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The critical velocity is the minimum velocity blowing towards the fire seat in tunnels to reduce the length of back-layering to zero, and it has been extensively adopted in the design of longitudinal smoke control in tunnels. A new concept, i.e., sub-critical velocity, is proposed in lieu of critical velocity for longitudinally ventilated tunnels. The sub-critical velocity allows the presence of back-layering upstream of the fire, provided that the back-layering is kept above the heads of motorists, thus posing no detrimental impact on them during evacuation. Experiments with propane fires with heat release rates of 3.7–25.5 kW were conducted in a 1/20 reduced-scale model tunnel. Both the lengths and the heights of back-layering at varying HRRs and longitudinal velocities were studied. Subsequently, the relationship of critical velocity and sub-critical velocity were developed. The results showed that sub-critical velocity is around 45–60% of the critical velocity. The adoption of sub-critical velocity in the design of longitudinally ventilated tunnels not only significantly reduces the cost of fans to drive the airflow, but also minimizes the impact of ventilation on heat release rates.

Maintaining surveillance of emerging infectious diseases presents challenges for monitoring their transmission and burden. Incomplete observation of infections and imperfect diagnosis reduce the observed sizes of transmission chains relative to their true sizes. Previous studies have examined the effect of incomplete observation on estimates of pathogen transmission and burden. However, each study assumed that, if observed, each infection was correctly diagnosed. Here, I leveraged principles from branching process theory to examine how misdiagnosis could contribute to bias in estimates of transmission and burden for emerging infectious diseases. Using the zoonotic Plasmodium knowlesi malaria as a case study, I found that, even when assuming complete observation of infections, the number of misdiagnosed cases within a transmission chain for every correctly diagnosed case could range from 0 (0 – 4) when R0 was 0.1 to 86 (0 – 837) when R0 was 0.9. Data on transmission chain sizes obtained using an imperfect diagnostic could consistently lead to underestimates of R0, the basic reproduction number, and simulations revealed that such data on up to 1,000 observed transmission chains was not powered to detect changes in transmission. My results demonstrate that misdiagnosis may hinder effective monitoring of emerging infectious diseases and that sensitivity of diagnostics should be considered in evaluations of surveillance systems.

The Chinese Accelerator Driven Sub-critical system (C-ADS) Injector-I is designed and constructed by the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences (CAS) in Beijing, China. The test cryomodule (TCM), housing two 325 MHz spoke cavities and two solenoids and operating at 2 K, has been designed, assembled and commissioned since the beginning of 2012. The C-ADS Injector-I linac with the TCM successfully accelerated the proton beam to 3.68 MeV with the peak current of 10.1 mA in pulse mode. It is the world’s first prototype of spoke cavity cryomodule with beam, and is an important step in the qualification of the cryomodule before series productions. This paper describes the detail of the design, operation and thermal performances of the prototype cryomodule. The analysis takes into account the heat loads of the main components (support posts, multilayer insulation and cavities) at various cryogenic temperature levels. The estimated heat loads of the cryomodule have been compared with the available experimental measurements, and the cryogenic deformations by simulation is verified by the experimental measurements by the wire position monitors (WPMs). The operation experiences including the cool down, alignment and heat load measurement are reported.

Various faults may simultaneously occur in a rotor dynamic system. It is crucial to detect and monitor these faults to ensure the safe operation of machinery. Usually, vibration response is utilized for fault diagnosis; however, the identification process becomes more challenging when multiple faults exhibit similar symptoms in the vibration response. In this paper, the vibrational transient response of a cracked rotor is analyzed in the presence of unbalance and coupling misalignment. The study focuses on investigating the possibility, advantages and limitations of using the sub-critical startup response in solving the fault identification problem. Numerical simulations using finite element modeling and experimental investigations are carried out for different individual and multi-fault conditions. Various factors are taken into consideration, including sub-critical limit speed, crack parameters, unbalance parameters and misalignment severity. Numerical and experimental investigations showed that the sub-critical transient response is suitable for the fault detection and diagnosis of the simultaneously existing faults studied. Compared to the critical response, the sub-critical response is more informative and each fault shows a unique feature that can be extracted without the need for sophisticated post signal processing. The study provides useful insights on the interaction between the various fault effects on the vibratory response and presents a simple method for condition monitoring of industrial equipment.

