The Utility of Nanocomposites in Fire Retardancy

Nanocomposites have been shown to significantly reduce the peak heat release rate, as measured by cone calorimetry, for many polymers but they typically have no effect on the oxygen index or the UL-94 classification. In this review, we will cover what is known about the processes by which nanocomposite formation may bring this about. Montmorillonite will be the focus in this paper but attention will also be devoted to other materials, including carbon nanotubes and layered double hydroxides. A second section will be devoted to combinations of nanocomposite formation with conventional (and unconventional) fire retardants. The paper will conclude with a section attempting to forecast the future

D−DˉD-\bar{D} mixing constraints on FCNC with a non-universal Z′Z^\prime

The BaBar and Belle collaborations have recently reported evidence for $D^0-\bar D^0$ mixing. This measurement provides the first significant constraint on FCNC in the up-quark sector for non-universal $Z^\prime$ models. Attributing the observed $D-\bar D$ mixing to new physics, we comment on the resulting rare $D$ and $t$ decays. We also show that a CP violating semileptonic asymmetry as large as $\sim 30$ is allowed by the experimental results.Comment: RevTex, 10 pages, 1 figure. Several typoes correcte

Time, Tense, & Rationality

In this thesis I try to advance our understanding of the nature of time. In particular I defend the idea that there is an objective difference between the past, the present, and the future; a metaphysical tense. This is in opposition to the idea that these distinctions merely mark an aspect of our perspective on entities in time. I argue that tensed beliefs – beliefs that go hand-in-hand with tensed language – are essential to our lives as rational animals. Firstly, they are essential to our practices of providing reasons for action and acting for reasons. Secondly, they are essential for our lives as emotional animals whose emotions are appropriately responsive to the world. Perry has argued that indexical – including tensed – beliefs are essential for actions. In order to attend my meeting, it is not enough that I know that it is at 2pm, I must also know that it is now 1:55pm. Examining Perry’s argument I show that its proper conclusion is that tensed and first-personal beliefs are necessary for rational actions. I argue that reasons are facts (not belief/desire complexes or intensional entities). Further, the rationality of an action derives solely from these reasons, so that when an agent is not mistaken their action is rational purely insofar as it is done for a reason that justifies it. This means that beliefs are required for rational actions only to the extent that they provide an awareness of reasons and thereby enable an action. A proper understanding of rational action thus enables me to say that if an action must involve one belief rather than another in order to be rational, this must be because the former belief involves an awareness of a reason, hence fact, that the latter does not. Combining this with the proper conclusion of Perry’s argument we can say that tensed beliefs are required in the place of any tenseless beliefs in rational actions, and therefore must involve an awareness of facts that the latter cannot capture. Given that our actions are by and large rational, it follows there are facts captured by tensed beliefs not captured by tenseless beliefs. There is a metaphysical tense. Prior has argued that some emotions involve tensed beliefs and Cockburn has furthered this to show that the appropriateness of some emotions depends upon these beliefs. It is inappropriate to grieve a future death or fear a past danger. I show that the appropriateness of emotions stems from the reasons they are felt for and that these reasons are revealed by the beliefs involved in these emotions. This enables me to argue that if an emotion must involve one belief rather than another to be appropriate, then this can only be because the former belief captures a reason that the latter does not. In combination with Prior/Cockburn’s conclusion I am thus able to argue, analogously to the case of rational actions, that if there are emotions which must involve tensed beliefs to be appropriate and there are examples of appropriate such emotions, then metaphysical tense is real. My thesis thus derives a conclusion about the nature of time from our nature as rational animals. These arguments also have implications for a proper understanding of first-personal indexicals, which must now be recognized to pick out facts not captured by non-first-personal language. The former of these conclusions has been famously attacked by McTaggart, and the latter by Wittgenstein, and so I will also say something to rebut these criticisms. My arguments also have implications for certain issues surrounding the cognitive significance of co-referring names/natural kind terms which I will show to be unproblematic

A 58 nW ECG ASIC With Motion-Tolerant Heartbeat Timing Extraction for Wearable Cardiovascular Monitoring

