Mixing of Pure Air Jets with a Reacting Fuel-Rich Crossflow

Jets in a crossflow play an integral role in practical combustion systems such as can and annular gas turbine combustors in conventional systems, and the Rich-burn/Quick-mix/Lean-burn (RQL) combustor utilized in stationary applications and proposed for advanced subsonic and supersonic transports. The success of the RQL combustor rests with the performance of the quick-mixing section that bridges the rich and lean zones. The mixing of jet air with a rich crossflow to bring the reaction to completion in the lean zone must be performed rapidly and thoroughly in order to decrease the extent of near-stoichiometric fluid pocket formation. Fluid pockets at near-stoichiometric equivalence ratios are undesirable because the high temperatures attained accelerate pollutant formation kinetics associated with nitric oxide (NO). The present study develops a model experiment designed to reveal the processes that occur when jet air is introduced into hot effluent emanating from a fuel-rich reaction zone

Optimization of Jet Mixing Into a Rich, Reacting Crossflow

Radial jet mixing of pure air into a fuel-rich, reacting crossflow confined to a cylindrical geometry is addressed with a focus on establishing an optimal jet orifice geometry. The purpose of this investigation was to determine the number of round holes that most effectively mixes the jets with the mainstream flow, and thereby minimizes the residence time of near-stoichiometric and unreacted packets. Such a condition might reduce pollutant formation in axially staged, gas turbine combustor systems. Five different configurations consisting of 8, 10, 12, 14, and 18 round holes are reported here. An optimum number of jet orifices is found for a jet-to-mainstream momentum-flux ratio (J) of 57 and a mass-flow ratio (MR) of 2.5. For this condition, the 14-orifice case produces the lowest spatial unmixedness and the most uniformly-distributed species concentrations and temperature profiles at a plane located one duct diameter length from the jet orifice inlet

Synergistic co-cultivation of activated sludge and microalgae in enhancing lipid production and N-laden wastewater treatment

The influence of inoculation ratios of activated sludge and microalgae were investigated in this study in the aspects of biomass yield, lipid yield and total nitrogen (TN) removal efficiency. It was observed that mixed culture of activated sludge/microalgae with the ratio 1:1 and 1:0.75 achieved a maximum lipid production up to 0.144 g/L and 0.133 g/L as compared with microalgae culture alone, which was only 0.081 g/L. The highest total nitrogen (TN) removal was observed with 1:1 and 1:0.75 ratios of activated sludge/microalgae cultures ranging from 96.3-96.9% removal efficiency, which was an improvement of about 90% removal efficiency compared to the activated sludge culture (6.25±0.08%). The flocculation efficiency was generally improved in mixed cultures of activated sludge andmicroalgae in comparison with only activated sludge culture and microalgae culture alone.Keywords: activated sludge; microalgae; co-cultivation; lipid; nitrogen removal

Jet Mixing in a Reacting Cylindrical Crossflow

This paper addresses the mixing of air jets into the hot, fuel-rich products of a gas turbine primary zone. The mixing, as a result, occurs in a reacting environment with chemical conversion and substantial heat release. The geometry is a crossflow confined in a cylindrical duct with side-wall injection of jets issuing from round orifices. A specially designed reactor, operating on propane, presents a uniform mixture without swirl to mixing modules consisting of 8, 9, 10, and 12 holes at a momentum-flux ratio of 57 and a jet-to-mainstream mass-flow ratio of 2.5. Concentrations of O2, CO2, CO, and HC are obtained upstream, downstream, and within the orifice plane. O2 profiles indicate jet penetration while CO2, CO, and HC profiles depict the extent of reaction. Jet penetration is observed to be a function of the number of orifices and is found to affect the mixing in the reacting system. The results demonstrate that one module (the 12-hole) produces near-optimal penetration defined here as a jet penetration closest to the module half-radius, and hence the best uniform mixture at a plane one duct radius from the orifice leading edge