Unsteady multi-hole probe measurements are conducted to investigate the near wake of a circular cylinder at Reynolds numbers which vary between 3000 and 10000. Besides the pressure measurements, data with a triple-wire probe are recorded to validate the multi-hole probe results. The streamwise and lateral velocity components and their higher order statistical moments are investigated. Furthermore, frequency spectra of the velocity components are shown. Experimental results of the unsteady multi-hole probe demonstrate a good match with the hot-wire results as well as numerical and experimental data from the literature.

Recently, we reported that 83% indium was recovered from CF glass and 10% from TFT glass of LCD panel wastes using sub-critical water at 360 °C. In the present work, in order to increase the recovery of indium in the form of indium tin oxide (ITO) and to reduce the reaction temperature, the effect of basic materials and their concentrations in sub-critical water on its recovery were tested. The basic materials were NaOH, KOH, Na2CO3, diethyl amine, Ca(OH)2 and NH3. NaOH showed the largest recovery of indium from both CF and TFT glasses and reduced the reaction temperature. Treatment for only 5 min resulted in an outstanding indium recovery of 95% at 220 °C from TFT glass and 99% at 160 °C from CF glass. After the treatment, both TFT and CF glasses became transparent. ITO did not dissolve in the liquid-phase but remained in the solid organic multi-layers that were separated from the TFT and CF glasses by the sub-critical water reaction. These organic multi-layers were readily recovered by filtration. Since no indium dissolved in the liquid-phase, this recovery method is superior to others such as acid dissolution and ion-exchange. The optimum requirement of NaOH concentration and reaction time for indium recovery was 0.1 N and 5 min, respectively. The present result showed a significant improvement in indium recovery compared to our previous result without NaOH. Thus, sub-critical water in the presence of NaOH is highly feasible for the recovery of indium from TFT and CF glasses.

A new 1D model using the real gas property is proposed to predict ejector performance at critical and sub-critical operational modes, while most previous 1D models usually used the ideal gas property and only predicted ejector performance at critical mode operation. Constant pressure mixing is assumed to occur inside the constant area section of the ejector at critical and sub-critical mode operation, and the effectiveness of the model is verified against experimental data. The results show that the proposed model accurately predicts ejector performance over all ranges of operation. The 1D model is a useful tool for predicting ejector performance within larger refrigeration cycle models.

The nature and extent of hydrogen bonding in water has been scrutinized for decades, including how it manifests in optical properties. Here we report vacuum ultraviolet absorption spectra for the lowest-lying electronic state of subcritical and supercritical water. For subcritical water, the spectrum redshifts considerably with increasing temperature, demonstrating the gradual breakdown of the hydrogen-bond network. Tuning the density at 381 °C gives insight into the extent of hydrogen bonding in supercritical water. The known gas-phase spectrum, including its vibronic structure, is duplicated in the low-density limit. With increasing density, the spectrum blueshifts and the vibronic structure is quenched as the water monomer becomes electronically perturbed. Fits to the supercritical water spectra demonstrate consistency with dimer/trimer fractions calculated from the water virial equation of state and equilibrium constants. Using the known water dimer interaction potential, we estimate the critical distance between molecules (ca. 4.5 Å) needed to explain the vibronic structure quenching., The link between hydrogen bonding and the optical properties of water has been debated for many years, but not fully understood. Here, the authors report vacuum ultraviolet absorption spectra for subcritical and supercritical water, providing insight into the electronic structure of water and its relation to hydrogen bonding.

This paper proposes a new 1D model to predict ejector performance at critical and sub-critical operational modes, while most previous 1D models have only predicted ejector performance at critical mode operation. Constant pressure mixing is assumed to occur inside the constant area section of the ejector at critical and sub-critical mode operation, and the effectiveness of the model is verified against four sets of experimental data that include different working fluids and geometries. The results show that the proposed model accurately predicts ejector performance over all ranges of operation, and is a useful tool for predicting ejector performance within larger refrigeration cycle models.

