Behavior of thin-walled tubes with combined cross-sectional geometries under oblique loading

Hollow tubes are the most important part of any structure because of their load-bearing capacity, lightweight and inexpensive manufacturing cost. One of the methods for improving the performance under quasi-static loading is to vary the cross-sectional shapes. In the real case, structures are seldom subjected to pure axial or pure bending rather they are subjected to a combination of two load cases i.e. oblique loading. In this paper, the circular cross-section was combined with four different polygonal cross-sections namely tetragon, hexagon, octagon and decagon and a total of 13 geometries were obtained. The buckling behavior of each tube was investigated numerically at various angles of inclination. Each tube was modeled in SOLIDWORKS and then was analyzed in ANSYS. Linear buckling code was used for finding the critical load at various angles ranging from 0° to 14°. The overall result was then compared and it was found that the proposed geometry can be a good alternative over conventional circular tubes in terms of load-bearing capacity at angular load

Impact damage resistance and post impact tolerance of optimum banana-pseudo stem fiber reinforced epoxy sandwich structures

Banana fiber has a high potential for use in fiber composite structures due to its promise as a polymer reinforcement. However, it has poor bonding characteristics with the matrixes due to hydrophobic-hydrophilic incompatibility, inconsistency in blending weight ratio, and fiber length instability. In this study, the optimal conditions for a banana/epoxy composite as determined previously were used to fabricate a sandwich structure where carbon/Kevlar twill plies acted as the skins. The structure was evaluated based on two experimental tests: low-velocity impact and compression after impact (CAI) tests. Here, the synthetic fiber including Kevlar, carbon, and glass sandwich structures were also tested for comparison purposes. In general, the results showed a low peak load and larger damage area in the optimal banana/epoxy structures. The impact damage area, as characterized by the dye penetration, increased with increasing impact energy. The optimal banana composite and synthetic fiber systems were proven to offer a similar residual strength and normalized strength when higher impact energies were applied. Delamination and fracture behavior were dominant in the optimal banana structures subjected to CAI testing. Finally, optimization of the compounding parameters of the optimal banana fibers improved the impact and CAI properties of the structure, making them comparable to those of synthetic sandwich composites

Some hematological and biochemical changes in blood serum of Grass carp (Ctenopharyngodon idella) vaccinated with Aeromonas hydrophila following exposure to sublethal concentration of diazinon

.Diazinon is commonly used for pest control in the agricultural fields in north of Iran. This study was conducted to determine the chronic toxicity of organophosphorous pesticide (Diazinon) in vaccinated fish and its effects on some hematological parameters and biochemical blood plasma profiles of Grass Carp (Ctenopharyngodon idella).This experiment was carried out in three groups. The first group was vaccinated and exposed to diazinon (group A) while the second group was vaccinated and bathed with PBS bath (group B). The remaining fish were used as unvaccinated fish and were kept in clean water separately (group C). Diazinon was applied at concentrations of 2 mg/L for 12 hours since the experiments were initiated. The experimental groups(A and B) showed significantly lower values (p < 0.05) of erythrocyte count, haemoglobin content, haematocrit, leucocytes, Lymphocyte, myelocyte and monocyte, as well as in alkaline phosphatases, alanine aminotransferase, aspartate aminotransferase and, lactate dehydrogenase compared to the control group(C). Values of MCV, MCH and MCHC of experimental species (A and B) were compared to the control group(C). The results of examinations of the biochemical blood plasma profile indicate a marked neurotoxic effect of diazinon in fishes. Changes in values of both erythrocyte and leukocyte profile after exposure to diazinon-based preparation may be referred to disruption of haematopoiesis as well as to a decrease on non-specific immunity of the fis

3-(3-Meth­oxy­benzo­yl)-1,1-diphenyl­thio­urea

The thiono and carbonyl groups in the title compound, C21H18N2O2S, adopt an anti disposition with respect to the central C—N bond. The diphenyl­amine rings are twisted relative to each other by a dihedral angle of 82.55 (10)°. The 3-meth­oxy­benzoyl fragment is twisted relative to one of the diphenyl­amine rings, forming a dihedral angle of 74.04 (9)°. In the crystal, pairs of inter­molecular N—H⋯S hydrogen bonds link the mol­ecules into centrosymmetric dimers, forming columns parallel to the a axis

Evaluating potential of diatomite as anti clogging agent for porous asphalt mixture

Clogging is a major problem that occurs throughout the service life of porous asphalt due to the open nature of the mixture itself. Diatomite with characteristic of abrasiveness and porous structure seems to have potential in order to remove the clogging materials that mainly consists of soils. This study aims to investigate the effects of diatomite as anti-clogging agent on the permeability rate and strength of porous asphalt. The porous asphalt samples were prepared using Malaysia aggregate gradation and polymer modified bitumen of PG76 was used as the binder. This study focuses on clay as the clogging material at different concentration. A fixed amount of 0.5 g/L diatomite was applied to the porous asphalt samples as an anti-clogging agent prior to clogging cycles. The permeability test and resilient modulus were then conducted at different clogging concentrations (0.5, 1.0, 1.5 g/L) and cycles, with and without diatomite. It was found that samples with diatomite have a higher permeability rate compared to those without any application of diatomite after a few clogging cycles. As the clogging cycles increase, the clogging materials have trapped and filled up the voids in the porous asphalt samples and increase the resilient modulus result

