Guangbin Tan, Ping Yang, Tianbo Li, Tao Xi, Xiaoming Yuan and Jianming Yang
The purpose of this paper is to provide a systematic method to perform analysis and test for vibration‐thermal strain behavior of plastic ball grid array (PBGA) assembly by…
Abstract
Purpose
The purpose of this paper is to provide a systematic method to perform analysis and test for vibration‐thermal strain behavior of plastic ball grid array (PBGA) assembly by considering thermal and vibration loading mode. Also to investigate the dynamic behavior of PBGA assembly by considering loading modes for design and reliability evaluation of PBGA packaging.
Design/methodology/approach
A PBGA assembly prototype with different structure and material parameters is designed and manufactured. Based on investigation of the structural and physical parameters of PBGA sample, the vibration‐thermal strain test is developed to measure the strain distribution at the surface of the BT (bismaleimide triazine) substrates and PCB (printed circuit board) surface under vibration‐thermal cycling loading such as random vibration and the temperature is changed from 0°C to 100°C.
Findings
The test results show that the loading modes have different impact on PCB, EMC and substrate, respectively. In the meantime, it is shown that the characteristics of the compound mode is not the linear accumulative result by single vibration mode and single thermal loading mode as forecasted. The nonlinear mechanism for these modes application is the future work for progress.
Research limitations/implications
It is very difficult to set up a numerical approach to illustrate the validity of the testing approach because the complex loading modes and the complex structure of PBGA assembly. The research on an accurate mathematical model of the PBGA assembly prototype is a future work.
Practical implications
It implies a potential design characteristic for future application of PBGA assembly. It also builds a basis for future work for design and reliability evaluation of BGA package.
Originality/value
This paper fulfils useful information about the thermal‐vibration coupling dynamic behavior of PBGA assembly with different structure characteristics, materials parameters.
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Ping Yang, Xiusheng Tang, Yu Liu, Shuting Wang and Jianming Yang
The purpose of this paper is to perform experimental tests on fatigue characteristics of chip scale package (CSP) assembly under vibration. Some suggestions for design to prolong…
Abstract
Purpose
The purpose of this paper is to perform experimental tests on fatigue characteristics of chip scale package (CSP) assembly under vibration. Some suggestions for design to prolong fatigue life of CSP assembly are provided.
Design/methodology/approach
The CSP assembly which contains different package structure modes and chip positions was manufactured. The fatigue characteristics of CSP assembly under vibration were tested. The fatigue load spectrum of CSP assembly was developed under different excitation. The fatigue life of chips can be estimated by using the high-cycle fatigue life formula based on different stress conditions. The signal–noise curve shows the relationship between fatigue life and key factors. The design strategy for improving the fatigue life of CSP assembly was discussed.
Findings
The CSP chip has longer fatigue life than the ball grid array chip under high cyclic strain. The closer to fixed point the CSP chip, the longer fatigue life chips will have. The chip at the edge of the printed circuit board (PCB) has longer fatigue life than the one in the middle of the PCB. The greater the excitation imposed on the assembly, the shorter the fatigue life of chip.
Research limitations/implications
It is very difficult to set up a numerical approach to illustrate the validity of the testing approach because of the complex loading modes and the complex structure of CSP assembly. The research on an accurate mathematical model of the CSP assembly prototype is a future work.
Practical implications
It builds a basis for high reliability design of high-density CSP assembly for engineering application. In addition, vibration fatigue life prediction method of chip-corner solder balls is deduced based on three-band technology and cumulative damage theory under random vibration so as to verify the accuracy of experimental data.
Originality/value
This paper fulfils useful information about the dynamic reliability of CSP assembly with different structural characteristics and material parameters.
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Dong Yang, Zhenxiang Liu, Ting Shu, Lijia Yang, Jianming Ouyang and Shen Zhi
Helical coil electromagnetic launchers (HEMLs) using motion-induced commutation strategy solve the problem of synchronization control perfectly. HEMLs can meet the requirements of…
Abstract
Purpose
Helical coil electromagnetic launchers (HEMLs) using motion-induced commutation strategy solve the problem of synchronization control perfectly. HEMLs can meet the requirements of multiple applications such as the electromagnetic catapult, electromagnetic mortar and high-velocity coilgun. The trade-off between the velocity and efficiency is an important basis for these different applications. To optimize such objectives before actual design, the purpose of this paper is to focus on the efficient and flexible calculation model and algorithm. A novel structure of HEML is proposed after the transient simulation by this algorithm, which can improve the energy conversion efficiency and suppress the muzzle arc without affecting the velocity too much.
