Human-centred design: An emergent conceptual model

(Human-centred design: an emergent conceptual module by Zhang T and Dong H) Understanding human needs and how design responds to human needs are essential for human-centred design (HCD). By combining Maslow’s hierarchy of needs model and Küthe’s “design and society” model, this paper proposes a conceptual model of human-centred design which marries psychology and sociology in investigating the relationship between design and human needs. The study reveals a tendency that design evolution responds to the hierarchy of human needs. Nowadays design tends to care for more levels of human needs

Quantum filtering for multiple measurements driven by fields in single-photon states

In this paper, we derive the stochastic master equations for quantum systems driven by a single-photon input state which is contaminated by quantum vacuum noise. To improve estimation performance, quantum filters based on multiple-channel measurements are designed. Two cases, namely diffusive plus Poissonian measurements and two diffusive measurements, are considered.Comment: 8 pages, 6 figures, submitted for publication. Comments are welcome

Possible DDˉD\bar{D} and BBˉB\bar{B} Molecular states in a chiral quark model

We perform a systematic study of the bound state problem of $D\bar{D}$ and $B\bar{B}$ systems by using effective interaction in our chiral quark model. Our results show that both the interactions of $D\bar{D}$ and $B\bar{B}$ states are attractive, which consequently result in $I^G(J^{PC})=0^+(0^{++})$ $D\bar{D}$ and $B\bar{B}$ bound states.Comment: arXiv admin note: substantial text overlap with arXiv:1204.395

Distributed Opportunistic Scheduling for MIMO Ad-Hoc Networks

Distributed opportunistic scheduling (DOS) protocols are proposed for multiple-input multiple-output (MIMO) ad-hoc networks with contention-based medium access. The proposed scheduling protocols distinguish themselves from other existing works by their explicit design for system throughput improvement through exploiting spatial multiplexing and diversity in a {\em distributed} manner. As a result, multiple links can be scheduled to simultaneously transmit over the spatial channels formed by transmit/receiver antennas. Taking into account the tradeoff between feedback requirements and system throughput, we propose and compare protocols with different levels of feedback information. Furthermore, in contrast to the conventional random access protocols that ignore the physical channel conditions of contending links, the proposed protocols implement a pure threshold policy derived from optimal stopping theory, i.e. only links with threshold-exceeding channel conditions are allowed for data transmission. Simulation results confirm that the proposed protocols can achieve impressive throughput performance by exploiting spatial multiplexing and diversity.Comment: Proceedings of the 2008 IEEE International Conference on Communications, Beijing, May 19-23, 200

Distributed Opportunistic Scheduling For Ad-Hoc Communications Under Noisy Channel Estimation

Distributed opportunistic scheduling is studied for wireless ad-hoc networks, where many links contend for one channel using random access. In such networks, distributed opportunistic scheduling (DOS) involves a process of joint channel probing and distributed scheduling. It has been shown that under perfect channel estimation, the optimal DOS for maximizing the network throughput is a pure threshold policy. In this paper, this formalism is generalized to explore DOS under noisy channel estimation, where the transmission rate needs to be backed off from the estimated rate to reduce the outage. It is shown that the optimal scheduling policy remains to be threshold-based, and that the rate threshold turns out to be a function of the variance of the estimation error and be a functional of the backoff rate function. Since the optimal backoff rate is intractable, a suboptimal linear backoff scheme that backs off the estimated signal-to-noise ratio (SNR) and hence the rate is proposed. The corresponding optimal backoff ratio and rate threshold can be obtained via an iterative algorithm. Finally, simulation results are provided to illustrate the tradeoff caused by increasing training time to improve channel estimation at the cost of probing efficiency.Comment: Proceedings of the 2008 IEEE International Conference on Communications, Beijing, May 19-23, 200

Improving the security of quantum direct communication with authentication

Two protocols of quantum direct communication with authentication [Phys. Rev. A {\bf 73}, 042305 (2006)] are recently proposed by Lee, Lim and Yang. In this paper we will show that in the two protocols the authenticator Trent should be prevented from knowing the secret message of communication. The first protocol can be eavesdropped by Trent using the the intercept-measure-resend attack, while the second protocol can be eavesdropped by Trent using single-qubit measurement. To fix these leaks, I revise the original versions of the protocols by using the Pauli-Z operation $\sigma_z$ instead of the original bit-flip operation $X$. As a consequence, the protocol securities are improved.Comment: Any suggestion,comment or help is welcome