Mixing and transient interface condensation of a liquid hydrogen tank

Experiments were conducted to investigate the effect of axial jet-induced mixing on the pressure reduction of a thermally stratified liquid hydrogen tank. The tank was nearly cylindrical, having a volume of about 0.144 cu m with 0.559 m in diameter and 0.711 m long. A mixer/pump unit, which had a jet nozzle outlet of 0.0221 m in diameter was located 0.178 m from the tank bottom and was installed inside the tank to generate the axial jet mixing and tank fluid circulation. The liquid fill and jet flow rate ranged from 42 to 85 percent (by volume) and 0.409 to 2.43 cu m/hr, respectively. Mixing tests began with the tank pressure ranging from 187.5 to 238.5 kPa at which the thermal stratification results in 4.9 to 6.2 K liquid sub cooling. The mixing time and transient vapor condensation rate at the liquid-vapor interface are determined. Two mixing time correlations, based on the thermal equilibrium and pressure equilibrium, are developed. Both mixing time correlations are expressed as functions of system and buoyancy parameters and compared well with other experimental data. The steady state condensation rate correlation of Sonin et al. based on steam-water data is modified and expressed as a function of jet subcooling. The limited liquid hydrogen data of the present study shows that the modified steady state condensation rate correlation may be used to predict the transient condensation rate in a mixing process if the instantaneous values of jet sub cooling and turbulence intensity at the interface are employed

Perceived Factors Affecting the Integration-Responsiveness Framework: An Analysis from Chinese Multinationals Operating in Australia

This study extends quantitative and conceptual studies that have clarified and assessed the underlying factors influencing multinational corporations (MNCs) international business strategy choices relating to global integration and local responsiveness with the use of cross–level and in-depth interviews. Top management perceptions from nine Chinese MNCs (CMNCs) with operations in Australia are detailed and it is argued a contingency approach tends to prevail within firms with organisational, industrial, and environmental contingencies predominating

The interplay of managerial and non-managerial controls, institutional work, and the coordination of laterally dependent hospital activities

This is the author accepted manuscript. The final version is available from Emerald via the DOI in this record.Purpose The purpose of this paper is to explore two hospital departments, one of which is laterally dependent on the other to function, but which are subject to distinct vertical managerial controls. This complexity in vertical–lateral relations generates tension amongst the hospital’s senior managers and a perception of coordination difficulties. However, this paper shows how the interplay between managerial and non-managerial controls, plus important employee “work”, moderates tension and facilitates day-to-day lateral coordination at the patient-facing level. Design/methodology/approach This is a case-study, relying mostly on the findings of semi-structured interviews. Theoretically, the paper draws from previous insights on inter-organisational relations (but informing the focus on intra-organisational coordination) and an “institutional work” perspective. Findings Consistent with much extant literature, this paper reveals how non-managerial controls help to moderate tensions that could emerge from the coercive use of managerial controls. However, the authors also show a maintained influence and flexibility in the managerial controls at patient-facing levels, as new circumstances unfold. Research limitations/implications The findings of this paper could generalise neither all laterally dependent spaces in hospitals nor patterns across different hospitals. The authors recommend future research into the dynamics and interaction of managerial and non-managerial controls in other complex settings, plus focus on the purposeful work of influential agents. Originality/value The paper has two primary contributions: extending our knowledge of the interplay between managerial and non-managerial controls inside complex organisations, where non-managerial controls reinforce rather than displace managerial controls, and highlighting that it is seldom just controls per se which “matter”, but also agents’ purposeful actions that facilitate coordination in complex organisations

QYMSYM: A GPU-Accelerated Hybrid Symplectic Integrator That Permits Close Encounters

We describe a parallel hybrid symplectic integrator for planetary system integration that runs on a graphics processing unit (GPU). The integrator identifies close approaches between particles and switches from symplectic to Hermite algorithms for particles that require higher resolution integrations. The integrator is approximately as accurate as other hybrid symplectic integrators but is GPU accelerated.Comment: 17 pages, 2 figure

