29,113 research outputs found

    Capacity of a Class of Deterministic Relay Channels

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    The capacity of a class of deterministic relay channels with the transmitter input X, the receiver output Y, the relay output Y_1 = f(X, Y), and a separate communication link from the relay to the receiver with capacity R_0, is shown to be C(R_0) = \max_{p(x)} \min \{I(X;Y)+R_0, I(X;Y, Y_1) \}. Thus every bit from the relay is worth exactly one bit to the receiver. Two alternative coding schemes are presented that achieve this capacity. The first scheme, ``hash-and-forward'', is based on a simple yet novel use of random binning on the space of relay outputs, while the second scheme uses the usual ``compress-and-forward''. In fact, these two schemes can be combined together to give a class of optimal coding schemes. As a corollary, this relay capacity result confirms a conjecture by Ahlswede and Han on the capacity of a channel with rate-limited state information at the decoder in the special case when the channel state is recoverable from the channel input and the output.Comment: 17 pages, submitted to IEEE Transactions on Information Theor

    Student Veterans/Service Members' Engagement in College and University Life and Education

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    Since the passage of the Post-9/11 Veterans Educational Assistance Act of 2008, also known as the Post-9/11 GI Bill, the enrollment of active-duty service members and veterans in American colleges and universities has increased substantially. According to the Department of Veterans Affairs, more than three-quarters of a million veterans have used their earned benefit to enroll in postsecondary courses. In response to the influx of veteran student enrollment, a group of higher education associations and veterans' organizations collaborated in 2009 and 2012 on a study that asked college and university administrators whether their institutions had geared up campus programs and services specifically designed to support the unique needs of veterans.1 The results indicated that administrators had indeed increased support levels, sometimes by quite significant margins.But how do student veterans/service members perceive their experiences at higher education institutions? To date, there is little or no information to assess whether the efforts by institutions to provide targeted programs and services are helpful to the veterans and service members enrolled in colleges and universities. Similarly, not much is known about the transition to postsecondary education from military service experienced by student veterans/service members, or whether these students are engaged in both academic programs and college and university life to their fullest potential. In this context, this issue brief explores student veteran/service member engagement in postsecondary education. The brief utilizes data from the 2012 National Survey of Student Engagement (NSSE), an annual survey of students enrolled in four-year universities, to assess how student veterans/service members perceive their integration on campus.A key finding is that student veterans/servicemembers are selective about the campus life and academic activities in which they invest their time. Student veterans/service members are morelikely to be first-generation students -- the first in their families to attend a college or university -- and older than nonveteran/civilian students; they therefore tend to have responsibilities outside of higher education that put constraints on their time.Student veterans/service members report placing greater emphasis on academic areas that they find essential for academic progress than on college and university life and activities -- academic or otherwise -- that are not essential for success in the courses in which they are enrolled. Student veterans/ service members are less likely to participate in co curricular activities, and they dedicate less time to relaxing and socializing than nonveteran/ civilian students

    State Amplification

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    We consider the problem of transmitting data at rate R over a state dependent channel p(y|x,s) with the state information available at the sender and at the same time conveying the information about the channel state itself to the receiver. The amount of state information that can be learned at the receiver is captured by the mutual information I(S^n; Y^n) between the state sequence S^n and the channel output Y^n. The optimal tradeoff is characterized between the information transmission rate R and the state uncertainty reduction rate \Delta, when the state information is either causally or noncausally available at the sender. This result is closely related and in a sense dual to a recent study by Merhav and Shamai, which solves the problem of masking the state information from the receiver rather than conveying it.Comment: 9 pages, 4 figures, submitted to IEEE Trans. Inform. Theory, revise

    Quantum Key Distribution with Blind Polarization Bases

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    We propose a new quantum key distribution scheme that uses the blind polarization basis. In our scheme the sender and the receiver share key information by exchanging qubits with arbitrary polarization angles without basis reconciliation. As only random polarizations are transmitted, our protocol is secure even when a key is embedded in a not-so-weak coherent-state pulse. We show its security against the photon number splitting attack and the impersonation attack.Comment: Security has been improved upon referee's comment. 4 pages and 2 figure

    Sub-band level-assisted photoconduction in epitaxial BiFeO3 films

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    Sub-band level assisted conduction mechanisms are well known in the field of semiconducting materials. In this work, we explicitly show the validity of such a mechanism in the multiferrroic material BiFeO3 (BFO). Our study is based on two different systems of epitaxial thin films of BFO, relaxed and strained. By analyzing the spectral distribution of the photoresponse from both the systems, the role of the sub-band levels in the photoconductive phenomena becomes evident. Additionally, the influence of epitaxial strain on the trapping activity of these levels is also observed. A model is proposed by taking into account the reversal of the role of a sub-band gap level, i.e., from a trapping to a ground state

    Complete BFT Embedding of Massive Theory with One- and Two-form Gauge Fields

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    We study the constraint structure of the topologically massive theory with one- and two-form fields in the framework of Batalin-Fradkin-Tyutin embedding procedure. Through this analysis we obtain a new type of Wess-Jumino action with novel symmetry, which is originated from the topological coupling term, as well as the St\"uckelberg action related to the explicit gauge breaking mass terms from the original theory.Comment: 22 pages, no figures, references adde
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