Synthetic gauge potential and effective magnetic field in a Raman medium undergoing molecular modulation

We theoretically demonstrate non-trivial topological effects for a probe field in a Raman medium undergoing molecular modulation processes. The medium is driven by two non-collinear pump beams. We show that the angle between the pumps is related to an effective gauge potential and an effective magnetic field for the probe field in the synthetic space consisting of a synthetic frequency dimension and a spatial dimension. As a result of such effective magnetic field, the probe field can exhibit topologically-protected one-way edge state in the synthetic space, as well as Landau levels which manifests as suppression of both diffraction and sideband generation. Our work identifies a previously unexplored route towards creating topological photonics effects, and highlights an important connection between topological photonics and nonlinear optics

Sideband generation of transient lasing without population inversion

We suggest a method to generate coherent short pulses by generating a frequency comb using lasing without inversion in the transient regime. We use a universal method to study the propagation of a pulse in various spectral regions through an active medium that is strongly driven on a low-frequency transition on a time scale shorter than the decoherence time. The results show gain on the sidebands at different modes can be produced even if there is no initial population inversion prepared. Besides the production of ultra-short pulse this frequency comb may have applications towards making short-wavelength or Tera-hertz lasers

Exploring the bicycle planning culture and implementation challenges : case studies of Hamburg and Wuhan

Many cities are suffering from problems caused by extensive car use. Cycling, as a mode of transport, can be helpful to reduce emissions, improve public health, and increase traffic efficiency. However, transport planning in many cities has been focused on motorized transport and overlooked cyclists. To shape a supportive urban environment for cyclists, a number of important questions with regard to bicycle planning are not yet fully understood, for instance, the relationship between the built environment and cycling, the barriers to implementing pro-cycling policies, and the bicycling planning culture in growing cities. This thesis is structured around four objectives. The first objective is to investigate the relationship between the objectively measured built environment and active transportation (walking and cycling for transport) among adults. A systematic literature review of journal articles from four databases was conducted. The systematic literature search identified 51 articles published between 2005 and 2017. From the 51 articles, 12 built environment factors were extracted. The results show that most studies examined factors related to walkability and accessibility. Street connectivity shows a convincing positive relationship with both walking and cycling for transport. However, neighborhood aesthetics and access to destinations show inconsistent relationships. In addition, choosing suitable geographic units and measurement of active transportation is necessary to reduce the mismatch in the relationships. The second objective is to identify barriers to implementing pro-cycling policies. While many studies have recommended policy interventions to promote cycling, not enough research has focused on the barriers to implementing pro-cycling policies. This study took an in-depth look at Hamburg, which started a major cycling promotion in 2008 with a range of interventions. According to expert interviews and literature surveys, the results show that the major barriers are physical (lack of enough physical space), political and institutional (lack of political support and the evaluation of travel behavior), and social and cultural (people’s reluctance to give up on-street car parking space). Suggestions for overcoming the barriers are proposed. The third objective is to explore the bicycle planning culture in a growing city. A case study was conducted in Wuhan, China. Data were collected through semi-structured expert interviews and a questionnaire survey. The exploration of bicycle planning culture was guided by the culturized planning model. The results indicate that bicycle planning practices in Wuhan are more often based on planners’ individual judgments with informal rules, which sometimes do not assign cycling a legitimate role. While the principles are targeting a cycling-friendly street design, the actual improvement of the cycling infrastructure is selective and fragmented. Planners have positive perceptions of cycling but doubts about bicycle commuting. Planners are inclined to consider bicycle transport as a complement to public transport. The fourth objective is to compare bicycle planning in different contexts. Bicycle planning culture in Hamburg and Wuhan are compared by using the culturized planning model. The results indicate that although cycling is gaining increasing attention in both cities, the two cities show significant differences in the level of professionalism of bicycle planning. Hamburg has a more systematic bicycle plan, a more detailed implementation strategy, and stronger political support. Cycling is already an important part of the transport system of Hamburg; however, it plays a marginal role in that of Wuhan, where there are more ambivalent and negative attitudes towards cycling. In general, this thesis contributes to a better understanding of bicycle planning with regard to different aspects, including the built environment, policy implementation and planning culture. To further investigate the relationship between the built environment and cycling for transport, more longitudinal studies and more studies in different contexts are needed. For an effective policy implementation, more research is necessary to explore how to gain stronger political support and how to create space for cycling infrastructure in space-scarce cities. Also, the role of cycling for transport in large growing cities should be further explored

