Cold Shell Research Articles

Reduction of the deceleration phase to mitigate the negative effect of hydrodynamic instabilities in direct-drive ICF implosions

In the deceleration phase of an Inertial Confinement Fusion capsule implosion Rayleigh–Taylor hydrodynamic instability can affect or even quench the ignition and thermonuclear burn wave propagation. This instability tends to mix the inner hot plasma with the cold and dense plasma shell providing a mixing layer where nuclear fusion reactions are inhibited. The 1D hydrodynamics code Multi-IFE has been used to simulate the implosion of a direct-drive high-gain laser-capsule design and the temporal evolution of the average radius and thickness of the mixing layer have been estimated. To mimic the effect of the reduced reaction rate, the fuel reactivity in the mixing layer is artificially set to zero thus inhibiting the burn wave propagation throughout it nullifying the energy gain. In order to overcome this negative effect, secondary short and powerful laser pulse is added, shortening this way the deceleration phase, which in turn reduces the thickness of the mixing layer. A study has been carried out to identify the optimal secondary laser pulse that recovers the high energy gain.

Cloud Formation by Supernova Implosion

The deposition of energy and momentum by supernova explosions has been subject to numerous studies in the past few decades. However, while there has been some work that focused on the transition from the adiabatic to the radiative stage of a supernova remnant (SNR), the late radiative stage and merging with the interstellar medium (ISM) have received little attention. Here, we use three-dimensional, hydrodynamic simulations, focusing on the evolution of SNRs during the radiative phase, considering a wide range of physical explosion parameters ( nH,ISM∈0.1,100cm−3 and ESN∈1,14×1051erg ). We find that the radiative phase can be subdivided in four stages: A pressure-driven snowplow phase, during which the hot overpressurized bubble gas is evacuated and pushed into the cold shell; a momentum-conserving snowplow phase that is accompanied by a broadening of the shell; an implosion phase where cold material from the back of the shell is flooding the central vacuum; and a final cloud phase, during which the imploding gas is settling as a central, compact overdensity. The launching timescale for the implosion ranges from a few 100 kyr to a few Myr, while the cloud formation timescale ranges from a few to about 10 Myr. The highly chemically enriched clouds can become massive (M cl ∼ 103–104 M ⊙) and self-gravitating within a few Myr after their formation, providing an attractive, novel pathway for supernova-induced star and planet formation in the ISM.

Development of a Cost Normalization Framework for Healthcare Facilities Cost Elements

Healthcare facilities (HCFs) are complex building structures that are becoming more challenging with ever-changing codes and regulations. Previously completed projects become a basis for future guidance regarding costs and scope. A robust normalization framework to assess previously completed projects with today’s costs and location will benefit various stakeholders. The current study provides a complete picture for normalizing the overall project cost and phase cost by life cycle and HCF cost elements. This study aims to develop a cost normalization approach tailored to HCF-specific cost elements to extend the normalization framework for the overall project cost. Further, the researchers developed a distinct framework for normalizing the effect of shell space on the normalization of Total Installed Cost (TIC) to establish fixed cost adjustment rates for cold and warm shell spaces in HCFs, which can increase the accuracy of cost normalization of the overall project cost. This study identified an appropriate set of cost indices for normalizing HCF cost elements using publicly available indices. The cost elements identified for normalization included HCF-specific and Construction Specifications Institute Master Format (CSIMF) cost elements for assigning individual normalization procedures. This study provides individual and unique approaches for normalizing all identified cost elements, such as mechanical, concrete, etc. The initial framework was evaluated through a case study analysis that developed into the proposed approach built upon the collaborative efforts of academic researchers and industry experts. This study introduced shell space cost adjustment rates for warm and cold shell spaces to further develop a space normalization framework. This paper addresses the challenges of normalizing HCF project costs using the breakdown of HCF cost elements. Moreover, the paper provides the HCF’s overall cost normalization approach, emphasizing cost elements that allow accurate comparisons between various HCFs for early scope and cost guidance.