Crystallinity of PLA is an important factor that affects its processability, mechanical strength, biodegradability, and service temperature. In this paper crystallization of PLA in solid state foaming process was studied in two main aspects: gas sorption in saturation stage, and heating as well as stretching in foaming stage. During CO2 saturation the equilibrium crystallinity jumped from 9.7% at 2 MPa to 26.4% at 3 MPa CO2 pressure. Further increases in saturation pressure did not increase the crystallinity. In the gas sorption stage of the process, it was found that the crystallization reached equilibrium at approximately the same time as the gas sorption reached equilibrium. Within the range of 2 to 5 MPa saturation pressures and 60 to 100°C foaming temperatures, a maximum crystallinity of 26.8% was observed in the foamed PLA. Crystallinity increased with the extent of cell-wall stretching during the foaming process.

Substance liable to self heat and spontaneously ignite under storage or transportation conditions can be a serious fire hazard in several industries. In order to estimate if, under specific storage conditions, a substance will dangerously self heat up to ignition, it is necessary to have knowledge of several thermochemical properties of the substance itself. Among this properties, one of the most relevant is the overall activation energy of the exothermic reactions that are responsible of the internal heat generation. In this short communication it will be discussed the possibility to retrieve the value of the overall activation energy from oven heating experiments conducted at temperature below the critical temperature of the sample, taking as an example a set of experimental data retrieved for commercially available charcoal briquettes.

Tin and transparent glass substrate were efficiently recovered from color filter (CF) and thin-film transistor (TFT) glasses in LCD panel wastes using sub-critical water (sub-CW) at various treatment temperatures and reaction time. Treatment for 5 min using sub-CW added with NaOH resulted in a 95% recovery of tin from CF and TFT glasses. The tin oxide did not liquify in the liquid phase instead stayed in the organic multi-layers, which exfoliated together from the CF glass and TFT glass. This is a huge advantage because the organic multi-layers were readily separated by sub-CW and tin was recovered by filtration with ease. Transparent and clean glass was also recovered from LCD panel waste. The amount of tin oxide recovered depended on the sub-CW reaction temperature, reaction time and NaOH concentration. Treatment of smaller CF glass improved the recovery of tin. With this advance, we have showed that sub-CW method is technically feasible for tin oxide recovery in LCD waste.

In this study single droplet dynamics for a Newtonian droplet in a Newtonian matrix have been observed in a controlled complex flow field. The mixed flow conditions, i.e. a combination of shear and extension, were applied using a newly designed eccentric cylinder device, and deforming droplets were visualised using optical microscopy. The experimental results on droplet deformation and orientation are compared with the predictions of the phenomenological Maffetone-Minale model. The model predictions are obtained by using the transient form of the model and incorporating a flow type parameter that accounts for the relative amount of shear and elongational effects. For all the sub-critical flows considered here, good agreement was found between the model predictions and the experimental data.

A series of design scoping and fuel cycle studies for sub-critical fast transmutation reactors driven by tokamak fusion neutron sources has been carried out to determine if the requirements on the tokamak neutron sources are compatible with the fusion physics and technology design database that will exist after the operation of ITER and to determine if there is a significant advantage in fuel cycle flexibility due to sub-critical operation that would justify the additional cost and complexity of a fusion neutron source. The fast reactor technologies are based on reactor concepts being developed in the DoE Generation-IV and Advanced Fuel Cycle initiatives.

In the HAT cycle, as the absolute humidity of the moist combustion gas increases, the performance of the turbine will also change. In this paper, one model to calculate the thermodynamic properties of the moist combustion gas is introduced, and another model to calculate the performance of the turbine is formulated based on the equations of one dimensional flow. Using these models with the geometric parameters of the turbine fixed, at the design working condition, the performance of the turbine is calculated and analyzed for different absolute humidities. Finally, some conclusions about the turbine performance are presented.

