine the role of type of unfamiliarity and information on willingness-to-try unfamiliar healthy native foods in males and females. Specifically, the intuition of “healthy = not tasty” is investigated by probing into the effect of high and low taste expectations in the presence and absence of information on health benefits. Defining Type of unfamiliarity of a dish based on its ingredient and format is a unique contribution of this research. This paper uses a 3 * 2 * 2 full factorial experimental design (Type of unfamiliarity * Health Benefits * Taste Expectations; n = 367). ANCOVA was performed to analyse the quantitative data. Findings suggest that the information on health benefits or taste expectations does not have a main effect on willingness to try a new healthy native food, in both males and females. Type of unfamiliarity does not matter for males but females consider it important to try a new food. Males may possibly be inclined towards choosing healthy foods that set high taste expectations; however, providing information on health benefits may lower their interest levels.  相似文献   
5.
The Food Neophobia Scale (FNS) measures reluctance to try novel foods. In describing foods, the term complexity is not well defined. The objective of this work was to assess the acceptability of familiar and novel foods, with varying levels of flavor complexity in both salty and sweet foods, by food neophobics and neophilics and to assess the effect of expectation (frame-of-reference effect) and familiarity on the acceptability of foods. FNS was administered to 864 subjects, who were classified to neophobic, or neophilic based on their FNS scores. Experiment 1, which was replicated twice, focused on four familiar foods, prepared in two versions, an original version and a more flavorful version. Subjects rated foods on complexity, acceptability and expectation. Neophilics gave significantly higher acceptability ratings to complex foods than bland foods and vice versa for neophobics. The different versions of foods did not always meet panelists’ flavor expectations. Experiment 2 included eight commercial foods, four salty and four sweet, with two novel and two familiar foods used within each taste category/quality. One of the foods within the familiar or novel pairs was expected to be flavorful (e.g. chili is typically served as spicy) and the other expected to be bland. Subjects rated foods on complexity, acceptability, familiarity and expectation. Six out of the eight flavorful versions of foods were chosen by subjects as more complex. Significant factors were taste quality, novelty, expectation, and familiarity (p < 0.05). Overall, neophilics were more accepting of novel foods than neophobics. The significant interaction between expectation and neophobia suggests that neophobics and neophilics may have different expectations of foods. Although neophobia × complexity was not significant, the neophobics’ acceptability ratings for bland versions were higher than for the flavorful versions.  相似文献   
6.
Brominated flame retardants (BFRs) were investigated in juvenile common sole from nursery zones situated along the French coast in 2007, 2008 and 2009. Extensive identification was performed with regard to PBDEs, novel BFRs 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) and decabromodiphenylethane (DBDPE), and other non-PBDE BFRs, namely, hexabromobenzene (HBB) and 2,2′,4,4′,5,5′-hexabromobiphenyl (BB-153). Polybrominated diphenyl ether (PBDE) concentrations (Σ 14 congeners) ranged from 0.01 ng/g to 0.16 ng/g wet weight (ww) in muscle, and 0.07 ng/g to 2.8 ng/g ww in liver. Concentrations were in the lower range of those reported in the literature in other European locations. Lower PBDE concentrations, condition indices and lipid contents were observed in the Seine estuary in 2009, possibly in relation to a lower water flow. The PBDE patterns and ratios we observed suggested that juvenile sole have a relative high metabolic degradation capacity. Non-PBDE BFRs were detected at lower levels than PBDEs, i.e., within the < method detection limit - 0.005 ng/g ww range in muscle, and < method detection limit - 0.2 ng/g ww range in liver. The data obtained is of particular interest for the future monitoring of these compounds in the environment.  相似文献   
7.
Solid phase extraction is widely used in sample pretreatment, concentration and analysis processes due to high selectivity and suitability for low concentration sample system. In this review, we systematically summarized and discussed the development trends of solid phase extraction by bibliometrics method. By analyzing papers output scale, the research and development direction of solid phase extraction technology is prospected. We also give an overview on current strategies of novel solid phase extraction from the separation medium and separation technology. The paper aims to describe the global research profile and the development trends of solid phase extraction, to help researchers to accurately grasp the research trend and to provide support for scientific research institutions to formulate scientific policies and strategic plans. Furthermore, the prospect of the development and application of solid phase extraction is also discussed.  相似文献   
8.