Design/methodology/approach
The equivalent circuit model of the launcher is established and the governing equations are derived. A combination of the four-stage Runge–Kutta method and the trapezoidal quadrature formula are used to solve the governing equations.
Findings
With smaller number of turns in the coils of HEML, the velocity is larger and the efficiency is lower. The non-uniform HEML is an effective option to improve the energy conversion efficiency and to suppress the muzzle arc with almost the same muzzle velocity as the conventional HEML.
Originality/value
The paper presents a common model and a flexible fast numerical method which can be used in multi-objective optimization of HEMLs such as the genetic algorithm. A new structure of the non-uniform HEML is proposed to improve the energy conversion efficiency and to suppress the muzzle arc of the launcher.
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Ying Pan, Lia H. Sun, Heqing Yang and Jianming Zheng
“Library + cultural tourism” (LCT) is a new direction for the sustainable development of libraries, but few scholars have researched it from a tourist perspective. The purpose of…
Abstract
Purpose
“Library + cultural tourism” (LCT) is a new direction for the sustainable development of libraries, but few scholars have researched it from a tourist perspective. The purpose of this paper is to identify what factors affect tourist satisfaction (TS) with LCT, reveal the interaction among these factors and provide strategies for better library services.
Design/methodology/approach
This study collected 5,308 comments on Tianjin Binhai Library from three popular online travel communities. Grounded theory was adopted to identify what factors affect TS with LCT and reveal the interaction among these factors.
Findings
The results indicated that TS with LCT was affected by complex factors related to tour plans, tour expectations, cultural characteristics, environment, support services and emotions. Cultural characteristics, environment and support services were impacted by tour plans and tour expectations, which directly or indirectly affected TS mediated by emotions. TS further influenced their expectation of their next tour.
Originality/value
This paper uncovered critical problems with LCT using a case study of Tianjin Binhai Library. The results provide a reference for library practitioners to develop better library services for tourists and regular users/readers.
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Zhe Cheng, Yongjian Ke, Zhenshan Yang, Jianming Cai and Huanming Wang
As an innovation model for infrastructure and public service delivery, public–private partnership (PPP) has been widely adopted around the world. The knowledge spillover effect…
Abstract
Purpose
As an innovation model for infrastructure and public service delivery, public–private partnership (PPP) has been widely adopted around the world. The knowledge spillover effect and policy diffusion mechanism have played an important role in promoting the development of PPP in the context of globalization. A comparative evaluation of the policy and management of PPP in different countries will help to understand the development of PPP, provide decision-making reference for PPP policy embedded with specific national conditions of each country, and also contribute to the global PPP knowledge body.
Design/methodology/approach
Based on the principle of comparability and representativeness, this study selected three countries, namely, China, India, and the United Kingdom for comparative analysis. This study first introduced the policy process and key institutions of PPP in three countries. Secondly, a comparative analysis of the development characteristics and application of PPP was conducted based on the official database of three countries. Finally, the differences, influencing factors and development trends of international PPP development were analyzed based on the comparative research results, and suggestions for PPP policy and management were put forward.
Findings
The research results indicate the development fluctuation and unbalanced spatial distribution of PPPs are a common phenomenon in the three countries. The UK has a significant impact on the policy and development of PPP in other countries. However, under the combined influence of factors such as economic, urbanization, political regime and social culture, there are significant differences in the PPP institution, application, and project characteristics in various countries. Due to international exchanges and knowledge spillovers, as well as the promotion of intermediaries, the development of PPP worldwide tends to converge.
Practical implications
Through conducting an international comparison of PPPs based on project data, this study provides a detailed and visualized overview of PPPs and a better understanding of PPP policy and management in different countries. The findings will be of interest to PPP investors, officers, practitioners, policymakers, researchers, and analysts. It enriches the portrait of global PPP market research, helps governments to improve the design of PPP institutions and policies, and provides references for decision-making of international investors when stepping into a new market.
