Virtual qubits, virtual temperatures, and the foundations of thermodynamics

We argue that thermal machines can be understood from the perspective of `virtual qubits' at `virtual temperatures': The relevant way to view the two heat baths which drive a thermal machine is as a composite system. Virtual qubits are two-level subsystems of this composite, and their virtual temperatures can take on any value, positive or negative. Thermal machines act upon an external system by placing it in thermal contact with a well-selected range of virtual qubits and temperatures. We demonstrate these claims by studying the smallest thermal machines. We show further that this perspective provides a powerful way to view thermodynamics, by analysing a number of phenomena. This includes approaching Carnot efficiency (where we find that all machines do so essentially by becoming equivalent to the smallest thermal machines), entropy production in irreversible machines, and a way to view work in terms of negative temperature and population inversion. Moreover we introduce the idea of "genuine" thermal machines and are led to considering the concept of "strength" of work.Comment: v2: Published version. 15 pages, 8 figure

Media Presence and Inner Presence: The Sense of Presence in Virtual Reality Technologies

Abstract. Presence is widely accepted as the key concept to be considered in any research involving human interaction with Virtual Reality (VR). Since its original description, the concept of presence has developed over the past decade to be considered by many researchers as the essence of any experience in a virtual environment. The VR generating systems comprise two main parts: a technological component and a psychological experience. The different relevance given to them produced two different but coexisting visions of presence: the rationalist and the psychological/ecological points of view. The rationalist point of view considers a VR system as a collection of specific machines with the necessity of the inclusion \ud of the concept of presence. The researchers agreeing with this approach describe the sense of presence as a function of the experience of a given medium (Media Presence). The main result of this approach is the definition of presence as the perceptual illusion of non-mediation produced by means of the disappearance of the medium from the conscious attention of the subject. At the other extreme, there \ud is the psychological or ecological perspective (Inner Presence). Specifically, this perspective considers presence as a neuropsychological phenomenon, evolved from the interplay of our biological and cultural inheritance, whose goal is the control of the human activity. \ud Given its key role and the rate at which new approaches to understanding and examining presence are appearing, this chapter draws together current research on presence to provide an up to date overview of the most widely accepted approaches to its understanding and measurement

Technological advantage and market loss: Siemens and the X-ray machine business in Japan (1900–1960)

This paper focuses on the involvement of Siemens on the market for radiology equipment in Japan between 1900 and 1960 from a business history perspective. It explores why the German multinational was unable to keep its dominant position on the Japanese market in the interwar years, despite its technological competitiveness. In particular, it examines the strategic choices made by the firm (export, licensing, direct investment) in relation to the changing economic and technological environment, highlighting the importance, for foreign multinationals, of working together with national trading firms involved in the distribution of drugs and products for doctors, as the Japanese medical market was already well structured when the country opened up to the West. Four phases have been identified. At first, before World War I, German manufacturers of X-ray machines, especially Siemens, enjoyed a virtual monopoly in Japan and favored an export strategy. The political and technological shifts that occurred during the war (interruption of trade with Germany, development of the Coolidge X-ray tube by General Electric) led to a more competitive market in Japan. Siemens reorganized its involvement in this business via a contract signed with a domestic medical goods trade company, Goto Fuundo (1926). Yet this proved insufficient to overcome the competition, and Siemens finally decided to relocate some of its production facilities for X-ray machines in Japan by entering into a joint venture with Goto (1932). Relations between Siemens and Goto were severed by the war, and Goto tried until the 1950s to go it alone in this field but failed due to a lack of organizational capability. As for Siemens, it reverted to its export strategy approach, re-entering the market in the 1950s.Siemens, Goto Fuundo, X-ray machines, medical market

Technological advantage and market loss: Siemens and the X-ray machine business in Japan (1900-1960)

This paper focuses on the involvement of Siemens on the market for radiology equipment in Japan between 1900 and 1960 from a business history perspective. It explores why the German multinational was unable to keep its dominant position on the Japanese market in the interwar years, despite its technological competitiveness. In particular, it examines the strategic choices made by the firm (export, licensing, direct investment) in relation to the changing economic and technological environment, highlighting the importance, for foreign multinationals, of working together with national trading firms involved in the distribution of drugs and products for doctors, as the Japanese medical market was already well structured when the country opened up to the West. Four phases have been identified. At first, before World War I, German manufacturers of X-ray machines, especially Siemens, enjoyed a virtual monopoly in Japan and favored an export strategy. The political and technological shifts that occurred during the war (interruption of trade with Germany, development of the Coolidge X-ray tube by General Electric) led to a more competitive market in Japan. Siemens reorganized its involvement in this business via a contract signed with a domestic medical goods trade company, Goto Fuundo (1926). Yet this proved insufficient to overcome the competition, and Siemens finally decided to relocate some of its production facilities for X-ray machines in Japan by entering into a joint venture with Goto (1932). Relations between Siemens and Goto were severed by the war, and Goto tried until the 1950s to go it alone in this field but failed due to a lack of organizational capability. As for Siemens, it reverted to its export strategy approach, re-entering the market in the 1950s.Siemens, Goto Fuundo, X-ray machines, medical market

Moving in next door: Network flooding as a side channel in cloud environments

The final publication is available at http://link.springer.com/chapter/10.1007/978-3-319-48965-0_56Co-locating multiple tenants' virtual machines (VMs) on the same host underpins public clouds' affordability, but sharing physical hardware also exposes consumer VMs to side channel attacks from adversarial co-residents. We demonstrate passive bandwidth measurement to perform traffic analysis attacks on co-located VMs. Our attacks do not assume a privileged position in the network or require any communication between adversarial and victim VMs. Using a single feature in the observed bandwidth data, our algorithm can identify which of 3 potential YouTube videos a co-resident VM streamed with 66% accuracy. We discuss defense from both a cloud provider's and a consumer's perspective, showing that effective defense is difficult to achieve without costly under-utilization on the part of the cloud provider or over-utilization on the part of the consumer.We would like to acknowledge the MIT PRIMES program and thank in particular Dr. Slava Gerovitch and Dr. Srini Devadas for their support. We are also grateful to Boston University, the Hariri Institute, and the Massachusetts Open Cloud. This paper is based upon work supported by the National Science Foundation under Grants No. 1414119 and 1413920

Simplified cloud-oriented virtual machine management with MLN

System administrators are faced with the challenge of making their existing systems power-efficient and scalable. Although Cloud Computing is offered as a solution to this challenge by many, we argue that having multiple interfaces and cloud providers can result in more complexity than before. This paper addresses cloud computing from a user perspective. We show how complex scenarios, such as an on-demand render farm and scaling web-service, can be achieved utilizing clouds but at the same time keeping the same management interface as for local virtual machines. Further, we demonstrate that by enabling the virtual machine to have its policy locally instead of in the underlying framework, it can move between otherwise incompatible cloud providers and sites in order to achieve its goals more efficiently