An ASIC for wearable cardiovascular monitoring is implemented using a topology that takes advantage of the electrocardiogram's (ECG) waveform to replace the traditional ECG instrumentation amplifier, ADC, and signal processor with a single chip solution. The ASIC can extract heartbeat timings in the presence of baseline drift, muscle artifact, and signal clipping. The circuit can operate with ECGs ranging from the chest location to remote locations where the ECG magnitude is as low as 30 μV. Besides heartbeat detection, a midpoint estimation method can accurately extract the ECG R-wave timing, enabling the calculations of heart rate variability. With 58 nW of power consumption at 0.8 V supply voltage and 0.76 mm[superscript 2] of active die area in standard 0.18 μm CMOS technology, the ECG ASIC is sufficiently low power and compact to be suitable for long term and wearable cardiovascular monitoring applications under stringent battery and size constraints.MIT Medical Electronic Device Realization Cente

A Universal Framework for Holographic MIMO Sensing

This paper addresses the sensing space identification of arbitrarily shaped continuous antennas. In the context of holographic multiple-input multiple-output (MIMO), a.k.a. large intelligent surfaces, these antennas offer benefits such as super-directivity and near-field operability. The sensing space reveals two key aspects: (a) its dimension specifies the maximally achievable spatial degrees of freedom (DoFs), and (b) the finite basis spanning this space accurately describes the sampled field. Earlier studies focus on specific geometries, bringing forth the need for extendable analysis to real-world conformal antennas. Thus, we introduce a universal framework to determine the antenna sensing space, regardless of its shape. The findings underscore both spatial and spectral concentration of sampled fields to define a generic eigenvalue problem of Slepian concentration. Results show that this approach precisely estimates the DoFs of well-known geometries, and verify its flexible extension to conformal antennas

A new simple form of quark mixing matrix

Although different parametrizations of quark mixing matrix are mathematically equivalent, the consequences of experimental analysis may be distinct. Based on the triminimal expansion of Kobayashi-Maskawa matrix around the unit matrix, we propose a new simple parametrization. Compared with the Wolfenstein parametrization, we find that the new form is not only consistent with the original one in the hierarchical structure, but also more convenient for numerical analysis and measurement of the CP-violating phase. By discussing the relation between our new form and the unitarity boomerang, we point out that along with the unitarity boomerang, this new parametrization is useful in hunting for new physics.Comment: 10 pages, 1 figure, final version for journal publicatio

Provably Efficient Adaptive Scheduling for Parallel Jobs

Scheduling competing jobs on multiprocessors has always been an important issue for parallel and distributed systems. The challenge is to ensure global, system-wide efficiency while offering a level of fairness to user jobs. Various degrees of successes have been achieved over the years. However, few existing schemes address both efficiency and fairness over a wide range of work loads. Moreover, in order to obtain analytical results, most of them require prior information about jobs, which may be difficult to obtain in real applications. This paper presents two novel adaptive scheduling algorithms -- GRAD for centralized scheduling, and WRAD for distributed scheduling. Both GRAD and WRAD ensure fair allocation under all levels of workload, and they offer provable efficiency without requiring prior information of job's parallelism. Moreover, they provide effective control over the scheduling overhead and ensure efficient utilization of processors. To the best of our knowledge, they are the first non-clairvoyant scheduling algorithms that offer such guarantees. We also believe that our new approach of resource request-allotment protocol deserves further exploration. Specifically, both GRAD and WRAD are O(1)-competitive with respect to mean response time for batched jobs, and O(1)-competitive with respect to makespan for non-batched jobs with arbitrary release times. The simulation results show that, for non-batched jobs, the makespan produced by GRAD is no more than 1.39 times of the optimal on average and it never exceeds 4.5 times. For batched jobs, the mean response time produced by GRAD is no more than 2.37 times of the optimal on average, and it never exceeds 5.5 times.Singapore-MIT Alliance (SMA

Preventing Cracking of Anodized Coatings

Anodized coatings have been used as optical and thermal surfaces in spacecraft. Particulate contamination from cracked coatings is a concern for many applications. The major cause for the cracking is the difference in the coefficient of thermal expansion between the oxide coatings and the aluminum substrate. The loss of water when the coating is exposed to a vacuum also could induce cracking of the coating. Hot-water sealing was identified as the major cause for the cracking of the coatings because of the large temperature change when the parts were immersed in boiling water and the water was absorbed in the coating. when the hot-water sealing process was eliminated, the cracking resistance of the anodized coatings was greatly improved. Also, it was found that dyed black coatings were more susceptible than clear coatings to cracking during thermo-vacuum cyclings