GPUVerify: A Verifier for GPU Kernels

We present a technique for verifying race- and divergence-freedom of GPU kernels that are written in mainstream ker-nel programming languages such as OpenCL and CUDA. Our approach is founded on a novel formal operational se-mantics for GPU programming termed synchronous, delayed visibility (SDV) semantics. The SDV semantics provides a precise definition of barrier divergence in GPU kernels and allows kernel verification to be reduced to analysis of a sequential program, thereby completely avoiding the need to reason about thread interleavings, and allowing existing modular techniques for program verification to be leveraged. We describe an efficient encoding for data race detection and propose a method for automatically inferring loop invari-ants required for verification. We have implemented these techniques as a practical verification tool, GPUVerify, which can be applied directly to OpenCL and CUDA source code. We evaluate GPUVerify with respect to a set of 163 kernels drawn from public and commercial sources. Our evaluation demonstrates that GPUVerify is capable of efficient, auto-matic verification of a large number of real-world kernels

A subarcsecond near-infrared view of massive galaxies at z > 1 with Gemini Multiconjugate Adaptive Optics

We present images taken using the Gemini South Adaptive Optics Imager (GSAOI) with the Gemini Multiconjugate Adaptive Optics System (GeMS) in three 2 arcmin$^2$ fields in the Spitzer Extragalactic Representative Volume Survey. These GeMS/GSAOI observations are among the first $\approx 0.1^{''}$ resolution data in the near-infrared spanning extragalactic fields exceeding $1.5^{\prime}$ in size. We use these data to estimate galaxy sizes, obtaining results similar to those from studies with the Hubble Space Telescope, though we find a higher fraction of compact star forming galaxies at $z>2$. To disentangle the star-forming galaxies from active galactic nuclei (AGN), we use multiwavelength data from surveys in the optical and infrared, including far-infrared data from Herschel, as well as new radio continuum data from the Australia Telescope Compact Array and Very Large Array. We identify ultraluminous infrared galaxies (ULIRGs) at $z \sim 1-3$, which consist of a combination of pure starburst galaxies and Active Galactic Nuclei (AGN)/starburst composites. The ULIRGs show signs of recent merger activity, such as highly disturbed morphologies and include a rare candidate triple AGN. We find that AGN tend to reside in hosts with smaller scale sizes than purely star-forming galaxies of similar infrared luminosity. Our observations demonstrate the potential for MCAO to complement the deeper galaxy surveys to be made with the James Webb Space Telescope.Comment: 20 pages, AJ, in pres

Multi-Stage Programming for GPUs in Modern C++ using PACXX

Writing and optimizing programs for high performance on systems with GPUs remains a challenging task even for expert programmers. One promising optimization technique is to evaluate parts of the program upfront on the CPU and embed the computed results in the GPU code allowing for more aggressive compiler optimizations. This technique is known as multi-stage programming and has proven to allow for significant performance benefits. Unfortunately, to achieve such optimizations in current GPU programming models like OpenCL, programmers are forced to manipulate the GPU source code as plain strings, which is error-prone and type-unsafe. In this paper we describe PACXX - a GPU programming approach using modern C++ standards, with the convenient features like type deduction, lambda expressions, and algorithms from the standard template library (STL). Using PACXX, a GPU program is written as a single C++ program, rather than two distinct host and kernel programs. We extend PACXX with an easy-to-use and type-safe API for multi-stage programming avoiding the pitfalls of string manipulation. Using just-in-time compilation techniques, PACXX generates efficient GPU code at runtime. Our evaluation shows that using PACXX allows for writing multi-stage code easier and safer than currently possible. Using two detailed application studies we show that multi-stage programming can significantly outperform equivalent non-staged programs. Furthermore, we show that PACXX generates code with performance comparable to industrial-strength OpenCL compilers