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The influence of synthesis methods on photodegradation efficiency of ZnFe based photocatalysts
No full textOrganic dye pollutants that are progressively used in modern chemical industries, have recently
emerged as a major source of water contamination. Considering the hazardous and
carcinogenic properties of dyes, their removal from water eco-systems is challenging and has
been upgraded to a matter of highest importance. A promising environmentally friendly and
cost-effective approach to water purification is the heterogeneous photocatalytic process that
utilizes various metal oxide semiconductors in the presence of light initiated oxidation-reduction
reactions resulting in dye degradation. The aim of this study was to investigate the influence of
synthesis method on photodegradation efficiency of ZnFe based photocatalysts. The
photocatalysts were synthesized using two different coprecipitation methods: low(LS) and high
(HS) supersaturation The precipitates were thermally treated/activated at 100, 300, 500 and
700℃. Structural and textural characterization was carried out for all prepared samples and
their efficiency in photodegradation of methylene blue (MB) was monitored. Photodegradation
experiments were conducted in an open cylindrical Pyrex reaction vessel containing 100 ml of
test solution (C(MB)=10 mg/l) and 50 mg of powdered photocatalyst. At defined time intervals
aliquots were centrifuged and MB concentrations were determined using UV-VIS
spectrophotometer at 664 nm. Significant difference in photodegradation efficiency among
photocatalysts synthesized by different methods was observed. The study revealed that LS
samples thermally treated at 100°C and 300°C had low photodegradation efficiency, whereas
HS samples thermally treated at same temperatures showed high MB photodegradation
efficiency (65% and 85% after 180 min of UV irradiation). Furthermore, both LS and HS
samples thermally treated at 500°C and 700°C exhibited high photodegradation efficiency, but
the duration of the photodegradation was longer when applying LS samples. The performance
difference in the photodegradation efficiency of LS and HS samples could be explained with
different structural and textural properties triggered by different synthesis methods. ZnFe based
photocatalysts synthesized by both LS and HS methods demonstrated promising photocatalytic
performance indicating their great potential for the application in photocatalytic wastewater
treatment. Nevertheless, HS samples exhibited excellent photodegradation efficiency most
probably due to the optimal properties obtained by the HS synthesis method that played a major
role in tailoring functional properties of ZnFe photocatalysts necessary for the successful MB
photodegradation process
Influence of inter-panel connections on vibration response of CLT floors due to pedestrian-induced loading
No full textLong-span cross-laminated timber (CLT) floors are typically an assembly of prefabricated CLT panels connected together on the site. The actual connections are commonly neglected in design calculations. Hence, a CLT floor is modelled either as a monolith slab or more frequently as a set of CLT panels with no connections at all. This paper presents a numerical study designed to examine the influence of two most common inter-panel connections , i.e. single surface spline and half-lapped joint, on vibration modes and vibration responses of a range of different CLT floors due to pedestrian-induced loading. Although the inter-panel connections are relatively complex in reality, they are modelled here as an equivalent 2D elastic strip between the CLT panels. This relatively simple yet robust model can be used with ease in design practice, regardless finite element (FE) software used to extract vibration modes of a CLT floor. The corresponding monolith floors and floors without inter-panel connections are studied for the comparison of the results. Vertical vibration responses are simulated for low-frequency and high-frequency floors using the corresponding walking force models given in a popular design guideline for footfall induced vibrations of civil engineering structures. Vibration responses were calculated for single pedestrian occupants and their walking paths parallel and perpendicular to the line of connection. The results showed that including the inter-panel connections in a FE model resulted in up to 2.5 higher RMS acceleration levels. Hence, the common practice of modelling CLT floors as monolith slabs or as a set of panels without connections should be left behind
Emerging research on vibration serviceability assessment of pedestrian structures
No full textDespite an increasing number of reported vibration serviceability problems caused by pedestrians walking on newly built footbridges, floors, and staircases around the world, there is still a lack of adequate codes of practice. There are three key issues that a new generation of relevant design guidelines should urgently address: (1) the absence of a universal model that accounts for the entire energy spectrum of walking loading as well as inter-and intra-subject variability of individual walking forces; (2) the effect of human bodies on the dynamic properties of a structure; and (3) pedestrian "intelligent" interaction with the surrounding people and environment. This article provides a brief overview of the relevant state-of-the-art research that has great potential to change this unsatisfactory state of affairs
Integrated design and real-world application of a tuned mass damper (TMD) with displacement constraints for large offshore monopile wind turbines
