Memories of Empire in Cold War Japan

Between 1895 and 1945 Japan assembled one of the largest empires in modern world history. It vanished abruptly in the summer of 1945 at the end of the Second World War, and seemed to leave no trace in public consciousness. Historians, too, have portrayed postwar Japan as characterized by a virtual erasure of the imperial past. This article draws on recent scholarship to argue that things were more complicated than that. While references to the imperial past indeed dwindled after about 1960, immediate forgetting did not exhaust the reactions by individuals and interest groups. Some social milieus experienced the dissolution of the empire much more profoundly than official discourse would suggest. Since the mid-1990s, Japan's imperial past has reemerged as a major field of historical inquiry and a more general concern in public debate. In this article I situate the dialectic of remembering and forgetting within larger processes and transformations of the postwar order in East Asia, in particular the American occupation and the emergence of the Cold War

Determining Dark Matter properties with a XENONnT/LZ signal and LHC-Run3 mono-jet searches

We develop a method to forecast the outcome of the LHC Run 3 based on the hypothetical detection of $\mathcal{O}(100)$ signal events at XENONnT. Our method relies on a systematic classification of renormalisable single-mediator models for dark matter-quark interactions, and is valid for dark matter candidates of spin less than or equal to one. Applying our method to simulated data, we find that at the end of the LHC Run 3 only two mutually exclusive scenarios would be compatible with the detection of $\mathcal{O}(100)$ signal events at XENONnT. In a first scenario, the energy distribution of the signal events is featureless, as for canonical spin-independent interactions. In this case, if a mono-jet signal is detected at the LHC, dark matter must have spin 1/2 and interact with nucleons through a unique velocity-dependent operator. If a mono-jet signal is not detected, dark matter interacts with nucleons through canonical spin-independent interactions. In a second scenario, the spectral distribution of the signal events exhibits a bump at non zero recoil energies. In this second case, a mono-jet signal can be detected at the LHC Run 3, dark matter must have spin 1/2 and interact with nucleons through a unique momentum-dependent operator. We therefore conclude that the observation of $\mathcal{O}(100)$ signal events at XENONnT combined with the detection, or the lack of detection, of a mono-jet signal at the LHC Run 3 would significantly narrow the range of possible dark matter-nucleon interactions. As we argued above, it can also provide key information on the dark matter particle spin.Comment: 17 pages, 8 figures, updated operator coefficients and figures, version accepted by PR

Perspectivas en Diálogo

En su nueva edición de 2021, Perspectivas en Diálogo ofrece a sus lectores un nuevo debate enfocado en la Historia Global como perspectiva de análisis histórico. En este caso, Juan Pablo Scarfi y Eduardo Zimmermann dialogan con Sebastian Conrad sobre su libro What Is Global History

Flashboiling atomization in nozzles for GDI engines

[EN] Flashboiling denotes the phenomenon of rapid evaporation and atomization at nozzles, which occurs when fluids are injected into ambient pressure below their own vapor pressure. It happens in gasoline direct injection (GDI) engines at low loads, when the cylinder pressure is low during injection due to the closed throttle valve. The fuel temperature at the same time approaches cylinder head coolant temperature due to the longer dwell time of the fuel inside the injector. Flash boiling is mainly beneficial for atomization quality, since it produces small droplet sizes and relative broad and homogenous droplet distributions within the spray. Coherently, the penetration depth normally decreases due to the increased aerodynamic drag. Therefore the thermal properties of injectors are often designed to reach flash boiling conditions as early as possible. At the same time, flash boiling significantly increases the risk of undesired spray collapsing. In this case, neighbouring jets converge and form a single jet. Due to the now concentrated mass, penetration depth is enhanced again and can lead to liner or piston wetting in addition to the overall diminished mixture formation. In order to understand the underlying physics, it is important to study the occurring phenomena flashboiling and jet-to-jet interacting i.e. spray collapsing separately. To this end, single hole injectors are built up to allow for an isolated investigation of flashboiling. The rapid expansion at the nozzle outlet is visualized with a microscopic high speed setup and the forces that lead to the characteristic spray expansion are discussed. Moreover, the results on the macroscopic spray in terms of penetration, cone angles and vapor phase are shown with a high speed Schlieren setup. Resulting droplet diameters and velocities are measured using LDA/PDA. As a result, we find a comprehensive picture of flash boiling. The underlying physics can be described and discussed for the specific case of high pressure injection at engine relevant nozzle geometries and conditions, but independently from neighbouring jets. These findings provide the basis to understand and investigate flashboiling and jet-to-jet interaction as distinct, but interacting subjects rather than a combined phenomenon.The authors would like to thank Continental for providing the experimental injectors used in this paper and Specialised Imaging for providing parts of the equipment used for the shown measurements. Additionally the authors gratefully acknowledge the financial support for parts of their work from the Erlangen Graduate School in Advanced Optical Technologies (SAOT) within the framework of the German Excellence Initiative by the German Research Foundation (DFG).Bornschlegel, S.; Conrad, C.; Eichhorn, L.; Wensing, M. (2017). Flashboiling atomization in nozzles for GDI engines. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat Politècnica de València. 321-328. https://doi.org/10.4995/ILASS2017.2017.4750OCS32132

