Preliminary experimental study on solid-fuel rocket scramjet combustor

Liquid or gaseous fuel scramjet technology has made great progress, and there has been some research attention to solid-fuel scramjet. A new scramjet configuration using solid fuel as propellant, namely solid-fuel rocket scramjet, is tested experimentally. It consists of two combustors. One is a rocket combustor used as gas generator, and the other is a supersonic combustor used for secondary combustion. The experiment simulates a flight Mach number of 4 at high altitude (stagnation temperature and pressure are 1170 K and 1.16 MPa, respectively), and metalized solid fuel is used as propellant. The results reveal that fuel-rich gas from the gas generator can burn with air in the supersonic combustor. Preliminary evaluation results show that the combustion efficiency of the propellant is about 90%, and the total pressure recovery coefficient in the supersonic combustor is about 0.6. These results indicate that the configuration of solid-fuel rocket scramjet is feasible.     

Mode transition process in a typical strut-based scramjet combustor based on a parametric study

The combustion performance of hydrogen fuel in a scramjet combustor has been a popular focus for scholars all over the world. In this study, the influence of the jet-to-crossflow pressure ratio on combustion performance in a scramjet combustor was investigated numerically, and the influence of a wall-mounted cavity was evaluated. The simulations were conducted using the Reynolds-averaged Navier-Stokes (RANS) equations coupled with the renormalization group (RNG) k-ε turbulence model and the single-step chemical reaction mechanism. This numerical approach was validated by comparing predicted results with published experimental shadowgraphs and velocity and temperature measurements. When the pressure of the wall-injector increases, the performance of the combustor decreases. At the same inflow condition, this may lead to a scram-to-ram mode transition. The cavity adopted in this study would prevent pre-combustion shock waves from pushing out of the isolator and help to stabilize the flow field, but it would decrease the mixing and combustion efficiencies.     

Using concept mapping to improve poor readers’ understanding of expository text

The present study examined whether the use of concept mapping is more effective in teaching expository material in comparison to a traditional, lecture only, approach. Its objective was threefold. First, to determine if multimedia concept mapping produces differential learning outcomes compared to digital text-based concept mapping. Secondly, to compare the above experimental approaches to traditional teaching and finally to demonstrate if there are significant differences in the level of satisfaction reported by children under the three instructional approaches used. Thirty fifth grade children participated from which three groups of poor readers were formed, matched on age, gender and reading ability. The two experimental groups were taught with the use of digital text-based and multimedia concept maps respectively and the control group was subjected to the traditional teaching method of expository material. Each group had three sessions of instruction on three different expository texts. The results indicated that concept mapping can be an effective means for teaching expository content. However, there were no differential learning outcomes when adding multimedia elements to concept maps. Moderate satisfaction was reported for all three approaches. The findings coincide with the body of literature emphasizing the importance of concept mapping in the learning and instruction of children with reading difficulties. The study’s results inform potential educators on the use of multimedia with poor readers in elementary school.     

Differentiating the Sources of Taiwanese High School Students’ Multidimensional Science Learning Self-Efficacy: An Examination of Gender Differences

The main purpose of this study was to investigate Taiwanese high school students’ multi-dimensional self-efficacy and its sources in the domain of science. Two instruments, Sources of Science Learning Self-Efficacy (SSLSE) and Science Learning Self-Efficacy (SLSE), were used. By means of correlation and regression analyses, the relationships between students’ science learning self-efficacy and the sources of their science learning self-efficacy were examined. The findings revealed that the four sources of the students’ self-efficacy were found to play significant roles in their science learning self-efficacy. By and large, Mastery Experience and Vicarious Experience were found to be the two salient influencing sources. Several gender differences were also revealed. For example, the female students regarded Social Persuasion as the most influential source in the “Science Communication” dimension, while the male students considered Vicarious Experience as the main efficacy source. Physiological and Affective States, in particular, was a crucial antecedent of the female students’ various SLSE dimensions, including “Conceptual Understanding,” “Higher-Order Cognitive Skills,” and “Science Communication.” In addition, the variations between male and female students’ responses to both instruments were also unraveled. The results suggest that, first, the male students perceived themselves as having more mastery experience, vicarious experience and social persuasion than their female counterparts. Meanwhile, the female students experienced more negative emotional arousal than the male students. Additionally, the male students were more self-efficacious than the females in the five SLSE dimensions of “Conceptual Understanding,” “Higher-Order Cognitive Skills,” “Practical Work,” “Everyday Application,” and “Science Communication.”     

Web technologies applied to virtual heritage: An example of an Iberian Art Museum

Nowadays, some virtual museums include 3D room scenes to show the models of its pieces, just like in real museums. Nevertheless, the generation and maintenance of this kind of scenes is generally difficult and should be done by an expert. For example, any change such as including a new piece or modifying the position of an existing fragment usually requires a different design and the creation of a new scene. In this paper we present a case study on the development of a web-based application to automatize this process. To this end, a database to store both graphic and non-graphic information about the pieces, and some 3D rooms to show them has been created. The designed scenes only contain some pieces of furniture to exhibit the fragments, which will be subsequently included. Thus, when a room is loaded in the web page, its associated pieces are obtained through a query in the database and its models are dynamically included in the original scene. Therefore, the position changes or the inclusion of new pieces are not performed in the 3D model, but in the database. Our application makes the transmission of the knowledge to the general public easier because any new discovered piece can be included in a existing museum effortlessly.     

A note on the Marcinkiewicz integral operators on Fp^a,q

In this paper, we shall prove that the Marcinkiewicz integral operator #n, when its kernel Ω satisfies the L^1-Dini condition, is bounded on the Triehel-Lizorkin spaces. It is well known that the Triehel-Lizorkin spaces are generalizations of many familiar spaces such as the Lehesgue spaces and the Soholev spaces. Therefore, our result extends many known theorems on the Marcinkiewicz integral operator. Our method is to regard the Marcinkiewicz integral operator as a vector valued singular integral. We also use another characterization of the Triehel-Lizorkin space which makes our approach more clear.     

Towards achieving the Sustainable Development Goals: Revisiting language of instruction in Tanzanian secondary schools

Research has been conducted on the detrimental effects of using a foreign language for learning in Tanzania’s secondary schools. While most studies recommend the use of a familiar language for instruction, the use of a foreign language in secondary education in Tanzania has been maintained. This has many consequences on the quality of education, and contributes to student dropout. Presenting a study carried out in the semi-rural areas of Dar es Salaam region in Tanzania, this article examines the extent to which language of instruction (LOI) contributes to school dropout. It postulates that the use of a foreign language for teaching and learning in Tanzanian secondary schools hinders the achievement of the United Nations’ Sustainable Development Goals (SDGs). The study’s findings, drawn from exploratory and qualitative narrative research, indicate that, notwithstanding the presence of several other factors, the use of a foreign language as LOI is a major contributor to student dropout. The use of an unfamiliar language of instruction contributes to students’ lack of interest in and disengagement from learning, which ultimately pushes them out of the school system. This is because students usually perform poorly when an unfamiliar language is used as the language of examination and in classroom interaction. The study also reveals that the voices of both teachers and students are not in consonance with what would be expected in an ideal classroom teaching and learning environment. Student dropout from secondary education caused by an inappropriate LOI leads to myriad further problems which, in turn, negatively affect realisation of the SDGs in Tanzania. This article, therefore, concludes that LOI needs to be strongly factored into the development agenda. In order to ensure equitable access to quality secondary education, as required by SDG 4, the Government of Tanzania needs to adopt a language policy that promotes effective teaching and equal access to quality education in secondary schools.