The Combination of Architectural Art and Humanization

Art is a broad term that encompasses various virtual and practical art disciplines, of which architecture is a major category. Within the broad category of art, it seems that every small category can react with each other, creating works of higher artistic quality for the world. It is precisely because art has always upheld this characteristic that it has been continuously upgraded by people in recent years. In the process of creation, many art scholars have found that both art and architecture need to be combined with people to be better accepted by society. Film art needs to be appreciated by audiences, music art needs to be listened to by people, painting art needs to be viewed by people, installation art needs to be photographed by people, and architectural art needs to be felt by users rather than a cold empty shell. Therefore, this article describes the connection between contemporary art and architecture, which can be related to human nature. Any kind of art returns to its essence in order to reflect a phenomenon that exists in mass society, and it is displayed to the public to trigger people’s resonance and reflection. Since ancient times, the relationship between architecture and people has been complementary. In the process of designing buildings, people integrate various artistic techniques to make them respond to the site and applicable people. The final design of the building also serves the users in the building, making them feel comfortable and more efficient in completing work and life. Therefore, the art of architecture is ultimately designed and thought around human nature. In recent years, tall buildings have sprung up in cities across China, and gradually every city has its own “CBD” and landmark buildings. However, what we see more often are some cold buildings, some buildings built for the purpose of volume rate and unique shape, which often only design the strange shape shell and then hand it over to the construction party, or low-level copies of master’s design works. These examples are often cold empty shells that cannot make the people living in them feel the warmth brought by the building. I think that there is a lack of artistic and user-oriented architecture in China, rather than focusing on mass production and copying. This may change the lifestyle and quality of life of the public, and realize the humanization of architecture from the perspective of architectural art.

Lightweight modular construction of school classrooms, reverberation time prediction versus field testing

Lightweight modular schools are in the early phases of being designed and constructed throughout NSW as part of Schools Infrastructure “Modern Methods of Construction (MMC).” This method proposes the use of CLT (Cross Laminated Timber) panels, timber floor and wall cassettes, and/or hybrid systems. Schools Infrastructure NSW has developed, along with PKA Acoustic Consulting’s acoustic input, the “Kit of Parts” catalogue which utilises predetermined set of components that can easily be assembled and constructed. The classroom layout is therefore defined and can be incorporated into the acoustic predictive model. Additionally, the absorption characteristics of lightweight constructions differ to conventional construction and therefore should be considered. This presentation discusses the significance of construction type and fitout finishes, by comparing predicted reverb times of modular lightweight classrooms with in-situ absorptive testing at various cold shell, warm shell, and completed fitout stages of a school classroom and open learning space.

A New Study on a Type Iax Stellar Remnant and its Probable Association with SN 1181

We report observations and modeling of the stellar remnant and presumed double-degenerate merger of Type Iax supernova Pa 30, which is the probable remnant of SN 1181 AD. It is the only known bound stellar SN remnant and the only star with Wolf–Rayet features that is neither a planetary nebula central star nor a massive Population I progenitor. We model the unique emission-line spectrum with broad, strong O vi and O viii lines as a fast stellar wind and shocked, hot gas. Non-LTE wind modeling indicates a mass-loss rate of ∼10−6 M ⊙ yr−1 and a terminal velocity of ∼15,000 km s−1, consistent with earlier results. O viii lines indicate shocked gas temperatures of T ≃ 4 MK. We derive a magnetic field upper limit of B < 2.5 MG, below earlier suggestions. The luminosity indicates a remnant mass of 1.0–1.65 M ⊙ with ejecta mass 0.15 ± 0.05 M ⊙. Archival photometry suggests the stellar remnant has dimmed by ∼0.5 mag over 100 yr. A low Ne/O < 0.15 argues against an O-Ne white dwarf in the merger. A cold dust shell is only the second detection of dust in an SN Iax and the first of cold dust. Our ejecta mass and kinetic energy estimates of the remnant are consistent with Type Iax extragalactic sources.