Modeling of the current density distribution under surface posterior-tibial-nerve electric stimulator

Stimulation of the posterior tibial nerve is commonly used in the measurement of somatosensory evoked potential (SEP). To improve the efficiency of stimulation, the potential field and current density distributions under the surface electrodes were modeled and simulated. In our model, three layers were assumed: (1) the air environment, (2) electrode and paste (3) human body (skin and soft tissues). The mirror method was used to analyze the potential field of point charge. Integration of the field and the area of the stimulus gave the potential field of one surface electric pole. The potential field distribution of the bipolar stimulator was obtained by superimposition of two unipolar fields. Finally, the current density distribution was calculated by Laplace equation. The analytical solution of the potential field was found and the numerical solution of the current density distribution calculated. The potential field and current density distributions were simulated by 2-D plot. From the model and simulation, the potential and current density distributions were not found to be uniform under transcutaneous stimulation electrode and the maximum current density is located under the poles. We recommend that bipolar stimulator should be applied axially along the stimulated nerve course.published_or_final_versio

Design and fabrication of 3D-printed anatomically shaped lumbar cage for intervertebra disc (IVD) degeneration treatment

Spinal fusion is the gold standard surgical procedure for degenerative spinal conditions when conservative therapies have been unsuccessful in rehabilitation of patients. Novel strategies are required to improve biocompatibility and osseointegration of traditionally used materials for lumbar cages. Furthermore, new design and technologies are needed to bridge the gap due to the shortage of optimal implant sizes to fill the intervertebral disc defect. Within this context, additive manufacturing technology presents an excellent opportunity to fabricate ergonomic shape medical implants. The goal of this study is to design and manufacture a 3D-printed lumbar cage for lumbar interbody fusion. Optimisations of the proposed implant design and its printing parameters were achieved via in silico analysis. The final construct was characterised via scanning electron microscopy, contact angle, x-ray micro computed tomography (μCT), atomic force microscopy, and compressive test. Preliminary in vitro cell culture tests such as morphological assessment and metabolic activities were performed to access biocompatibility of 3D-printed constructs. Results of in silico analysis provided a useful platform to test preliminary cage design and to find an optimal value of filling density for 3D printing process. Surface characterisation confirmed a uniform coating of nHAp with nanoscale topography. Mechanical evaluation showed mechanical properties of final cage design similar to that of trabecular bone. Preliminary cell culture results showed promising results in terms of cell growth and activity confirming biocompatibility of constructs. Thus for the first time, design optimisation based on computational and experimental analysis combined with the 3D-printing technique for intervertebral fusion cage has been reported in a single study. 3D-printing is a promising technique for medical applications and this study paves the way for future development of customised implants in spinal surgical applications

Composting paper and grass clippings with anaerobically treated palm oil mill effluent

Purpose The purpose of this study is to investigate the composting performance of anaerobically treated palm oil mill effluent (AnPOME) mixed with paper and grass clippings. Methods Composting was conducted using a laboratory scale system for 40 days. Several parameters were determined: temperature, mass reduction, pH, electrical conductivity, colour, zeta potential, phytotoxicity and final compost nutrients. Results The moisture content and compost mass were reduced by 24 and 18 %, respectively. Both final compost pH value and electrical conductivity were found to increase in value. Colour (measured as PtCo) was not suitable as a maturity indicator. The negative zeta potential values decreased from −12.25 to −21.80 mV. The phytotoxicity of the compost mixture was found to decrease in value during the process and the final nutrient value of the compost indicates its suitability as a soil conditioner. Conclusions From this study, we conclude that the addition of paper and grass clippings can be a potential substrate to be composted with anaerobically treated palm oil mill effluent (AnPOME). The final compost produced is suitable for soil conditioner