The thermal characteristics and performance of a ground heat exchanger for tropical climates

This paper presents the thermal characteristics and performance of ground heat exchanger (GHE) based on the mathematical model for tropical climate conditions. The case study is undertaken with the depth of ground, z of 2 m, air inlet temperature of 35 °C, air mass flow rate of 0.02–0.2 kg/s and different sizes of internal pipe diameters (ID). The effectiveness of the GHE is analyzed at 0.8, 0.9 and 0.99. The performance results of the GHE show that the flow rate of 0.02 kg/s gives great fluid temperature (Tf) reduction in the pipe compared with higher flow rates. However, the outlet temperature (Tout) of air at the end of the 25 m length of pipe with different flow rates tend to reach the same point with a maximum difference of only 0.36 °C for the range of the flow rates. Meanwhile, the rates of heat transfer relatively increase as the flow rates increase. Effectiveness of 0.9 has been identified that it is possible and achievable to be obtained with the 25 m length of the pipe. This finding has confirmed that the GHE has a great potential and good performance to be implemented in tropical climate countries

Identifying motivation factors of the participation of local community in tourism industry in National Park, Pahang, Malaysia

This study attempt to identify and elaborate a motivation factors influence participation of local community in tourism industry in Kuala Tahan National Park, Pahang, Malaysia. Using random stratified sampling techniques, a total of 400 respondents were selected from seven villages in Kuala Tahan National Park. A theory of push and pull factor were applied in this study. Results showed that most of the local communities were more motivated by pull factors. The motivation by pull factor is due to reasons this tourism industries offers jobs to local peoples. They realize the tourism activities are one of fastest growing economy in their area and provide an employement in order to augment their socioeconomic

Laboratory investigation of coal bottom ash modified warm mix asphalt

Bottom Ash (BA), a coal combustion by-product, found to be a potential material when used to produce asphalt mixture. However, some of its characteristics make it a questionable material for the surface course. Therefore, this study aims to evaluate the compatibility of BA in Warm Mix Asphalt (WMA) technology through the basic mechanical properties of the asphalt mixtures for binder course layer (AC 28). Two WMA chemical additives, Cecabase RT and Evotherm 3G, were used at the concentrations of 0.3, 0.4 and 0.5% from the binder's weight. The binder properties were assessed through penetration, softening point and viscosity tests. The Marshall mix design was used to determine the optimum binder content (OBC). The additive dosage and production temperature for WMA were determined through Marshall stability, flow, air voids and specific gravity. The results show that the additives did not significantly affect the binder properties, although, at 0.4% Evotherm 3G, a drop of 17.5% in penetration was observed. Cecabase RT produced WMA with promising results but did not enhance the workability of WMA containing bottom ash (BAWMA). By lowering the production temperature of 25 °C, WMA and BAWMA at 0.4 %, Evotherm 3G demonstrated comparable workability to the conventional Hot Mix Asphalt (HMA). The data achieved through this study would be a guiding approach towards the application of BA in WMA technology for sustainable pavements

College students perception on physical education classes during their high school days

This purpose of this study is to identify and investigate whether there are similarities or differences between genders regarding the perceptions on physical activities of college university students in one of the largest University in Kuala Lumpur, Malaysia. The focus was on three main categories, namely general knowledge, physical education and scientific basis of physical activities. Each category contained questions which serve to evaluate their perceptions about physical activities. The questionnaire was adapted from a journal article on a study done by Mowatt, DePauw and Hulac (1988). This study investigates the perceptions of 113 students (55 males; 65 females) aged between 19 and 25 about physical activities, using the above-mentioned categories. Results of the t-test showed significant differences for general knowledge, t(23) = 3.9, p0.05 no significant differences in means were found between the male and female students

Evaluating the performance of reclaimed asphalt pavement incorporating pelletrap as a rejuvenator

In the recent years, the use of reclaimed asphalt pavement (RAP) in the pavement has become inevitable for economic and environmental reasons. However, the brittleness property of aged asphalt in the RAP restrict its usage in a high percentage. Nevertheless, the rejuvenators are introduced into the mixtures to reverse the effect of ageing processes, decrease the stiffness and increase the workability of RAP mixture. In the present research, various percentages of PelletRAP rejuvenator were added to 100% of RAP mixtures. The performance characteristics of rejuvenated mixtures were investigated via resilient modulus (MR), dynamic creep, and wheel tracking tests. The results showed that when the PelletRAP was included into the mixture, the MR values and the creep stiffness modulus (CSM) decreased, while the permanent creep, the creep strain slope (CSS) and the rutting depth increased. However, all the rejuvenated mixtures exhibited better results than that of virgin mixture. Such a trend of findings suggested that PelletRAP can be used as a rejuvenator without a negative effect on the high-temperature performance of asphalt mixtures