Distributed Gaussian Processes

To scale Gaussian processes (GPs) to large data sets we introduce the robust Bayesian Committee Machine (rBCM), a practical and scalable product-of-experts model for large-scale distributed GP regression. Unlike state-of-the-art sparse GP approximations, the rBCM is conceptually simple and does not rely on inducing or variational parameters. The key idea is to recursively distribute computations to independent computational units and, subsequently, recombine them to form an overall result. Efficient closed-form inference allows for straightforward parallelisation and distributed computations with a small memory footprint. The rBCM is independent of the computational graph and can be used on heterogeneous computing infrastructures, ranging from laptops to clusters. With sufficient computing resources our distributed GP model can handle arbitrarily large data sets.Comment: 10 pages, 5 figures. Appears in Proceedings of ICML 201

Hierarchical Mixture-of-Experts Model for Large-Scale Gaussian Process Regression

We propose a practical and scalable Gaussian process model for large-scale nonlinear probabilistic regression. Our mixture-of-experts model is conceptually simple and hierarchically recombines computations for an overall approximation of a full Gaussian process. Closed-form and distributed computations allow for efficient and massive parallelisation while keeping the memory consumption small. Given sufficient computing resources, our model can handle arbitrarily large data sets, without explicit sparse approximations. We provide strong experimental evidence that our model can be applied to large data sets of sizes far beyond millions. Hence, our model has the potential to lay the foundation for general large-scale Gaussian process research

Secure Massive MIMO Communication with Low-resolution DACs

In this paper, we investigate secure transmission in a massive multiple-input multiple-output (MIMO) system adopting low-resolution digital-to-analog converters (DACs). Artificial noise (AN) is deliberately transmitted simultaneously with the confidential signals to degrade the eavesdropper's channel quality. By applying the Bussgang theorem, a DAC quantization model is developed which facilitates the analysis of the asymptotic achievable secrecy rate. Interestingly, for a fixed power allocation factor $\phi$, low-resolution DACs typically result in a secrecy rate loss, but in certain cases they provide superior performance, e.g., at low signal-to-noise ratio (SNR). Specifically, we derive a closed-form SNR threshold which determines whether low-resolution or high-resolution DACs are preferable for improving the secrecy rate. Furthermore, a closed-form expression for the optimal $\phi$ is derived. With AN generated in the null-space of the user channel and the optimal $\phi$, low-resolution DACs inevitably cause secrecy rate loss. On the other hand, for random AN with the optimal $\phi$, the secrecy rate is hardly affected by the DAC resolution because the negative impact of the quantization noise can be compensated for by reducing the AN power. All the derived analytical results are verified by numerical simulations.Comment: 14 pages, 10 figure

Steam Turbine High Axial Displacement due to Governor Actuator Filter Clog

Case StudiesThe governor actuator for a steam turbine was observed to be hunting and failed to maintain stable operating speed. The steam turbine is used to drive a centrifugal compressor for H2 service in a recycle loop. The extent of speed oscillating was exaggerating over time and caused excessive turbine axial movement. The unit was forced to shut down to prevent secondary damage due to turbine high axial movement. The steam turbine was overhauled approximately 9 months prior to the incident. Oil flushing was performed, lube oil was changed out and main oil filters were replaced as part of machinery overhaul scope. The main oil filter elements were inspected during troubleshooting of this event and were badly fouled with blackish substance. The governor actuators were inspected and the internal filters for the oil supply line were clogged with soft, blackish substance. Foulant analysis was performed using Energy Dispersive X-ray (EDX) which identified the main component to be Carbon. De- gassing tank oil was drained out and observed layer of blackish substance. EDX identified the main component to be identical to that found in main oil filter. Water sample from de-gassing tank bottom drain was tested and the pH was 3-4 (i.e. acidic). Further troubleshooting revealed that fine carbon particles were carried over from upstream and mixing with the process gas prior to the unit shut down for the compressor train overhaul. The presence of carbon particles had contaminated the seal oil and control oil circuit which then clogged up the actuator internal fine filters (~40um). This case study presents the unusual phenomenon, troubleshooting tools, recovery process and key learnings which provide user operating with similar service a reference

1,1′-Di-n-butyl-4,4′-bipyridinium 2.375-bromido-1.625-chloridocadmate

The title salt, (C18H26N2)[CdBr2.375Cl1.625], consists of non-inter­acting cations and tetra­hedral cadmate(II) anions. The halogen atoms are all disordered, the bromine components being in 0.9035 (17):0.0965 (17), 0.6581 (18):0.3419 (18), 0.5019 (19):0.4981 (19) and 0.6847 (19):0.3153 (18) ratios. The aromatic rings of the cation are twisted by 25.0 (1)°

Optimizing Survivorship Care Services for Asian Adolescent and Young Adult Cancer Survivors: A Qualitative Study.