No full textPassive tuned mass dampers (TMDs) have been increasingly investigated for vibration control of wind turbines. However, TMD designs based on individual or a few operating conditions may result in insufficient consideration of the TMD's impact on wind turbines. For instance, the influence of end-stop collision forces on the main structural damage may be significantly underestimated, thereby affecting the overall lifecycle evaluation. In this study, focusing on large offshore fixed-bottom monopile wind turbines, we propose an integrated TMD design methodology taking the damper displacement constraints into full account. A comprehensive optimization of the passive omnidirectional pendulum-type TMD is conducted considering large number of operating conditions in the offshore environment. Next, a real-world application of the optimally designed TMD is performed for a 6450 kW monopile offshore wind on the Yellow Sea, China. We develop an on-site testing methodology and evaluation criteria for assessing the effectiveness of the TMD offshore. The results of resonance, emergency stop, operatingand reliability test conditions demonstrate the following: under the optimized TMD design taking into account all operating conditions, the TMD with a mass ratio of 1.56% can offer added damping in the fore-aft and side-side directions of the turbine, and provides the desired damping ratio of 1%; within a 4% frequency range around the design frequency, the TMD achieves effective vibration control; at rated power, the TMD achieves a reduction of more than 50% in the amplitude of the tower base side-side bending moment (Mx). The integrated TMD design with displacement constraints allows for the optimal TMD design across all operating conditions, thereby achieving superior overall vibration control and reduction in fatigue loads. The successful real-world application of the TMD based on integrated design methodology is of high value to the research community
Highway Construction Cost Estimation: Identification and Analysis of the Owners’ Perceptions on Cost Drivers
Get PDFHighway construction cost estimates in the early stages of the project can be characterized as quite challenging and risky. Determination of the cost drivers on which the cost estimates are based requires a certain effort (time and money), which makes cost estimates even more challenging. In order to determine the owners' perceptions on the cost drivers from the previously proposed list, an empirical research (questionnaire survey) was conducted where the respondents rated the degree of influence that each cost driver has on highway construction costs and the degree of effort that needs to be invested to establish a cost driver's value. The survey results indicated that owners invest great efforts in the development of project documentation, but also owners' concerns regarding environmental protection issues. Also, they consider contractual cost drivers, such as procurement method, to be very important cost drivers for the highway construction cost estimation
Utilization of solidified industrial hazardous waste in construction: A case study
Get PDFUtilization possibilities of solidified fractions of industrial hazardous waste obtained by mixing
with inert materials in construction were investigated. Waste mineral oils, water-hydrocarbon
emulsions mixture, and waste filter cakes from the physico-chemical treatment of wastewater
generated by washing of patterned rollers for a printing machine, were used as models of
industrial hazardous waste in the solidification process. Investigation comprised preparation of
concrete and asphalt mixtures for further testing. The solidified powder was analyzed regarding
the granulometric composition, while the obtained concrete samples were further subjected
to compressive strength determination, whereas the asphalt mixtures were tested in the
context of potential waterproofing materials. According to the obtained leaching test results,
all the samples met the required conditions for further application. Compressive strength test
results were in the range of 8.7 – 22.6 MPa. Still, the measured compressive strength values
were lower than expected, which is explained using solidified powder fractions of smaller grain
size. According to the results, it can be concluded that the investigated mixtures cannot be used
for structural building elements, but their usage is recommended for elements such as
pavements, roadside, path cubes, concrete haberdashery, etc. Asphalt mixtures showed
acceptable properties in terms of mechanical, durability, and waterproofing tests.Ispitivane su mogućnosti korišćenja solidifikovanih frakcija industrijskog opasnog otpada dobijenog njegovim mešanjem sa inertnim materijalima u građevinarstvu. Kao predstavnici industrijskog opasnog otpada u procesu solidifikacije korišćena su otpadna mineralna ulja, mešavina vodeno-ugljovodonične emulzije i otpadne filter pogačeiz fizičko-hemijskog tretmana otpadnih voda nastalih pranjem dezen valjaka na mašini za štampanje. Istraživanje je podrazumevalo pripremu betona i asfaltne mešavine za dalja ispitivanja. Utvrđen je granulometrijski sastav solidifikovanog praha, uzorci betona su dalje podvrgnuti određivanju čvrstoće na pritisak, a asfaltne mešavine su ispitivane u kontekstu hidroizolacionih materijala. Prema dobijenim rezultatima ispitivanja luženja, svi uzorci su ispunjavali potrebne uslove za dalju primenu. Rezultati ispitivanja čvrstoće na pritisak bili su u opsegu od 8,7 – 22,6 MPa. Izmerene vrednosti čvrstoće na pritisak bile su niže od očekivanih, što se objašnjava upotrebom solidifikovanih frakcija manje granulacije. Na osnovu dobijenih rezultata može se zaključiti da se ispitivane mešavine ne mogu koristiti za konstruktivne građevinske elemente, te se preporučuje njihova upotreba za građevinske elemente kao što su trotoari, ivičnjaci, kocke za staze, betonska galanterija i dr. Asfaltne mešavine su pokazale prihvatljiva svojstva u pogledu mehaničkih, ispitivanja izdržljivosti i hidroizolacije