Originality/value
This study is the first attempt to systematically compare and analyze the global PPP difference and development trend based on PPP project databases of different countries. Different from previous PPP comparative research based on perception data, the project data-based comparative analysis in this study is helpful to understand the characteristics, interrelations, and trends of global PPP development and enrich the existing PPP knowledge body. This study also proposes that it is possible to establish a global PPP knowledge community in the context of globalization and global production network.
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Jianming Wang, Guotao Ye and Jingshu Yang
Influencer marketing has emerged as a key strategy for brands to promote green products. The effectiveness of virtual influencers – a newer type of endorser – for these products…
Abstract
Purpose
Influencer marketing has emerged as a key strategy for brands to promote green products. The effectiveness of virtual influencers – a newer type of endorser – for these products remains unclear. This study aims to compare the effectiveness of virtual and human influencers in promoting green products and to uncover the key mechanisms that drive their influence.
Design/methodology/approach
In this research, the hypotheses were examined across three experimental studies. Study 1 initially investigated the effectiveness of virtual influencers in endorsing green products. Study 2 identified perceived altruistic motivation and perceived congruence of product and influencer as key mechanisms. Study 3 explored the moderating effect of language type (rational vs emotional).
Findings
The findings indicate that virtual influencers are generally less effective than human influencers in promoting green products, largely due to lower perceived altruistic motivation and congruence. Yet, using rational language in promotional posts can enhance the effectiveness of virtual influencers in endorsing these products.
Originality/value
This study combines the mind perception theory with the match-up hypothesis to explore the intrinsic mechanisms of perceived altruistic motivation and congruence, specifically from an emotional perspective, based on the unique attributes of virtual influencers and green products. These insights guide brands in selecting suitable endorsers for green products in the context of increasing environmental awareness and digitalization.
Details
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Zhang Feifei, Cai Jianming and Liu Gang
In Beijing, urban agriculture (UA) experienced a corkscrew development with its role changing in decades: It has evolved from the purely production mode to multi-functional urban…
Abstract
In Beijing, urban agriculture (UA) experienced a corkscrew development with its role changing in decades: It has evolved from the purely production mode to multi-functional urban agriculture, fulfilling both social and ecological demands. At present, the practice of UA as well as the number of rural to urban migrants is growing rapidly in peri-urban Beijing. Through Multi-stakeholder Process for Action planning and Policy Design (MPAP) methodology and four in-depth case studies, we can see that UA activities are playing very important roles in reshaping peri-urban Beijing. Socially, UA induces the emergence of new migrant communities. While migrants rebuild their social network, they are changed by the city as well, which has also changed the local community. The new comers are on their way to creating a new balance. Physically, urban and peri-urban farmland limits urban sprawl, supplies agricultural products for everyday life, and reserves urban green spaces for recreation and leisure for citizens in Beijing, which has changed the landscape and land use and land cover (LUCC) pattern greatly. Under Beijing's land policy, the concentric configuration spatial allocation through multi-functional UA is formed, which at the same time due to migrants' UA activities are creating harmful and low efficient land use pattern which should be of concern.
Details
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Van Thac Dang, Ninh Nguyen and Jianming Wang
A review of 67 articles in the indoor environmental quality (IEQ) literature published from 2010 to 2020 reveals that none of prior studies have determined the IEQ of physical…
Abstract
Purpose
A review of 67 articles in the indoor environmental quality (IEQ) literature published from 2010 to 2020 reveals that none of prior studies have determined the IEQ of physical retailers and its impact on consumers. To fill such a gap, this study investigates the influence of physical retailers' IEQ on consumer purchase intention. The mediating roles of hedonic experience and perceived brand value (PBV) in this relationship are also determined. Furthermore, the moderating effect of perceived service quality (PSQ) on the link between physical retailers' IEQ and PBV is clarified in this study.
Design/methodology/approach
This study uses structural equation modeling (SEM) to analyze a sample data of 996 consumers in China.