Purpose: With an increasing focus on developing survivorship services tailored for adolescent and young adult (AYA) cancer survivors, incorporation of viewpoints from both survivors and health care professionals (HCPs) is important. This study aims to explore the perceptions of current and prospective survivorship services from both groups in Singapore to propose service design and delivery strategies. Methods: Focus group discussions with 23 AYA cancer survivors between the ages of 16 and 39 years at diagnosis and 18 HCPs were conducted in National Cancer Centre Singapore (NCCS) and Singapore Cancer Society (SCS). All focus group discussions were transcribed verbatim. Deductive thematic analysis was performed according to the components of a design thinking model: empathizing with AYA survivors, defining care gaps, proposing services, and implementation strategies. Results: AYA survivors preferred age-specific services that are aligned with their personal goals. Current survivorship care failed to address the needs of survivors' dependents (caregivers and children) and to consider the utility of each service temporally. Prospective services should clarify disease disclosure obligation in job search and introduce a care navigator. Key implementation strategies included (1) training HCPs on communication techniques with AYA, (2) selecting engagement platforms that complement survivors' information-seeking behavior, (3) improving outreach to survivors through appropriate branding and publicity, and (4) consolidating services from multiple providers. Conclusions: The design of survivorship care services for AYA survivors should be systematic in its conceptualization process and employ implementation strategies. The coordination of the wide spectrum of services warrants a concerted effort by cancer centers, community partners, and the government

Perceptions and Barriers of Survivorship Care in Asia: Perceptions From Asian Breast Cancer Survivors.

PurposeWith the long-term goal to optimize post-treatment cancer care in Asia, we conducted a qualitative study to gather in-depth descriptions from multiethnic Asian breast cancer survivors on their perceptions and experiences of cancer survivorship and their perceived barriers to post-treatment follow-up.MethodsTwenty-four breast cancer survivors in Singapore participated in six structured focus group discussions. The focus group discussions were voice recorded, transcribed verbatim, and analyzed by thematic analysis.ResultsBreast cancer survivors were unfamiliar with and disliked the term "survivorship," because it implies that survivors had undergone hardship during their treatment. Cognitive impairment and peripheral neuropathy were physical symptoms that bothered survivors the most, and many indicated that they experienced emotional distress during survivorship, for which they turned to religion and peers as coping strategies. Survivors indicated lack of consultation time and fear of unplanned hospitalization as main barriers to optimal survivorship care. Furthermore, survivors indicated that they preferred receipt of survivorship care at the specialty cancer center.ConclusionBudding survivorship programs in Asia must take survivor perspectives into consideration to ensure that survivorship care is fully optimized within the community

An asymmetric supercapacitor with excellent cycling performance realized by hierarchical porous NiGa2O4 nanosheets

Rational design of composition and electrochemically favorable structure configuration of electrode materials are highly required to develop high-performance supercapacitors. Here, we report our findings on the design of interconnected NiGa2O4 nanosheets as advanced cathode electrodes for supercapacitors. Rietveld refinement analysis demonstrates that the incorporation of Ga in NiO leads to a larger cubic lattice parameter that promotes faster charge-transfer kinetics, enabling significantly improved electrochemical performance. The NiGa2O4 electrode delivers a specific capacitance of 1508 F g−1 at a current density of 1 A g−1 with the capacitance retention of 63.7% at 20 A g−1, together with excellent cycling stability after 10000 charge–discharge cycles (capacitance retention of 102.4%). An asymmetric supercapacitor device was assembled by using NiGa2O4 and Fe2O3 as cathode and anode electrodes, respectively. The ASC delivers a high energy density of 45.2 Wh kg−1 at a power density of 1600 W kg−1 with exceptional cycling stability (94.3% cell capacitance retention after 10000 cycles). These results suggest that NiGa2O4 can serve as a new class cathode material for advanced electrochemical energy storage applications

The use of multiple displacement amplification to amplify complex DNA libraries

Complex libraries for genomic DNA and cDNA sequencing analyses are typically amplified using bacterial propagation. To reduce biases, large numbers of colonies are plated and scraped from solid-surface agar. This process is time consuming, tedious and limits scaling up. At the same time, multiple displacement amplification (MDA) has been recently developed as a method for in vitro amplification of DNA. However, MDA has no selection function for the removal of ligation multimers. We developed a novel method of briefly introducing ligation reactions into bacteria to select single insert DNA clones followed by MDA to amplify. We applied these methods to a Gene Identification Signatures with Paired-End diTags (GIS-PET) library, which is a complex transcriptome library created by pairing short tags from the 5′ and 3′ ends of cDNA fragments together, and demonstrated that this selection and amplification strategy is unbiased and efficient