Fly Ash-based Geopolymer Lightweight Concrete Using Foaming Agent

In this paper, we report the results of our investigation on the possibility of producing foam concrete by using a geopolymer system. Class C fly ash was mixed with an alkaline activator solution (a mixture of sodium silicate and NaOH), and foam was added to the geopolymeric mixture to produce lightweight concrete. The NaOH solution was prepared by dilute NaOH pellets with distilled water. The reactives were mixed to produce a homogeneous mixture, which was placed into a 50 mm mold and cured at two different curing temperatures (60 °C and room temperature), for 24 hours. After the curing process, the strengths of the samples were tested on days 1, 7, and 28. The water absorption, porosity, chemical composition, microstructure, XRD and FTIR analyses were studied. The results showed that the sample which was cured at 60 °C (LW2) produced the maximum compressive strength for all tests, (11.03 MPa, 17.59 MPa, and 18.19 MPa) for days 1, 7, and 28, respectively. Also, the water absorption and porosity of LW2 were reduced by 6.78% and 1.22% after 28 days, respectively. The SEM showed that the LW2 sample had a denser matrix than LW1. This was because LW2 was heat cured, which caused the geopolymerization rate to increase, producing a denser matrix. However for LW1, microcracks were present on the surface, which reduced the compressive strength and increased water absorption and porosity.     

Time and volume-ratio effect on reusable polybenzoxazole nanofiber oil sorption capacity investigated via machine learning

Diesel oil sorption capacities (DOSCs) of polybenzoxazole/polyvinylidene fluoride nanofiber mats with four different groups (-O-, -S-S-, phenylene and diphenylene) in the main chain structures were investigated. Different experimental duration and diesel-oil/tap-water volume ratio pairs were used for diesel oil sorption. No degradation was observed in the nanofiber mat structures after diesel oil sorption. The characterizations of polybenzoxazole (PBO) nanofibers with high diesel oil selectivity were performed by scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, x-ray diffraction, thermal gravimetric analysis, differential scanning calorimetry, Brunauer–Emmett–Teller (BET), and contact angle measurement analysis. According to the result of characterizations, superoleophilic and superhydrophobic nanofiber mats show high water contact angle value in the range of 132–140^∘ and show high separation efficiency. In this study, we integrated ensemble gradient boosting model (XGBoost) to predict the DOSC of sorbent nanofiber and obtain an optimal set of conditions to maximize the DOSC. The predicted PBO-E sorbent at the 0.5 ratio of diesel-oil/tap-water measured at the end of the 3rd minute showed the most reliable and stable diesel oil sorption with at least 9.39 and at most 12.33 g/g sorbent with 95% of confidence.     

Synthesis and biological activity of silyl- and germylsubstituted trifluroacetylfurans

A series of silyl, germyl and alkyl substituted trifluoroacetylfurans has been synthesized under Friedel-Crafts electrophilic acylation conditions. Biological investigations have demonstrated that germyl derivatives of trifluoroacetylfuran are more toxic than the silicon analogues. 5-Triethylgermyl-2- trifluoroacetylfuran was the most toxic compound (CD(nabla), 11.2 mg kg(-1), i.p. for white mice), 200 times more toxic than the silicon analogue. 5-t-Butyl- and 5-trimethylsilyl-2-trifluroacetylfuran prolong the duration of ethanol anaesthesia by 220 and 140%. 5-Triethylgermyl-2-trifluroacetylfuran exibited high anesthetic activity in hexobarbital test (prolonged the duration by 137%). Some of compounds influenced muscle tone and locomotor coordination parameters. 5-Triethylgermyl-2-trifluomacetylfuran exibited analgesic activity (D(nabla), 0.9 mg k}(-infinity)).     

An experimental assessment of module documentation-based testing

Context

Testing a module that has memory using the black-box approach has been found to be expensive and relatively ineffective. Instead, testing without knowledge of the specifications (white-box approach) may not be effective in showing whether a program has been properly implemented as stated in its specifications. We propose instead a grey-box approach called Module Documentation-based Testing or MD-Test, the heart of which is an automatic generation of the test oracle from the external and internal views of the module.

Objective

This paper presents an empirical analysis and comparison of MD-Test against three existing testing tools.

Method

The experiment was conducted using a mutation-testing approach, in two phases that assess the capability of MD-Test in general and its capability of evaluating test results in particular.

Results

The results of the general assessment indicate that MD-Test is more effective than the other three tools under comparison, where it is able to detect all faults. The second phase of the experiment, which is significant to this study, compares the capabilities of MD-Test and JUnit-black using the test evaluation results. Likewise, an analysis of the test evaluation results shows that MD-Test is more effective and efficient, where MD-Test is able to detect at least the same number of faults as, or is at par with, the black-box approach.

