Epoxy-silicate nanocomposites were prepared by dispersing synthetic layered silicates modified with alkylammonium ions. In the dispersing process, the organically modified layered silicates were mixed in epoxy resin with shearing, and aggregations of the silicates were removed by centrifugal separation after mixing epoxy resin and silicates. Micrographs taken by transmission electron microscopy (TEM) indicate that the nanocomposites have a mixed morphology including both parallel silicate layers (0.1-0.5cun, 5-15 layers) and exfoliated silicate layers (nano-scale dispersion) area. In terms of thermal resistance properties, the glass transition temperature (T,) of the nanocomposite was shifted to a higher temperature (A20OC) than pure epoxy. Furthermore, dispersion of modified silicate prevented relative permittivity (G) and dielectric loss (tans) from increasing at a high temperature above the glass transition temperature. INTRODU CTl ONRecent rapid progress in nanotechnology has stimulated the research and development efforts focused on new high performance materials. In organic-inorganic hybrid materials, many reports have described high performance resins with layered silicates which are nano-dispersed in a polymer matrix (nanocomposites).Nanocomposites realize many improvements, including mechanical and thermal properties, in comparison with pure resin. Nanocomposites using this approach have attracted much interest, since the Toyota research group developed the nylon-layered silicate nanocomposite [l], which was synthesized by the method in which organically modified layered silicate was dispersed and exfoliated in a nylon matrix (Figure 1). This approach was first extended to epoxy resin systems by Pinnavaia et a1 [2], and various studies have been conducted on epoxy-silicate nanocomposites by many researchers [3-51.Epoxy resin has been widely utilized by various industries not only for its superior properties, but also its low cost. In the electrical power industry, we have taken advantage of epoxy resins as insulating and structural materials. Epoxy resin has its properties enhanced by modifying it with inorganic filler or glass fiber to a level that is indispensable for our products (e.g., spacer and FRP rod for gas insulating apparatus (GCB/GIS)). One of the most interesting features of nanocomposites is that improvements to resin properties can be achieved with the addition of a small weight-percentage silicates, therefore, the performance of nanocomposites enables insulating and shvctural materials to have lower weights and volumes. Figure 1 -Preparation method of nanocomposite. Exfoliation and dispersion of organic modified layered silicate occur upon polymerization.To discuss the properties of nanocomposites as insulating and structural materials, we have prepared epoxy-silicate nanocomposites by dispersing synthetic layered silicates modified with alkylammonium ions. The organically modified silicates have an affinity for polymer matrix and would be expected to disperse easily.The preparation metho...
Problem statement: The significance of urban design and planning in the tropics lies mostly on its climatic and regional concerns. Among many design parameters, building height is an important parameter which affects thermal climate in the city considerably. This study investigated the effect of building height on outdoor thermal comfort during the daytime in summer in Dhaka, Bangladesh which is a high density city located in tropical climate zone. This study emphasized on pedestrian comfort condition in a planned residential area in the city. Approach: Thermal comfort was assessed in terms of Temperature-Humidity-Index (THI) which uses air Temperature (T a ) and Relative Humidity (RH). Measurements were carried out in a typical summer day. In addition, to simulate the urban thermal climate, a 3D numerical simulation tool ENVI-met was used. Results: Simulated results showed close agreement with the measured data in case of existing canyon and thus the validity of the present numerical simulation was confirmed. Results showed that in case of existing canyon with average building height of 4-5 storied, THI lies in the discomfort level. A canyon was proposed by increasing the building height to 8-10 storied in the existing canyon. In case of proposed canyon, it was found that increased building height provides comparatively comfortable condition than the existing case during day time. Moreover, mean radiant temperature (T mrt ), surface Temperature (T s ) and wind speed were included in the present study to identify the effects of building height on these factors. Conclusion: The present study had an implication on the urban design process to achieve a more comfortable urban environment by mitigating heat stress in summer.
See video on DCR YouTube Channel at https:// youtu.be/qVWVVrB7_1s BACKGROUND: Total mesorectal excision is the standard surgical procedure for rectal cancer because it is associated with low local recurrence rates. To the best of our knowledge, this is the first study to use an imageguided navigation system with total mesorectal excision. IMPACT OF INNOVATION:The impact of innovation is the development of a deep learning-based imageguided navigation system for areolar tissue in the total mesorectal excision plane. Such a system might be helpful to surgeons because areolar tissue can be used as a landmark for the appropriate dissection plane. TECHNOLOGY, MATERIALS, AND METHODS:This was a single-center experimental feasibility study involving 32 randomly selected patients who had undergone laparoscopic left-sided colorectal resection between 2015 and 2019. Deep learning-based semantic segmentation of areolar tissue in the total mesorectal excision plane
The thermal comfort in urban canyons of a high density city is a very challenging issue for urban planners and designers, especially in hot humid tropical zone. The present study aims to evaluate the effects of a newly promulgated building construction rules in respect of thermal climate for Dhaka, Bangladesh, a region characterized by high density area with tropical climate. Three different urban canyons from three areas were considered which almost represents the whole city. Measurements were carried out to assess the existing thermal climate in the city canyons. Further, three model canyons were configured according to the new rules of ground coverage, floor area ratio (FAR) and site setback. A three-dimensional numerical model with high spatial and temporal resolution was used to investigate the microclimatic changes within the urban environments. Model calculations were run for a typical summer day. The thermal climate was evaluated based on air temperature Ta, surface temperature Ts, relative humidity RH, and wind speed in the existing and model canyons. For thermal comfort assessment the temperature humidity index (THI) was considered in this study. The results showed that the outdoor spaces of the study areas are thermally uncomfortable and the new building construction rules hardly improve the conditions in general. However, THI decreases in a canyon where sky view factor (SVF) decreases in the model canyon than the existing one. In addition, the surface temperature Ts and air temperature Ta do not show the same picture. Furthermore, the wind speed increases in all the model canyons as the site setback allows wind flow uniformly inside the canyons. Keywordssimulation, urban canyon, sky view factor (SVF), thermal climate, air temperature, relative humidity, temperature humidity index (THI)
IntroductionDisadvantages of bowel perfusion assessment with indocyanine green fluorescence angiography include the need for a fluorophore and the subjective nature of the assessment. This study was performed to evaluate the clinical efficacy of bowel perfusion assessment using laser speckle contrast imaging (LSCI) during laparoscopic colorectal surgery.MethodsThe study population comprised the first 27 consecutive patients who underwent laparoscopic left‐sided colorectal resection with intraoperative perfusion assessment using LSCI. The operative outcomes of these patients were compared with those of a matched group of patients without perfusion assessment. We analyzed the flux data expressed in laser speckle perfusion units.ResultsAfter propensity score matching, we found no significant between‐group differences in the patients' characteristics with the exception of the cancer stage. No patients undergoing LSCI perfusion assessment developed anastomotic leakage, but five (18.5%) patients in the control group did, at a significantly higher rate in male patients (P = .042). There were no significant differences in other operative outcomes. The laser speckle perfusion unit values after ligating marginal vessels were significantly lower than before ligation (P < .01).ConclusionsWith respect to anastomotic leakage, LSCI may improve patient outcomes after colorectal surgery. This technique appears to be a superior tool with the advantages of measurement repeatability and quantitativity and no need for a fluorophore.
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