The interaction of supernova 2018evt with a substantial amount of circumstellar matter – An SN 1997cy-like event

ABSTRACT A rare class of supernovae (SNe) is characterized by strong interaction between the ejecta and several solar masses of circumstellar matter (CSM) as evidenced by strong Balmer-line emission. Within the first few weeks after the explosion, they may display spectral features similar to overluminous Type Ia SNe, while at later phase their observation properties exhibit remarkable similarities with some extreme case of Type IIn SNe that show strong Balmer lines years after the explosion. We present polarimetric observations of SN 2018evt obtained by the ESO Very Large Telescope from 172 to 219 d after the estimated time of peak luminosity to study the geometry of the CSM. The non-zero continuum polarization decreases over time, suggesting that the mass-loss of the progenitor star is aspherical. The prominent H α emission can be decomposed into a broad, time-evolving component and an intermediate-width, static component. The former shows polarized signals, and it is likely to arise from a cold dense shell (CDS) within the region between the forward and reverse shocks. The latter is significantly unpolarized, and it is likely to arise from shocked, fragmented gas clouds in the H-rich CSM. We infer that SN 2018evt exploded inside a massive and aspherical circumstellar cloud. The symmetry axes of the CSM and the SN appear to be similar. SN 2018evt shows observational properties common to events that display strong interaction between the ejecta and CSM, implying that they share similar circumstellar configurations. Our preliminary estimate also suggests that the circumstellar environment of SN 2018evt has been significantly enriched at a rate of ∼0.1 M⊙ yr−1 over a period of &amp;gt;100 yr.

Impact of the ERF on the structure and evolution of SNRs

ABSTRACT We carry out 1D hydrodynamical simulations of the evolution of a spherically symmetric supernova remnant (SNR) subject to an external radiation field (ERF) that influences the cooling and heating rates of the gas. We consider homogeneous media with ambient hydrogen number densities nH, 0 of 0.1 and 1 cm−3 permeated by an average radiation field including the cosmic microwave, extragalactic, and Galactic backgrounds, attenuated by an effective column density NH, eff from 1018 to 1021 cm−2. Our results may be classified into two broad categories: at low NH, eff, the ERF presents little absorption in the ultraviolet (ionizing) regime, and all the ’unshielded’ cases feature an equilibrium temperature Teq ∼ 7000 K below which the ambient gas cannot cool further. In this scenario, the SNR develops a nearly isothermal shock profile whose shell becomes thicker over time. At higher NH, eff, the ERF is heavily absorbed in the UV range, yielding a roughly constant heating function for temperatures ≲ 104 K. These ‘shielded’ cases develop a thin, cold and dense shell throughout their evolution. Energy and momentum injection to the medium do not change significantly between both scenarios, albeit luminosity is higher and more uniformly distributed over the shell for unshielded SNR.

A New Methodology for Predicting Brittle Fracture of Plastically Deformable Materials: Application to a Cold Shell Nosing Process.

The traditional theory of ductile fracture has limitations for predicting crack generation during a cold shell nosing process. Various damage criteria are employed to explain fracture and failure in the nose part of a cold shell. In this study, differences in microstructure among fractured materials and analysis of their surfaces indicated the occurrence of brittle fractures. The degree of “plastic deformation-induced embrittlement” (PDIE) of plastically deformable materials affects the likelihood of brittle fractures; PDIE can also decrease the strength in tension due to the Bauschinger effect. Two indicators of brittle fracture are presented, i.e., the critical value of PDIE and the allowable tensile strength (which in turn depends on the degree of PDIE or embrittlement-effective strain). When the maximum principal stress is greater than the latter and the PDIE is greater than the former, our method determines the likelihood of brittle fracture. This approach was applied to an actual cold shell nosing process, and the predictions were in good quantitative agreement with the experimental results.

