Search results

This study aims to solve the problems of low flow rate and low efficiency of micropumps in high-frequency applications. This micropump system was proposed to meet the requirements of 1–5 ml/min for microthrusters or drug delivery devices.

In this paper, a comprehensive analysis indicator and numerical procedure were disclosed and used to demonstrate the fluid dynamic characteristics and performance of a micropump. Accordingly, the reliability of the two-way coupling calculation was ensured through mutual verification of the real structure and the numerical system.

The research results indicate that the Polydimethylsiloxane (PDMS) microchannel can realize the contraction and expansion mechanism, allowing the fluid to generate different levels of pressure gradient during the working stroke and also enhancing the characteristics of energy consumption and storage of the flow field.

The pressure gradient between the fluid and PDMS microchannel can facilitate the improvement of the fluid backflow in a micropump. Therefore, in terms of performance improvement, the PDMS micropump increased the maximum backflow and optimum efficiency by approximately 50 and 90%, respectively.

Recently, the acoustic characteristics of indoor spaces have been perceived to be more important due to the economic development needs of societies. At the same time, container houses have gradually become more widely used in many applications because of their sustainability and ease of use. In spite of their convenience, these container units still need to foster pleasant and quiet sound environments. The paper aims to discuss these issues.

In this paper, commercial software, designed by Ecotect Analysis, has been used to evaluate the sound characteristics of container houses. As a result, the decorated materials in such a small indoor space have been redesigned for the acoustic comfort of users based on the optimal reverberation time (RT). First, a three-dimensional model of the container house was constructed using the software’s default tools. Then, the indoor acoustic characteristics of various design conditions were obtained from the simulation process undertaken.

By comparing the experimental and simulation results, excellent agreement was observed which verified the feasibility of the software. The original container house experienced an RT distribution of 140-315 ms. After selecting a suitable interior design material, its RT distribution was measured at 160-680 ms.

Following the design process described, spatial designers can assess the indoor acoustic characteristics at the concept design stage and ensure that a decent acoustic comfort environment is derived in their building designs. Meanwhile, such modifications should improve the quality of living for residents of container houses and construction cost reductions might be implemented.

This study examines how project uncertainties (environmental uncertainty and participant uncertainty) affect guanxi and contractual governance and assesses the mediating role of guanxi governance between project uncertainty and contractual governance.

Data were collected in two stages from Chinese contractors. First, in-depth interviews were conducted with nine construction engineering project practitioners in different contracts as a pilot for questionnaire designing. Second, a cross-sectional questionnaire survey was conducted with professionals and practitioners of construction enterprises to collect primary data. Partial least squares structural equation modeling (PLS-SEM) was used to test seven hypotheses based on data collected from 198 respondents.

Project environmental uncertainty promotes the use of guanxi governance, while project participant uncertainty hinders it; the relationship between both types of uncertainty and contractual governance is the same as with guanxi governance. Furthermore, guanxi governance promotes contractual governance and partially mediates project environmental uncertainty and contractual governance and a complete mediating role between project participant uncertainty and contractual governance.

As the interviewed samples are mainly from China, the study should be replicated using large representative samples from East Asian countries, such as Japan and South Korea, to gain a more comprehensive understanding of the influence of guanxi governance. Further, while the internal consistency reliability and convergent validity of the questionnaire data in this study align with the standards, a larger sample size would improve the reliability and validity of the research results and better represent the overall work situation of contractors, owners and public policymakers.

The results provide insights into project governance research and have implications for construction practitioners in deploying governance-related resources.

Privacy and security concerns of consumers have been touted as one of the hindrances to the growth of e-commerce. These concerns increase the risk perception of consumers. Understanding the consequences of privacy and security concerns and their relationship to risk perceptions may provide a solution. The relationship between privacy and security is investigated using the theory of planned behavior. The study aims to examine the relationship of trust, privacy and security concerns to the risk perception adoption of e-commerce. The results from a survey validate the model.

Data were collected using survey from undergraduate business students. The respondents were requested to select a specific product that they plan to purchase in the next six months. After selecting a product, the respondents were requested to report an online company that they have recently visited which offers the selected product. The respondents were requested to fill out the survey with regard to their selected online company. Time given was approximately 20 min.

The results suggest that privacy and security concerns and trust beliefs had effects on risk perception. Among these effects, trust had the largest effect followed by privacy and security concerns. Furthermore, risk perception and trust beliefs had effects on attitude. The effect of trust beliefs on attitude was larger than the effect of risk perception on attitude. Similarly, subjective norm, perceived behavioral control and attitude had a positive and direct effect on intention to be involved in e-commerce.

The first limitation of this study is the use of student subjects. Because this study took place in an educational setting, its generalizability to the general population of consumers lacks to some degree. The second limitation of this study is mono-method bias.

The effect of privacy concerns on risk perception was larger than that of security concerns. Because the consumers get more experienced and sophisticated using the Web, the security concerns that they may have had at the beginning are not reflected in their risk perceptions. It is likely that they have adopted protective measures on their own to defend their privacy online. An example of such a measure would be providing false information to online companies when asked to submit personal information.

The major contributions of this study are developing and validating an integrative framework of e-commerce adoption at the individual level. The model includes privacy and security concerns, risk perception and trust beliefs. This study also highlighted the distinction of constructs of privacy and security concerns and showed their differential effects on other related constructs in the research model.