Findings
Results show that physical retailers' IEQ has a positive impact on consumer purchase intention. Hedonic experience mediates the link between IEQ and purchase intention. PBV also mediates the relationship between IEQ and purchase intention and that between hedonic experience and purchase intention. In addition, PSQ moderates the relationship between IEQ and PBV.
Originality/value
To the best of the authors’ knowledge, this study is the first to determine the impact of IEQ on consumers in the physical retailer context. Specifically, this study enriches our knowledge about the relationship between physical retailers' IEQ and consumer purchase intention with the mediating and moderating mechanisms of hedonic experience, PBV and PSQ. The findings fill the research gaps in the IEQ literature that has ignored the impact of IEQ on consumers' perception and behavioral intention in the physical retailer context. Furthermore, this research provides evidence for retailer managers to understand and improve physical stores' IEQ.
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Muhammad Rafi, Khurshid Ahmad, Salman Bin Naeem, Asad Ullah Khan and Zheng JianMing
Digital libraries promote and accelerate scientific research in academic institutions. The subscribed database resources of digital libraries have become an increasingly valuable…
Abstract
Purpose
Digital libraries promote and accelerate scientific research in academic institutions. The subscribed database resources of digital libraries have become an increasingly valuable asset for researchers. Database resources help generate new ideas, determine research directions and promote productive academic interaction between teachers and students in the information age. The purpose of this study is to examine the use of electronic resources by students in various databases, the research productivity of the faculty in the science network and the number of students who graduate each year.
Design/methodology/approach
This study uses a quantitative method to collect secondary data from the central database of the Higher Education Commission (HEC) for the population of 26 universities for 2 years (2015–2016). In addition to the HEC digital library, data was also collected from the Web of Science to determine the quality academic performance of faculty and researchers. Moreover, in the study, the total strength of teaching staff and doctoral faculty was extracted from the HEC website for investigation. The authors applied the Spearman’s correlation test to the secondary data using Statistical Package for Social Sciences version 25.
Findings
The correlation results of the enrolled students and the downloaded papers from various databases were statistically insignificant (p > 0.05). However, the result showed a positive correlation (p < 0.05) between the use of selected/known databases from a number of databases accessed by the HEC. More importantly, it turns out that the faculty’s productivity in the scientific network and the number of students who graduated from public and private universities are found to be insignificant (p > 0.05). However, the authors found a positive correlation (p < 0.05) between doctoral and non-doctoral faculties, which show that a significant number of non-doctoral faculties are still actively involved in teaching and research.
Originality/value
Research based on academic activities by faculties and students, performed for the first time on the basis of secondary data, will help the HEC and university management to determine the right direction and develop plans to improve academic performance and research quality.
Details
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Qi Wang, Pengcheng Zhang, Jianming Wang, Qingliang Chen, Zhijie Lian, Xiuyan Li, Yukuan Sun, Xiaojie Duan, Ziqiang Cui, Benyuan Sun and Huaxiang Wang
Electrical impedance tomography (EIT) is a technique for reconstructing the conductivity distribution by injecting currents at the boundary of a subject and measuring the…
Abstract
Purpose
Electrical impedance tomography (EIT) is a technique for reconstructing the conductivity distribution by injecting currents at the boundary of a subject and measuring the resulting changes in voltage. Image reconstruction for EIT is a nonlinear problem. A generalized inverse operator is usually ill-posed and ill-conditioned. Therefore, the solutions for EIT are not unique and highly sensitive to the measurement noise.
Design/methodology/approach
This paper develops a novel image reconstruction algorithm for EIT based on patch-based sparse representation. The sparsifying dictionary optimization and image reconstruction are performed alternately. Two patch-based sparsity, namely, square-patch sparsity and column-patch sparsity, are discussed and compared with the global sparsity.
Findings
Both simulation and experimental results indicate that the patch based sparsity method can improve the quality of image reconstruction and tolerate a relatively high level of noise in the measured voltages.
Originality/value
EIT image is reconstructed based on patch-based sparse representation. Square-patch sparsity and column-patch sparsity are proposed and compared. Sparse dictionary optimization and image reconstruction are performed alternately. The new method tolerates a relatively high level of noise in measured voltages.