А practical method for strut-and-tie modelling of the bridge pile cap
Get PDFPile cap is a typical example of a discontinuity region, where the classical beam theory does not apply. Therefore, strut-and-tie (STM) model is considered appropriate for the analysis of pile caps. Although, the strut-and-tie method is a powerful tool, one of its shortcomings is the need for guidelines for the standardized models. Otherwise, it is left to the designer to come up subjectively with the STM model, which is a sensitive task. In literature, usually simple loading (axial compression or compression with bending only in one direction) on a four-pile cap is discussed. In practice, for real bridge structure, usual loading is alternate biaxial bending, along with compression, on much larger number of piles, making the typical four-pile caps models useless. A practical methodology for creating pile cap model with large number of piles and with complex loading is presented step-by-step. It is further illustrated for the cases with six piles and eight piles from the actual bridge structures, where the method was applied in practice
Urban flood protection and stormwater removal: The development of the multifunctional porous pavement prototype
Get PDFSSIMS-Flow: Image velocimetry workbench for open-channel flow rate estimation
No full textImage-based hydrological measurement techniques have surged in popularity over the last decade, with the most common type of data obtained being the open-channel surface velocity field and flow rate. The lack of a feature-rich image velocimetry software often forces practitioners to use multiple tools as part of a cumbersome workflow, which restricts the uptake of such methods and reduces the reproducibility of results. We present the free and open-source software SSIMS-Flow, which handles extraction of video frames, removal of geometric distortions, video stabilization, orthorectification, image enhancement, and velocity and flow rate estimation using the Farnebäck optical flow method improved with specific pooling techniques developed in this study. SSIMS-Flow performance is tested in two case studies and compared with direct reference values and those obtained using industry-standard PIVlab software. In low seeding and tracerless conditions, SSIMS-Flow demonstrates higher velocity estimation accuracy, while delivering several times faster computational runtime
A method for adjusting the shape of semi-oval arches using Hügelschäffer’s construction
Get PDFThere are numerous ways to construct arches as curved structural elements that span openings in architectural buildings. Arches are present in many historical styles, having the role of an identification mark. Contemporary architecture also uses a resource of inherited styles, combining them into an eclectic blend of modern and classic. However, regardless of the aspirations that investors, architects and future users may have towards some of the complex stylistic forms, the question is whether every contractor will be able to meet the set requirements. Although modern construction technology is apt to
perform much more diverse forms than in earlier epochs, there are still situations when some problems, especially geometric ones, need to be solved, since the technology itself has not yet reached the point of its own thinking. One such problem was posed to the authors by a contractor who came up with the question: how to easily and accurately make a template for a semi-oval window arch, with a predefined point (M) through which the arch should pass. Hence, this is not about an elliptical arc for which there are a number of known constructions. The request was to offer a construction of a higher order curve, simple enough to enable quick and easy design and fabrication of templates on the construction site. In semi-oval arcs, the curve deviates from the elliptical one, giving greater curvature at the vertices of the major axis, and lesser at the vertex of the minor semi-axis. To solve this problem, we use the generalization of the Hügelschäffer’s egg curve construction. With input data: the major and minor semiaxes a and b, together with the given position of the point M which defines the deviation of the oval curve from the ellipse, we first determine the displacement of the minor circle of the Hügelschäffer’s construction along the y axis. Then, by applying the transformation of hyperbolism, we obtain the points of the semi-oval. The offered construction gives quick and accurate positions of points on the semi-oval arc, moreover, it allows the adjustment of the shape of the semi-oval arch according to needs (aesthetic, stylistic, constructive, functional, etc.). In the digital age, it is no problem to draw a higher order curve, but in order to simplify the construction for the purpose of making templates on the construction site, we can turn to the classic method - the approximation of curves with circles, as with semi-elliptical arcs. We find the centers of circles and use their successively connected arcs to accomplish the task with synthetic tools: compass and ruler.https://mongeometrija2023.ftn.uns.ac.rs/?page_id=1