Commutation Technique for High Frequency Link Inverter without Operational Limitations and Dead Time

An improved commutation technique for the ac-ac output converter circuit of a pulse width modulated high frequency link (HF-link) inverter has been investigated. The high frequency link inverter converts a DC input voltage into line frequency AC output voltage using a high-frequency transformer for voltage step-up and galvanic isolation, without an intermediate rectification and DC bus. In this topology, there is a direct ac-ac converter, which processes the HF-link square-wave voltage into the desired sinusoidal ac output voltage. To do this requires a commutation method to prevent shoot-through when output current changes direction or commutates from one switch to the next. Conventionally, dead time is used but this adds distortion to the output waveform. Previously a commutation technique without dead time was introduced, but it required a number of assumptions on the inverter load impedance and link voltage characteristics that made it useful for a stand-alone R-L load but not practical for grid connection. The commutation method in this paper does not require dead time and does not impose any limitation on the output inductance and link voltage magnitude and frequency. Simulations, results experimental results and detailed analysis of output current THD values are presented

Commutation Technique for High Frequency Link Inverter without Operational Limitations and Dead Time

An improved commutation technique for the ac-ac output converter circuit of a pulse width modulated high frequency link (HF-link) inverter has been investigated. The high frequency link inverter converts a DC input voltage into line frequency AC output voltage using a high-frequency transformer for voltage step-up and galvanic isolation, without an intermediate rectification and DC bus. In this topology, there is a direct ac-ac converter, which processes the HF-link square-wave voltage into the desired sinusoidal ac output voltage. To do this requires a commutation method to prevent shoot-through when output current changes direction or commutates from one switch to the next. Conventionally, dead time is used but this adds distortion to the output waveform. Previously a commutation technique without dead time was introduced, but it required a number of assumptions on the inverter load impedance and link voltage characteristics that made it useful for a stand-alone R-L load but not practical for grid connection. The commutation method in this paper does not require dead time and does not impose any limitation on the output inductance and link voltage magnitude and frequency. Simulations, results experimental results and detailed analysis of output current THD values are presented

Omnichannel Innovation Lab: Incorporating Design Thinking into a Merchandising Course

This paper illustrates how the Human-Centered Design (HCD) approach (aka. design thinking) was incorporated in the existing merchandising course to foster creativity among students. The five key learning objectives of the Omnichannel Innovation Lab course included; (1) gain a deep understanding of omnichannel retailing, (2) develop ethnographic research skills to gain an empathetic understanding of consumer needs, (3) apply the design thinking process, (4) develop omnichannel innovations and (5) improve collaboration skills

Content Analysis of M-Commerce: A Comparison of Apparel and Non-apparel Sites

To conduct a systematic and comprehensive assessment on mobile sites\u27 performance in facilitating mobile shopping, this study examined whether availability of service attributes differ between apparel and non-apparel mobile sites. The comprehensive coding guide developed and validated in the context of e-commerce research guided the conceptual development of this study. Mobile sites (N=194) from Internet Retailer (2011) were selected for content analysis. The updated m-commerce coding guide included the five dimensions such as convenience, customization, information, communication and visual merchandising. The findings show that apparel mobile sites outperform non-apparel sites for the convenience, customization and communication dimensions. No difference was found for the information and visual merchandising dimensions. The findings of this exploratory study offer a useful snap shot of the current performance of m-commerce sites for both scholars and practitioners

The Relationships of SNS Use, Social Achievement Goals, and Life Satisfaction: A Study of Korean College Students

Social networking sites (SNS) provide efficient communication. However, SNS use sometimes risks a user’s life satisfaction. Based on the prior findings that one’s social orientation influences the impact of SNS use on life satisfaction, this study examined the pathways to explain how SNS use affects individuals’ life satisfaction through social achievement goals. A main path model and two gender-specified path models were tested using 438 Korean college student samples. The results showed that social development goals mediated the relationships between active SNS use and life satisfaction across all three path models. The social demonstration approach goal was positively predicted by active SNS use in the main model and the male model, but it did not predict life satisfaction in both models. The social demonstration-avoidance goal was positively predicted by active SNS use in the main and female models. Still, it negatively predicted life satisfaction in both models. Implications and directions for future study are discussed

Factors Affecting Initial Trust in an Online Shopping

With the rapid growth of online retailing, consumers have a vast number of websites to choose from when shopping online. While multichannel retailers that expanded online based off their successful brick-and-mortar or catalog operations benefited from their existing customer bases and brand/retailer names, many pure e-retailers have been challenged by their lack of brand equity in the market. Due to lower barriers to market entry, a number of new online businesses are flourishing, yet only a small fraction of them can survive in the competitive online market. One of the key challenges for a new business is the lack of initial trust between the eretailer and the consumer

Strategies for Building Brand Equity for Unfamiliar Companies

Although widely used, existing brand equity models make implicit assumptions about the existence of consumer’s prior brand knowledge, lacking in guidance for less established, unfamiliar brands to build brand equity. Thus, a brand equity process model specifically catering to unfamiliar brands is warranted. In building brand equity for unfamiliar brands, consumer’s risk perception is a crucial factor to consider. Without any previous encounter, consumers can more easily experience a heightened sense of perceived risk, stemming from uncertainties about the brand. Thus, this study proposes that forming the high impression of brand quality, leading to initial trust can play a critical role in alleviating this risk. With this, the study proposes a conceptual brand equity process model with a specific emphasis on developing methods to build quality perception of the brand, and empirically testing the model

Embedded System Performance Analysis for Implementing a Portable Drowsiness Detection System for Drivers

Drowsiness on the road is a widespread problem with fatal consequences; thus, a multitude of systems and techniques have been proposed. Among existing methods, Ghoddoosian et al. utilized temporal blinking patterns to detect early signs of drowsiness, but their algorithm was tested only on a powerful desktop computer, which is not practical to apply in a moving vehicle setting. In this paper, we propose an efficient platform to run Ghoddosian's algorithm, detail the performance tests we ran to determine this platform, and explain our threshold optimization logic. After considering the Jetson Nano and Beelink (Mini PC), we concluded that the Mini PC is the most efficient and practical to run our embedded system in a vehicle. To determine this, we ran communication speed tests and evaluated total processing times for inference operations. Based on our experiments, the average total processing time to run the drowsiness detection model was 94.27 ms for Jetson Nano and 22.73 ms for the Beelink (Mini PC). Considering the portability and power efficiency of each device, along with the processing time results, the Beelink (Mini PC) was determined to be most suitable. Also, we propose a threshold optimization algorithm, which determines whether the driver is drowsy or alert based on the trade-off between the sensitivity and specificity of the drowsiness detection model. Our study will serve as a crucial next step for drowsiness detection research and its application in vehicles. Through our experiment, we have determinend a favorable platform that can run drowsiness detection algorithms in real-time and can be used as a foundation to further advance drowsiness detection research. In doing so, we have bridged the gap between an existing embedded system and its actual implementation in vehicles to bring drowsiness technology a step closer to prevalent real-life implementation.Comment: 26 pages, 13 figures, 4 table