Conclusion

It is concluded that test evaluation using grey-box approach is more effective and efficient that the black-box approach when testing a module that has memory.     

天津双口垃圾填埋场垃圾填埋气体收集、发电及清洁发展机制

《京都议定书》中的一项规定允许加入议定书的工业化国家通过从发展中国家的项目中购买排放配额的方式,来完成他们的减排目标。目前中国天津双口垃圾填埋场正在运用清洁发展机制销售认证减排量。西班牙碳基金的托管方世界银行是减排量的购买方。双口垃圾填埋场于2008年夏季开始运营,通过垃圾填埋收集甲烷,继而将其销售给电网用于发电。向电网销售电力的收入可能不足以判断气体收集和电力设备投资的正确性。通过销售甲烷这种全球变暖潜能值较高的温室气体（其全球变暖潜能是二氧化碳的21倍）产生的认证减排量获取的额外收入,对于气体管理体系实现财务上的可持续非常重要。在没有销售排放抵消的情况下,项目的内部收益率是5．87％,而在销售排放抵消时则为15．23％。在内部收益率较低的情况下,项目将不会被运行。该气体管理项目已由天津清洁能源环境工程有限公司（TCEEE）启动,这是由负责管理垃圾填埋场的天津环卫委员会和天津建设管理委员会共同组建的合资公司。世界银行除了托管西班牙碳基金以外,还是另外11家基金会和机构的托管人。TCEEE选择了一家中国公司-南京长期环境技术发展有限公司作为承建拥有运行转让的承包商,以管理垃圾填埋气体收集和电力系统。     

Optical properties and crystallinity of hydrogenated nanocrystalline silicon (nc-Si:H) thin films deposited by rf-PECVD

Hydrogenated nanocrystalline silicon (nc-Si:H) thin films prepared in a home-built radio-frequency (rf) plasma enhanced chemical vapour deposition (PECVD) system have been studied. The rf powers were fixed in the range of 5 W-80 W. The optical properties and crystallinity of the films were studied by X-ray diffraction (XRD), Micro-Raman scattering spectroscopy, high resolution transmission electron microscope (HRTEM), and optical transmission and reflection spectroscopy. The XRD and Micro-Raman scattering spectra were used to investigate the evidence of crystallinity in order to determine the crystallite sizes and crystalline volume fraction in the films. The HRTEM image of the film was used to correlate with the crystallinity that was determined from XRD and Micro-Raman scattering spectra. Optical constants such as refractive index, optical energy gap, Tauc slope, Urbach energy and ionic constants were obtained from the optical transmission and reflectance spectra. From the results, it was interesting to found that the optical constants showed a good correlation with the crystallinity within the variation of rf power. Also, the ionic constants of the films showed an indication of the degree of crystallinity in the films. The variation of the optical energy gap with the rf power based on structure disorder and the quantum confinement effect is discussed.     

Retention and stability of bioactive compounds in functional peach beverage using pasteurization,microwave and ultrasound technologies

Food Science and Biotechnology - The peach functional beverages pasteurized for 10 min at 90 °C, microwaved for 1.5 min at 850 W of power and sonicated for...     

Synthesis of indium-catalyzed Si nanowires by hot-wire chemical vapor deposition

Indium (In) catalyzed silicon nanowires (SiNWs) were synthesized by using hot-wire chemical vapor deposition (HWCVD) technique. Indium droplets were deposited on Si substrates by hot-wire evaporation of In wire, which was immediately followed by the growth of SiNWs from the droplets. Three sets of samples were prepared by varying the length of In wires, l, as 3, 1 and 0.5 mm. The sizes of In catalyst droplets decreased from 271.4 ± 66.8 to 67.4 ± 16.6 nm when the l was reduced from 3 to 0.5 mm. Larger size of In droplets (271.4 ± 66.8 nm) was found to induce the growth of worm-like NWs. The decrease in size of In catalyst droplets induced the formation of aligned and tapered NWs with smaller tips. The smallest value of tapering parameter, T_p of 40.5 nm/μm is correlated to the SiNWs induced by the smallest size of In droplets (67.4 ± 16.6 nm). The as-grown SiNWs showed high purity and good crystalline structure.     

Optical tomography: Image improvement using mixed projection of parallel and fan beam modes

Mixed parallel and fan beam projection is a technique used to increase the quality images. This research focuses on enhancing the image quality in optical tomography. Image quality can be defined by measuring the Peak Signal to Noise Ratio (PSNR) and Normalized Mean Square Error (NMSE) parameters. The findings of this research prove that by combining parallel and fan beam projection, the image quality can be increased by more than 10% in terms of its PSNR value and more than 100% in terms of its NMSE value compared to a single parallel beam.