Further development of the Xe laser plasma 11-nm radiation source – new data on laser energy absorption and spectroscopy

Absorption of the laser pulse energy in the plasma has been shown to change from 8.5% at irradiation of a gas-puff target with a beam narrow-focused onto a near-central area of the jet up to 65% at the wide defocused irradiation. An analysis of this phenomenon is based on a hypothesis that plasma density decays significantly during the 10ns laser pulse due to hydrodynamic expansion of the hot plasma. A similarity of the EUV (Extreme UltraViolet) intensity and the laser light absorption as functions of the laser beam diameter suggests a revision of the conventional idea of a strong EUV radiation self-absorption in a cold peripheral shell of the laser plasma whereas the high absorptivity of the laser radiation by the plasma looks like a major feature to gain high efficiency of an EUV source.

Choice of materials properties and of shell molds structure by investment models

The paper presents a mathematical model optimizing the choice of material and morphological structure of the shell mold (SM), which has the highest resistance to cracking when pouring liquid metal into it. To solve this problem, the theory of small elastoplastic deformations and the heat equation, as well as proven numerical methods, were used. The objective function min – max was constructed from control variables characterizing the properties of the molding material of the shell. The process of heating an axisymmetric shell mold was considered when pouring liquid metal into it. The resistance of the shell form was estimated by the stresses arising in it. An algorithm for solving this problem was compiled. Using numerical schemes and program complexes developed in previous studies, an algorithm for solving the optimization problem was constructed and the values of control variables were found in which the shell mold does not break even in the presence of a rigid process – pouring steel into a cold shell mold. Analysis of the influence of weight of each of the found parameters on the value of the constructed objective function is given. Using a mathematical experiment, the morphological structure of the shell mold was studied. The shell mold of five layers is considered. The corrected system of equations makes it possible to take into account the properties of the layers made of different materials. Calculations were performed when the layer of the shell mold from material found by optimization occupies different positions in its cross section. In this case, the remaining layers of the mold are made of traditional ceramics. The optimal location of this layer was found. It is shown that the presence of several layers with the found properties does not affect the increase in crack resistance of the shell mold.

Hot-electron deposition and implosion mechanisms within electron shock ignition**Project supported by the National Natural Science Foundation of China (Grant No. 11775203) and the Presidential Foundation of China Academy of Engineering Physics (Grant No. YZJJLX 2016007).

A hot-electron driven scheme can be more effective than a laser-driven scheme within suitable hot-electron energy and target density. In our one-dimensional (1D) radiation hydrodynamic simulations, 20× pressure enhancement was achieved when the ignitor laser spike was replaced with a 60-keV hot-electron spike in a shock ignition target designed for the National Ignition Facility (NIF), which can lead to greater shell velocity. Higher hot-spot pressure at the deceleration phase was obtained owing to the greater shell velocity. More cold shell material is ablated into the hot spot, and it benefits the increases of the hot-spot pressure. Higher gain and a wider ignition window can be observed in the hot-electron-driven shock ignition.

Fraunhofer-type signal for underwater measurement of copper sample using collinear long-short double-pulse laser-induced breakdown spectroscopy

The collinear long-short double-pulse laser-induced breakdown spectroscopy (long-shrot DP-LIBS) is used to detect the underwater copper sample. Fraunhofer-type signal is acquired with very short gate delay parameter, which is the first time to be reported that the collinear long-short DP-LIBS can generate Fraunhofer-type signal from underwater target. It is found that the early structure of underwater plasma is similar to the solar structure. According to the plasma image of early stage, a cold shell with low emission intensity is wrapped around a hot core with strong emission intensity. During early period, the continuum radiation from the hot core is absorbed by the copper atoms in plasma edge, causing Fraunhofer-type absorption at Cu I 324.754 nm and Cu I 327.396 nm. The experimental results show that the absorption intensity of Fraunhofer-type lines possesses a well signal stability in early stage. RSD% of signal is 1.5% with 10 ns delays and 5.3% with 30 ns delays at Cu I 324.754 nm, and RSD% is 2.7% with 10 ns delays and 3.3% with 30 ns delays at Cu I 327.396 nm. The present results sugget that the Fraunhofer-type signal generated by collinear long-short DP-LIBS is possible to be used for further underwater quantitative measurement.