This study shows the changes in transmembrane pressure in a membrane bioreactor (MBR) operating at a constant flux and in well-defined biological conditions. Despite the initial choice of filtration conditions at sub-critical flux, gradual fouling is seen to develop in membrane material which, after long periods of experimentation without intermediary membrane regeneration, proves to be hydraulically irreversible. Thus a single parameter model was set up, whose value could be derived from monitoring the changes in transmembrane pressure. It works on the hypothesis that the open surface is reduced due to a successive blocking of membrane pores. The development of this model has shown that, despite operating conditions held at constant flux, an increase occurs in the rate of circulation in the pores which remain open, which may reach critical local filtration conditions, resulting in the formation of deposits which are reversible but induce an abrupt change in transmembrane pressure.

In order to qualify the PATRC code, data were collected from the Edwin I. Hatch Unit 2 (Cycle 16) BWR nuclear power plant using the standard core monitoring system. By matching control rod position vs. time two periods of time were noted where there were no control rod movements, yet there was a coincidental decrease of the average source range detector reading simultaneously with an increase of the reactor moderator temperature. By evaluating the data, sub-critical moderator temperature coefficients were obtained which compared well with PATRC calculations performed in this report. By reproducing similar reactor conditions during the start-up of future cycles, the moderator temperature coefficient can be determined before achieving criticality, such information can be valuable for reactor operators.

Hydrostatic testing is the principle method for managing stress corrosion cracking (SCC) of natural gas transmission pipelines. The long-term benefit of such testing relates to the stress margin between testing and operation and the effect of overstress on the surviving population of sub critical defects. This research was initiated to understand the response of these subcritical cracks of varied dimensions to hydrostatic testing in typical soil electrolytes that are conducive to SCC. More than 10 laboratory hydrostatic simulations have been conducted in this investigation. The results obtained provide insight into such issues as whether there will be crack advances during the hydrostatic test and the effect of hydrostatic testing on the subsequent growth of surviving cracks during service.Copyright © 2006 by ASME

The reliability test of an electron cyclotron resonance ion source developed for accelerator driven sub-critical system is carried out in China Institute of Atomic Energy. A unique technique to improve the reliability is adopted. The source is operated for more than 200 h at 75 keV, 100 mA extracted hydrogen current, while 2 beam trips are recorded in the period, and uninterrupted operation time is about 150 h. The experimental result is described.

Fermentations with recombinant bacteria containing run-away plasmids are typically operated alternately above and below a critical temperature. To minimize the risks of run away reactions, it is preferable to keep the high temperature periods as short as possible. In this study the possibility of sustained low temperature (sub-critical) operation in a suitably non-homogeneous broth is analyzed. Fluid dispersion is used as a measure of non-homogeneity.

While in most observations on the helium II film, transport at the critical velocity has been studied, the present paper describes observations of film transfer at velocities less than the critical. Three different methods of investigation have been employed. The first is an analogue of an electrical circuit embodying a current-potential measurement on a superconductor. The second method uses as indicator the formation of bulk liquid out of a film which passes over a surface of varying perimeter. In these two methods film transfer occurs from a higher to a lower meniscus of bulk liquid. In the third method film transfer is initiated by the introduction of a thermal gradient and transfer rates under varying heat input are studied. The experiments show conclusively that, similar to the phenomenon of superconductivity, below a critical velocity, flow of helium through the film is completely free of dissipation. The third method has been used to determine the heat of transport for the film, and these experiments are described and discussed in an Appendix.

An ultrasonic technique was developed to detect and characterize laser damage in critical optics . During normal usage, sub critical flaws induced by high laser fluence can grow to critical size and potentially can cause unanticipated failure of the optics. This ultrasonic technique monitors the optic in situ and provides a quick, reliable way to quantify the location, number and, ultimately, the size of defects that may initiate and grow during firing of the laser.

BS>Calculations were made of the criticality of Pu(NO/sub 3/)/sub 4/ solutions in two subcritical arrays. An extrapolation of the inverse multiplication curve for a shielded array of 5-in.-dia. tanks of stainless steel indicated that the 5 tanks could be of infinite length and remain subcritical. Results for the 30-in.-dia. Rasching-ring-filled stainless steel tank indicated that the vessel would not be critical at any height. (M.C.G.)