Provide Strategies for Elevating the Level of Creativity of University Students in the Educational System

Students are future owners and operators that kept in line that we should be modeled for them in the period of study, and lead them on a path of excellence. Because enhance creativeness and motivation in students and teachers is a key to improve the quality of engineering education. One of the necessities of teaching is deep learning and viable understanding that effect of creates interest and motivation to learn lessons in students. Most students take a course for passing look and they are not interested in it, since they have trouble in learning courses. Teaching methods satisfy all the needs of learning and motivation and interest in the students plays a significant role. This paper describes the concept of creativity. Then several factors studied in the development of intellectual studen

Polymer-based Piezoelectric Material and Device for Energy Harvesting and Sensing in Civil Infrastructure

Recent studies on piezoelectric materials have resulted in the development of a wide verity of piezoelectric devices such as nanogenerators and sensors. This technology is prevalently dominated by the ceramic materials which are brittle and have a very limited strain level. Moreover, despite a wide working frequency range, the ceramic-based piezoelectric devices can only work under tiny forces to avoid damage to the device. As such, due to inherent brittleness, the piezoelectric technology has not been widely explored in civil engineering applications due to the aforementioned drawbacks of ceramic materials. This thesis aims to develop an efficient piezoelectric polyvinylidene fluoride (PVDF) nanofiber device which can be used in both energy harvesting and sensing civil infrastructure applications. The β-phase of PVDF is responsible for its electroactive properties such as ferroelectric, piezoelectric and pyroelectric properties. In spite of several efforts to improve the β-phase content, it is still a challenge to fabricate a PVDF sensor with high efficiency due to the complication of the required post-treatment process which mainly includes electrical poling and mechanical stretching. The electrospinning method was used in this study to synthesize the cost-effective and large-scale piezoelectric nanofiber composite, making it feasible for commercial, industrial and civil engineering applications. The process-structure-property relations of electrospun PVDF nanofiber has been systematically studied. As a result, a reliable model was developed that enables an accurate prediction of PVDF structure properties, particularly morphological and a fraction of the β-phase content. It was found that the fraction of β-phase is considerably affected by evaporation rate so that the high concentration of PVDF and DMF/acetone decreases the evaporation rate of the solution resulting in a formation of a high fraction β-phase content. The electrospinning method was found to be very effective to promote the β-phase formation in PVDF nanofiber. Additionally, electrospun PVDF nanofibers were experienced high electrical field and mechanical stretching during the fabrication which eliminates a need for the post-treatment process. This study proposes a core-shell structured PVDF-graphene oxide (GO) nanofiber composite, in which the polar phase content and piezoelectric properties are considerably improved. The results indicate that only 0.2 wt. % of GO is enough to nucleate most of the PVDF polymer chain. It was found that the β-phase content in core-shell structured PVDF-GO nanofiber composite can reach up to 92 % for which is 23% and 73% higher that of electrospun PVDF and spin coated PVDF, respectively. This suggests that the core-shell structure of PVDF-GO is effective in improving the phase transformation of α-phase to β-phase, even at a low content of GO. As an interior core-shell, the GO is solidified into nanofiber form which increases the number of heterogeneous nucleation sites to interact with the PVDF polymer chain. The d33 piezoelectric coefficient of PVDF-GO was found to be 61 pm/V which is almost two times higher than PVDF nanofiber. The enhancement of the piezoelectric coefficient can be attributed to the higher β-phase content which can induce a stronger displacement in the sample as a result of the applied electrical field. This might be because of the interaction between the π-bond in GO with the fluorine atoms and hydrogen atoms on adjacent carbon atoms in PVDF polymer chains. It was found that the efficiency of the PVDF sensor in detecting the signal is not sensitive to the amplitude of the transmitted signal. Also, the transmitted signal\u27s amplitude has an insignificant effect on the attenuation rate of the transmitted signal over the distance. It means that the efficiency of the PVDF sensor in detecting the Lamb wave signal is not affected by the amplitude of the transmitted signal. However, the efficiency of the PVDF sensor to detect the transmitted signal is highly affected by the distance between the transducer and receiver. The results indicate that the PVDF device is less efficient in detecting the transmitted signal either at a low-frequency range (\u3c1 kHz) or the higher range of frequency (\u3e 100 kHz). The optimized frequency was found to be in the range of 1 kHz to 100 kHz to enhance the efficiency of the PVDF sensor. The efficiency of PVDF sensor for detecting the acoustic wave was also studied by hammer impact testing. These results clearly indicate that the sensor is able to detect different magnitudes of surface acoustic waves propagating on the surface. The higher of the impact energy applied to the concrete, the higher the voltage generated by electrospun PVDF AE sensor. The results of this thesis can assist in adopting the electrospun PVDF piezoelectric sensor in a variety of sensing and energy harvesting applications in civil engineering infrastructure. (Abstract shortened by ProQuest.