Chemical and radiative transfer modeling of propylene oxide

Context.The recent identification of the first complex chiral molecule, propylene oxide (PrO), in space opens up a new window to further study the origin of homochirality on the Earth. There are some recent studies to explain the formation of PrO however additional studies on the formation of this species are needed for better understanding.Aims.We seek to prepare a complete reaction network to study the formation of propylene oxide in the astrophysically relevant conditions. Based on our results, a detailed radiative transfer modeling has been carried out to propose some more transitions that would potentially be targeted in the millimeter wave domain.Methods.A gas-grain chemical network was used to explain the observed abundance of PrO in a cold shell surrounding the high-mass star-forming region of Sgr B2. Quantum chemical calculations were employed to study various reaction parameters and to compute multiple vibrational frequencies of PrO.Results.To model the formation of PrO in the observed region, we considered a dark cloud model. Additionally, we used a model to check the feasibility of forming PrO in the hot core region. Some potential transitions in the millimeter wave domain are predicted that could be useful for the future astronomical detection. We used radiative transfer modeling to extract the physical condition that might be useful to know the properties of the source in detail. Moreover, we provided vibrational transitions of PrO, which could be very useful for the future detection of PrO by the upcomingJames WebbSpace Telescope.

Impact of Stark Shifts on the Radiation Cooling of Cu-Dominated Plasmas

We study the impact of Stark line shifts reported recently for Cu I transitions on the radiative cooling of Cu-dominated plasmas. The observed detuning in absorption between the hot core and cold shell of the arc leads to a reduction in radiation reabsorption compared to the case where Stark line shifts are neglected. Using a modeling based on a phenomenological treatment of the Stark line shift, we show that this reduction is below 2%.

Coordination on Industrial Load Control and Climate Control in Manufacturing Industry Under TOU Prices

Demand side management (DSM) can help promote the efficiency and reliability of a power system. However, the benefits of DSM in the manufacturing industry will be weakened if the interactions between industrial load control and climate control are not considered. For example, industrial load control may impact the indoor temperature and humidity, affecting climate control. This interaction may ultimately result in an unexpected deviation from the ideal DSM plan. Hence in this paper, coordinated industrial load control and climate control are investigated in a cold machine shell manufacturer under time-of-use prices. The interaction of industrial loads and climate control is modeled, and a model predictive control-based method is proposed to address forecast uncertainties. The objective of DSM is to minimize electricity costs meanwhile meeting the respective objectives of the industrial load control and climate control. Case studies have verified the above benefits for a cold machine shell manufacturer, and the results show that additional reductions in demand during peak hours can be achieved using the proposed method.

Ignition and pusher adiabat

In the last five years, large amounts of high quality data on inertial confinement fusion (ICF) experiments were produced at the National Ignition Facility (NIF). From this data we have significantly advanced our scientific understanding of the physics of thermonuclear (TN) ignition and identified critical issues that must be addressed to achieve a burning hotspot, such as implosion energetics, pusher adiabat, tamping effects, and confinement time. In this paper we present a review of recently developed TN ignition and implosion scaling theory (Cheng et al 2013 Phys. Rev. E 88 041101; Cheng et al 2014 Phys. Plasmas 21 10270) that characterizes the thermodynamic properties of the hotspot and the ignition criteria for ICF. We compare our theoretical predictions with NIF data and find good agreement between theory and experiments. We demonstrate the fundamental effects of the pusher adiabat on the energy partition between the cold shell and the hot deuterium–tritium (DT) gas, and thus on the integrated performance of ICF capsules. Theoretical analysis of NIF experiments (Cheng et al 2015 Phys. Plasmas 22 082704; Melvin et al 2015 Phys. Plasmas 22 022708; Cheng et al 2016 Phys. Plasmas 23 120702) and physical explanations of the discrepancies between theory, data, and simulations are presented. It is shown that the true experimental adiabat of the cold DT fuel can be inferred from neutron image data of a capsule implosion. We show that the ablator mix and preheat in the cold fuel can be estimated from the experimentally inferred hotspot mix. Finally, possible paths forward to reach higher yields at NIF implied by the theory are discussed.