MICROFRACTURE OF HUMAN THORACOLUMBAR VERTEBRAL BODY UNDER FATIGUE LOADING

The purpose of this study was to investigate the relationship between lumbar vertebral microfracture and fatigue loading on young human spine under physiological cyclic compression loads. Thirty-three thoracolumbar vertebrae (T12 to L4) were obtained from 7 adult Chinese male cadavers. They were randomly divided into 5 groups. Cyclical compression was performed for 20,000 cycles with 2 Hz. Load magnitude was determined respectively as 10%, 20% and 30% of the ultimate compressive load. Four cylindrical sections were obtained from each vertebra and the cross-sectional slides were made. The histomorphometry was used to determine microfracture densitiy and distribution. No fracture was detected in the radiographs of groups III, IV and V after fatigue load. Microfracture density in the cyclic compression group increased from 0.46 #/mm2 in Group III to 0.66 #/mm2 (Group IV) and 0.94 #/mm2 (Group V) under different loading levels (). These results provide evidence for the existence of microfractures caused by fatigue loads that are undetectable by X-ray

Can you trust clinical practice guidelines for laparoscopic surgery? A systematic review of clinical practice guidelines for laparoscopic surgery

BACKGROUND: Clinical practice guidelines aim to support clinicians in providing clinical care and should be supported by evidence. There is currently no information on whether clinical practice guidelines in laparoscopic surgery are supported by evidence. METHODS: We performed a systematic review and identified clinical practice guidelines of laparoscopic surgery published in PubMed and Embase between March 2016 and February 2019. We performed an independent assessment of the strength of recommendation based on the evidence provided by the guideline authors. We used the 'Appraisal of Guidelines for Research & Evaluation II' (AGREE-II) Tool's 'rigour of development', 'clarity of presentation', and 'editorial independence' domains to assess the quality of the guidelines. We performed a mixed-effects generalised linear regression modelling. RESULTS: We retrieved 63 guidelines containing 1905 guideline statements. The median proportion of 'difference in rating' of strength of recommendation between the guideline authors and independent assessment was 33.3% (quartiles: 18.3%, 55.8%). The 'rigour of development' domain score (odds ratio 0.06; 95% confidence intervals 0.01-0.48 per unit increase in rigour score; P value = 0.0071) and whether the strength of recommendation was 'strong' by independent evaluation (odds ratio 0.09 (95% confidence intervals 0.06-0.13; P value < 0.001) were the only determinants of difference in rating between the guideline authors and independent evaluation. CONCLUSION: A considerable proportion of guideline statements in clinical practice guidelines in laparoscopic surgery are not supported by evidence. Guideline authors systematically overrated the strength of the recommendation (i.e., even when the evidence points to weak recommendation, guideline authors made strong recommendations)

Innovation strategies and organisational performance: The moderating role of company size among small- and medium-sized companies

Purpose: Not all innovative ideas or approaches commonly implemented by larger companies apply to smaller firms in all regions. Innovation that does not imply company achievements might exhaust their limited resources and cause the market to be uncompetitive. This paper aims to answer two research questions: (1) Do innovation strategies, such as process, marketing and social innovation, affect the performance of small- and medium-sized enterprises (SMEs)? (2) Does company size moderate the relationship between social and marketing innovations with SMEs' performance? Design/methodology/approach; This paper proposed three innovation strategies (i.e. social, marketing and process innovations) influencing Malaysian SMEs' performance. There were 123 valid respondents from SMEs, and the data were analysed using a structural equation modelling partial least square (SEM-PLS) technique. Findings; The research findings advocate that process innovation directly impacts SMEs' performance, not marketing innovation. Interestingly, the influence of social innovation on organisation performance is only significant when the company size becomes more prominent. Companies can provide consistent and continuous social enhancement that arouses public trust and reputation with more resources and capabilities. Also, smaller companies might concentrate their scarce resources on process innovation with instant beneficial potential instead of a sophisticated marketing strategy. Originality/value; There is limited empirical research examining how different innovation strategies, especially social innovation, affect SMEs' performance in developing countries. Furthermore, the second-generation analysis (PLS-SEM) technique provides more systematic and comprehensive results