Feasibility of using Natural SCMs in Concrete for Infrastructure Applications

Nowadays concerns about the future availability of fly ash have arisen due to the implantation of pollution control devices in coal combustion plants and increased blending of powder river basin coals, both of which can influence the composition (and hence quality) of the resulting fly ash. An experimental study was conducted to evaluate the feasibility of incorporating natural supplementary cementitious materials (SCMs) mainly perlite, pumice, and zeolite in civil infrastructure applications. The influence of selected natural SCMs, on the hydration behavior, key fresh and hardened properties of cement paste and concrete mixtures was compared to mixtures without any SCM and with fly ash. The results indicated that Perlite may be the suitable material regarding fresh properties, but low pozzolanic reactivity and a reduction in compressive strength and modulus of elasticity may reduce its implementation for structural applications. Mixtures with 15 wt% pumice was shown to have similar properties to the reference mixture without fly ash, but had increased SP demand and low workability retention, making them more suitable for precast applications compared to ready-mix concrete. The zeolite performed very well in the hardened state, but had high admixture demand and inferior workability retention. From this study, it can be concluded that each of the three investigated alternatives SCMs that may be used to replace class C fly ash in concrete infrastructure applications

Influence of addition sequence of materials on rheological properties of self-compacting concrete

In order to determine how the mixing process influences the fresh properties of self-compacting concrete (SCC), a SCC mix composition was produced using six different mixing procedures, varying the addition sequence of the materials and the initial moisture content of the sand. When pre-mixing the aggregates with water, or soaking them for 12 hours, part of the water is absorbed by aggregates, resulting in a lower slump flow and higher dynamic yield stress, compared to the case when aggregates were added to the cement paste. The measured values for the V-funnel flow time and plastic viscosity were slightly higher

Admixture Compatibility with Natural Supplementary Cementitious Materials

It is anticipated that the use of fly ash in concrete will be significantly limited in the future due to recent restrictions on coal burning power plants to reduce air pollution. This paper aims to study the compatibility between some natural supplementary cementitious materials (SCMs): including perlite (PL), pumice (PM), and zeolite (ZL) with one type of superplasticizer and two types of air-entraining admixtures (AEA), mainly by analyzing the rheological properties and air-void system, respectively. It was found that both the porosity and amount of organic content of SCMs can play a significant role in air stability in cementitious materials. The organic AEA was found to be more effective than the synthetic AEA to produce a stable air system in cementitious materials due to the low required admixture dosage, while the synthetic air entraining admixture showed superior performance in the retention of the air system and resulted in better compatibility compared to the organic air-entraining admixture. In general, the addition of SCMs in non-air-entrained concrete mixtures resulted in similar rheological properties as well as similar compressive strength compared to the air-entrained concrete. This confirms that the air void system has successfully been introduced in the concrete mixture without any incompatibilities

Determination of critical time points in non-collision incidents of elderly passengers in standing position on urban bus

Objective: Due to the reduced physical ability of elderly, the occurrence of non-collision incidents is higher for these passengers in standing position. Therefore, the purpose of the present study is to determine the critical time points of non-collision incidents using the level of leg muscle activity in elderly standing passengers on urban bus. Methods: To determine the critical time points in the occurrence of non-collision incidents, the level of muscular activity of the standing passengers was analyzed using a surface electromyography (surface EMG) device during the movement scenario of the bus. The results of assessing the leg muscle activity was analyzed in SPSS software. Results: The contraction pattern of the leg muscles in standing passengers was consistent with Newton’s First Law. The results showed that the level of muscular activity decreased in the right leg muscles when changing the phase of bus motion from acceleration to constant velocity. This level of muscular activity in the left leg muscles increased when constant velocity changed to deceleration. These changes were quite significant in the medial gastrocnemius and soleus muscles (P \u3c 0.05). Conclusions: According to these findings, it was found that the acceleration and deceleration phases, especially the starting and changing phases of bus motion, are the most critical time points in the occurrence of non-collision incidents in elderly standing passengers on urban bus