Supplemental heating of conventional Inertial Confinement Fusion

We report a new ICF scheme whereby a capsule is imploded to near ignition conditions and subsequently flooded with hot electrons generated from a short-pulse laser- plasma interaction so as to heat the whole assembly by a few hundred eV. The cold dense shell pressure is increased by a larger factor than that of the hot spot at the capsule core, so that further heating and compression of the hot spot occurs. We suggest it may be possible to drive the capsule to ignition by the pressure augmentation supplied by this extra deposition of energy.

Luminous blue variables: An imaging perspective on their binarity and near environment

Context. Luminous blue variables (LBVs) are rare massive stars with very high luminosity. They are characterized by strong photo-metric and spectroscopic variability related to transient eruptions. The mechanisms at the origin of these eruptions is not well known. In addition, their formation is still problematic and the presence of a companion could help to explain how they form. Aims. This article presents a study of seven LBVs (about 20% of the known Galactic population), some Wolf-Rayet stars, and massive binaries. We probe the environments that surround these massive stars with near-, mid-, and far-infrared images, investigating potential nebula/shells and the companion stars. Methods. To investigate large spatial scales, we used seeing-limited and near diffraction-limited adaptive optics images to obtain a differential diagnostic on the presence of circumstellar matter and to determine their extent. From those images, we also looked for the presence of binary companions on a wide orbit. Once a companion was detected, its gravitational binding to the central star was tested. Tests include the chance projection probability, the proper motion estimates with multi-epoch observations, flux ratio, and star separations. Results. We find that two out of seven of LBVs may have a wide orbit companion. Most of the LBVs display a large circumstellar envelope or several shells. In particular, HD168625, known for its rings, possesses several shells with possibly a large cold shell at the edge of which the rings are formed. For the first time, we have directly imaged the companion of LBV stars.

Sensitivity of inertial confinement fusion hot spot properties to the deuterium-tritium fuel adiabat

We determine the dependence of key Inertial Confinement Fusion (ICF) hot spot simulation properties on the deuterium-tritium fuel adiabat, here modified by addition of energy to the cold shell. Variation of this parameter reduces the simulation to experiment discrepancy in some, but not all, experimentally inferred quantities. Using simulations with radiation drives tuned to match experimental shots N120321 and N120405 from the National Ignition Campaign (NIC), we carry out sets of simulations with varying amounts of added entropy and examine the sensitivities of important experimental quantities. Neutron yields, burn widths, hot spot densities, and pressures follow a trend approaching their experimentally inferred quantities. Ion temperatures and areal densities are sensitive to the adiabat changes, but do not necessarily converge to their experimental quantities with the added entropy. This suggests that a modification to the simulation adiabat is one of, but not the only explanation of the observed simulation to experiment discrepancies. In addition, we use a theoretical model to predict 3D mix and observe a slight trend toward less mixing as the entropy is enhanced. Instantaneous quantities are assessed at the time of maximum neutron production, determined dynamically within each simulation. These trends contribute to ICF science, as an effort to understand the NIC simulation to experiment discrepancy, and in their relation to the high foot experiments, which features a higher adiabat in the experimental design and an improved neutron yield in the experimental results.