Atomic clocks based on laser-cooled atoms are widely used as primary frequency standards. Deploying such cold atom clocks (CACs) in space is foreseen to have many applications. Here we present tests of a CAC operating in space. In orbital microgravity, the atoms are cooled, trapped, launched, and finally detected after being interrogated by a microwave field using the Ramsey method. Perturbing influences from the orbital environment on the atoms such as varying magnetic fields and the passage of the spacecraft through Earth’s radiation belt are also controlled and mitigated. With appropriate parameters settings, closed-loop locking of the CAC is realized in orbit and an estimated short-term frequency stability close to 3.0 × 10−13τ−1/2 has been attained. The demonstration of the long-term operation of cold atom clock in orbit opens possibility on the applications of space-based cold atom sensors.

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Online shopping has progressed from having consumers passively browse through the webpages of online stores to having them proactively engage in communication dialogues with the sellers themselves via live chat. Modern-day consumers can now directly contact online sellers and inquire about the products they intend to purchase through the live chat medium available in the webpages of online stores, such as Taobao.com. In this study, the conceptual framework of motivation, opportunity, and ability was extended to understand the antecedents of using live chat and to lengthen such an understanding on one's eventual intention to transact on the website from the trust-oriented perspective. A total of 222 online consumers of Taobao.com were surveyed, and their responses validated the proposed conceptual model and confirmed the research hypotheses. Results of the investigation indicated that perceived information asymmetry and fears of seller opportunism, encapsulated under motivation dimension, and perceived personal expertise, which manifests ability dimension, significantly influence the use of live chat by consumers. The results further demonstrated that live chat use positively affects the perceived interactivity of consumers, thereby increasing their intention to transact. The influence of live chat use on the perceived interactivity of consumers and its effect on one's intention to transact online are negatively moderated by the trust of consumers in a seller. The findings contribute to our understanding communication services for e-commerce in general and to the realization of real-time communication technology in particular.

Background: Local, state, and federal governments have started exploring the potential of crowdfunding in transforming conventional financing methods used previously to fund public projects and services. While crowdfunding has been applied to improve government financing methods in recent years, little is known about how this new model can be extended and applied in international collaboration among governmentincentivized projects. Methods: In this paper, we explores what roles crowdfunding can play as a financial intermediary to support government-incentivized multinational projects in the context of the One-Belt, One-Road initiative.

a b s t r a c tThe critical cavitating flow in liquid jet pumps under operating limits is investigated in this paper. Measurements on the axial pressure distribution along the wall of jet pumps indicate that two-phase critical flow occurs in the throat pipe under operating limits. The entrained flow rate and the distribution of the wall pressure upstream lowest pressure section does not change when the outlet pressure is lower than a critical value. A liquid-vapor mixing shockwave is also observed under operating limits. The wave front moves back and forth in low frequency around the position of the lowest pressure. With the measured axial wall pressures, the Mach number of the two-phase cavitating flow is calculated. It's found that the maximum Mach number is very close to 1 under operating limits. Further analysis infers a cross-section where Mach number approaches to 1 near the wave front. Thus, the liquid-vapor mixture velocity should reach the local sound velocity and resulting in the occurrence of operating limits.