Innovative Dam Monitoring Tools Based on Distributed Temperature Measurement

Distributed fibreoptic measurements contain a number of particular features. Even though they are nowadays used for strain measurements, actually the most interesting parameter to be monitored by distributed fibreoptic measurements in dams is temperature. Due to their enormous mass, large structures such as dams usually show very slow behaviour in terms of temperature changes. It is well known that temperature measurements have to be carried out in concrete dams in order to observe the development of the heat of hydration. Furthermore, seepage flows affect the temperature field within the dams and their foundations. The Distributed Fibre Optic Temperature DFOT measurement was identified to be ideally suited for monitoring the temperature fields of dams, both for leakage detection and for the observation of concrete temperatures. For almost one decade, DFOT measurement has proven to be a powerful tool to detect and locate leakage in hydraulic structures. Leakage detection by means of DFOT measurements has been typically implemented through two major approaches: the gradient method, which employs the temperature as a tracer to detect anomalies in the flow field; and the heat-up method, which allows detecting the presence and movement of water by evaluating the thermal response after external heat is induced. In the past years more and more DFOT projects are under progress. As for today, the DFOT measurement has to be considered as a state of the art tool in dam monitoring. Nevertheless, especially in the field of leakage detection, there is still an enormous potential to improve effectiveness. New additional applications will be developed and important parameters as the seepage velocity in soil material will be measured with DFOT technology in the future. Being robust and gaining a high density of in-situ information out of the dam, DFOT technology has to be considered as one of the key technologies in tomorrow’s dam monitoring

JJ-factors for self-interacting dark matter in 20 dwarf spheroidal galaxies

Dwarf spheroidal galaxies are among the most promising targets for indirect dark matter (DM) searches in $\gamma$-rays. The $\gamma$-ray flux from DM annihilation in a dwarf spheroidal galaxy is proportional to the $J$-factor of the source. The $J$-factor of a dwarf spheroidal galaxy is the line-of-sight integral of the DM mass density squared times $\langle \sigma_{\rm ann} v_{\rm rel} \rangle/(\sigma_{\rm ann} v_{\rm rel})_0$, where $\sigma_{\rm ann} v_{\rm rel}$ is the DM annihilation cross-section times relative velocity $v_{\rm rel}=|{\bf v}_{\rm rel}|$, angle brackets denote average over ${\bf v}_{\rm rel}$, and $(\sigma_{\rm ann} v_{\rm rel})_0$ is the $v_{\rm rel}$-independent part of $\sigma_{\rm ann} v_{\rm rel}$. If $\sigma_{\rm ann} v_{\rm rel}$ is constant in $v_{\rm rel}$, $J$-factors only depend on the DM space distribution in the source. However, if $\sigma_{\rm ann} v_{\rm rel}$ varies with $v_{\rm rel}$, as in the presence of DM self-interactions, $J$-factors also depend on the DM velocity distribution, and on the strength and range of the DM self-interaction. Models for self-interacting DM are increasingly important in the study of the small scale clustering of DM, and are compatible with current cosmological observations. Here we derive the $J$-factor of 20 dwarf spheroidal galaxies from stellar kinematic data under the assumption of Yukawa DM self-interactions. $J$-factors are derived through a profile Likelihood approach, assuming either NFW or cored DM profiles. We also compare our results with $J$-factors derived assuming the same velocity for all DM particles in the target galaxy. We find that this common approximation overestimates the $J$-factors by up to one order of magnitude. $J$-factors for a sample of DM particle masses, self-interaction coupling constants and density profiles are provided electronically, ready to be used in other projects.Comment: 10 pages, 3 figures and 2 table

Leveraging P2P systems to address the test scenario explosion problem

Modern software development is characterised by a strong customer focus and electronic delivery mechanisms which make it very easy for customers to buy and install a vendor’s software. However, it also makes it very easy for customers to buy and install software from competing vendors and as such it is more important than ever for deployed software to be as correct and bug-free as possible. Whilst certain types of testing can be done in the lab with a high degree of confidence that results will hold when the software is deployed in the wild, in reality software systems are subject to influence from whatever environment they end up being deployed in. Varying factors in customer environments can include operating systems, services packs, device drivers, network connectivity, resource usage by other software, and so on. Any variation or combination of these factors can lead to a situation where a system deviates from its expected behaviour. The problem is amplified even further on mobile devices whereby devices can move between different networks, interrupt apps for phone calls, have varying screen sizes, have user interference in the form of turning features on and o↵ to preserve battery power, vendor-specific operating system code, and so on. A conservative calculation indicates that a software system can be subjected to tens of thousands of different scenarios. Even if one were to execute just one test case against each scenario, obtaining any form of realistic coverage is infeasible for even the most resource-rich organisations. Cloud and grid infrastructures have been proposed as solutions to improving the scalability of software testing since 2008. However, we argue that cloud computing systems are too homogenous and are not representative of real-world usage scenarios. We refer to this problem as the Test Scenario Explosion Problem.peer-reviewe