《Ceramics International》2015,41(7):8785-8790
In this study, 3 mol% yttria stabilized zirconia (3YSZ) is investigated as a SOFC electrolyte alternative to 8 mol% yttria stabilized zirconia (8YSZ). The mechanical and electrochemical properties of both materials are compared. The mechanical tests indicate that the thickness of 3YSZ can be reduced to half without sacrificing the strength compared to 8YSZ. By reducing the thickness of 3YSZ from 150 µm to 75 µm, the peak power density is shown to increase by around 80%. The performance is further enhanced by around 22% by designing of novel electrode structure with regular cut-off patterns previously optimized. However, the cell with novel designed 3YSZ electrolyte exhibits 30% lower maximum power density than that of the cell with 150 µm-thick standard 8YSZ electrolyte. Nevertheless, the loss in the performance may be tolerated by decreasing the fabrication cost revealing that 3YSZ electrolyte with cut-off patterns can be employed as SOFC electrolyte alternative to 8YSZ.  相似文献   
9.
Quantitative structure-properties relationship (QSPR) method was used to design some novel antioxidant lubricant additives, while molecular dynamics simulations were used to calculate their dynamic binding energies on steel and to hydrogen-containing DLC (a-C: H) crystal surfaces. 29 synthesized antioxidant lubricant additives were collected from literature and geometrically optimized by Spartan’14 version 1.1.2 software while Genetic Function Algorithm (GFA) method of the material studio version 8.0 software was used to build the predictive QSPR model. Four novel antioxidant lubricant additives were successfully designed out of which E)-3-(4-((3-amino-4-methylphenyl)diazenyl)-5-hydroxy-4H-pyrazol-3-yl)-2-argio-6,7-difluoroquinazolin-4(3H)-one with excellent property of 3.531295 (KOH/g) was found to be better than the one reported by other researchers. The dynamic binding energy results revealed that one of the designed additives was excellently bound to steel (?1120.11 kcal/mol) and to hydrogen-containing DLC (a-C: H) crystals surface (7814.156 kcal/mol) surfaces than its co-additives. This investigation shows that the entire studied antioxidant lubricant additive was found to be better bound to the steel surface than hydrogen-containing DLC (a-C: H) crystals surface. This study will help in synthesizing novel anti-oxidant lubricant additives with better additive properties that will slow the tendency of oil to oxidize and will not possess a threat to the environment as the structures do not contain zinc and phosphorus that could limit the operation of the catalytic converter in the exhaust pipe.  相似文献   
10.
Herein, we report metal catalyzed methanolysis and hydrolysis of hydrazine-borane as a fast hydrogen generation system under mild conditions. To the best of our knowledge, this is the first report that a monodisperse Ru NPs@nano-CeO2 catalyst can achieve a complete conversion of N2H4BH3 to H2 with the assistance of both methanolysis and hydrolysis reactions. In order to achieve hydrolysis and methanolysis effectively, monodisperse Ru NPs@nano-CeO2 catalyst have been prepared by modifying the chemical reduction method which is a very simple and efficient method in room conditions. The synthesized Ru NPs@nano-CeO2 catalyst showed excellent catalytic activity, stability, and selectivity in the production of hydrogen by both hydrolysis and methanolysis of the hydrazine-borane. The results reported here also includes (i) identification of the prepared catalyst by using analytical techniques such as XRD, XPS, TEM, HR-TEM, (ii) determination of stoichiometry for methanolysis and hydrolysis reactions, (iii) determination of rate constants and laws for methanolysis and hydrolysis reactions, (iv) determination of kinetic parameters such as enthalpy, entropy and activation energy for methanolysis and hydrolysis reactions.  相似文献   
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