Two birds with one stone: Goal conflict handling and its effect on well-being

A tourist’s journey is often shaped by the pursuit of diverse and sometimes conflicting goals. In this study, we investigate how tourists handle conflicting goals during their travels. Drawing upon life history theory, we have developed and tested a conceptual model that examines how life history strategies (LHS, fast vs. slow) influence goal management approaches (highlighting vs. balancing) and their subsequent impact on tourist well-being. Through a combination of surveys, field and lab experiments, and a meta-analysis, our research reveals that when confronted with goal conflicts, tourists with a fast LHS tend to prefer a highlighting approach, while those with a slow LHS gravitate towards a balancing approach, with perceived deservingness serving as a mediator in this relationship. Moreover, matching (vs. mismatching) LHS with goal management enhances overall well-being. These findings offer valuable insights for both theoretical advancement and practical management in tourism

Influence of brand on Chinese consumers’ behaviours in Automobile choice: An investigation on Chinese customers’ buying attitudes towards domestic and foreign car brands

In recent years, branding as a powerful tool to influence consumer behaviors has becoming a hot topic in the marketing literature. But few studies focus on the influence of brands on Chinese consumers’ behaviors, especially their buying attitudes in the automobile market. This dissertation attempts to investigate the influence of brand on Chinese consumers’ behaviors in automobile choice and their buying attitudes towards domestic and foreign brands. The author chose the qualitative research as the most appropriated research approach due to the nature of the topic. The interview was employed to collect the primary data. Ten interviewees attended the interview. And they were selected by using the convenience sampling technique. Finally, the author analyzed the data from the interviews based on the grounded theory. The author generated and analyzed the findings according to accomplish the four objectives of the study. Based on the findings, the author recommended that the Chinese car marketers should do more efforts of enhancing brand awareness and build the brand consciousness. Moreover, the Chinese car makers and marketers should pay more attention to look after and maintain the existing customers. In addition, the Chinese car makers should try their best to change the image in consumers’ minds by improving the quality and changing the brand position. Key words: Brand equity, Symbolic Values, Global brands, local brands, Country-of-origin, consumer ethnocentris

Exploration with Global Consistency Using Real-Time Re-integration and Active Loop Closure

Despite recent progress of robotic exploration, most methods assume that drift-free localization is available, which is problematic in reality and causes severe distortion of the reconstructed map. In this work, we present a systematic exploration mapping and planning framework that deals with drifted localization, allowing efficient and globally consistent reconstruction. A real-time re-integration-based mapping approach along with a frame pruning mechanism is proposed, which rectifies map distortion effectively when drifted localization is corrected upon detecting loop-closure. Besides, an exploration planning method considering historical viewpoints is presented to enable active loop closing, which promotes a higher opportunity to correct localization errors and further improves the mapping quality. We evaluate both the mapping and planning methods as well as the entire system comprehensively in simulation and real-world experiments, showing their effectiveness in practice. The implementation of the proposed method will be made open-source for the benefit of the robotics community

Extreme subradiance from two-band Bloch oscillations in atomic arrays

Atomic arrays provide an important quantum optical platform with photon-mediated dipoledipole interactions, which can be engineered to realize key applications in quantum information processing. A major obstacle for such application is the fast decay of the excited states. By controlling two-band Bloch oscillations in an atomic array under external magnetic field, here we show that exotic subradiance can be realized and maintained at a time scale upto 12 orders of magnitude larger than the spontaneous decay time in atomic arrays with the finite size. The key finding is to show a way for preventing the wavepacket of excited states scattering into the dissipative zone inside the free space light cone, which therefore leads to the excitation staying at a subradiant state for extremely long decay time. We show that such operation can be achieved by introducing a spatially linear potential from external magnetic field in atomic arrays and then manipulating interconnected two-band Bloch oscillations along opposite directions. Our results also point out the possibility of controllable switching between superradiant and subradiant states, which leads to potential applications in quantum storage.Comment: 6 pages, 3 figure