Recommendations for Running a Tandem of Adsorption Chillers Connected in Series and Powered by Low-Temperature Heat from District Heating Network

In this paper, we investigate implications of running a cooling system of two silicagel/water adsorption chillers powered by a district heating network. The devices are connected in series, i.e., the heating water output from the primary chiller is directed to the secondary one. In consequence, the secondary device must deal with an even lower driving temperature and with temperature fluctuations caused by the primary device. We have evaluated three factors that influence the operation of those coupled devices: synchronization of their operating cycles, selection of their cycle time allocations (CTAs), and changing the heating water mass flow rate. Numerical analyses indicate that the performance of the secondary chiller drops significantly if the coupled devices that use the same CTA run asynchronously. The decrease is largest if the shift between the operating cycles is x=0.375 and x=0.875. We found that it is possible to reduce the negative influence of the asynchronous operation by implementing different CTA in each chiller. The best performance is achieved if the primary chiller uses an adsorption time to desorption time ratio f=1.0 and the secondary chiller uses f = 0.6–0.7.

Only Relative Speed Matters

Causal profiling is a novel and powerful profiling technique that quantifies the potential impact of optimizing a code segment on the program runtime. A key application of causal profiling is to analyze what-if scenarios which typically require a large number of experiments. Besides, the execution of a program highly depends on the underlying machine resources, e.g., CPU, network, storage, so profiling results on one device does not translate directly to another. This is a major bottleneck in our ability to perform scalable performance analysis and greatly limits cross-platform software development. In this paper, we address the above challenges by leveraging a unique property of causal profiling: only relative performance of different resources affects the result of causal profiling, not their absolute performance. We first analytically model and prove causal profiling, the missing piece in the seminal paper. Then, we assert the necessary condition to achieve virtual causal profiling on a secondary device. Building upon the theory, we design VCoz, a virtual causal profiler that enables profiling applications on target devices using measurements on the host device. We implement a prototype of VCoz by tuning multiple hardware components to preserve the relative execution speeds of code segments. Our experiments on benchmarks that stress different system resources demonstrate that VCoz can generate causal profiling reports of Nexus 6P (an ARM-based device) on a host MacBook (x86 architecture) with less than 16% variance.

Defect Texts Mining of Secondary Device in Smart Substation with GloVe and Attention-Based Bidirectional LSTM

In the process of the operation and maintenance of secondary devices in smart substation, a wealth of defect texts containing the state information of the equipment is generated. Aiming to overcome the low efficiency and low accuracy problems of artificial power text classification and mining, combined with the characteristics of power equipment defect texts, a defect texts mining method for a secondary device in a smart substation is proposed, which integrates global vectors for word representation (GloVe) method and attention-based bidirectional long short-term memory (BiLSTM-Attention) method in one model. First, the characteristics of the defect texts are analyzed and preprocessed to improve the quality of the defect texts. Then, defect texts are segmented into words, and the words are mapped to the high-dimensional feature space based on the global vectors for word representation (GloVe) model to form distributed word vectors. Finally, a text classification model based on BiLSTM-Attention was proposed to classify the defect texts of a secondary device. Precision, Recall and F1-score are selected as evaluation indicators, and compared with traditional machine learning and deep learning models. The analysis of a case study shows that the BiLSTM-Attention model has better performance and can achieve the intelligent, accurate and efficient classification of secondary device defect texts. It can assist the operation and maintenance personnel to make scientific maintenance decisions on a secondary device and improve the level of intelligent management of equipment.

Towards Secure and Usable Certificate-Based Authentication System Using a Secondary Device for an Industrial Internet of Things

As the number of controllers and devices increases in Industrial Internet of Things (IIoT) applications, it is essential to provide a secure and usable user authentication system for human operators who have to manage tens or hundreds of controllers and devices with his/her password. In this paper, we propose a formally verified certificate-based authentication system using a secondary network device for such IIoT applications. In the proposed system, a user’s sign key is encrypted with a secret key that can be computed with his/her password and a secret parameter in a secondary device to securely protect the sign key. To demonstrate the feasibility of the proposed system, we implemented a prototype with standard cryptographic algorithms (AES-256, RSA-3072, and ECDSA-256). The experiment results demonstrated that the execution time overhead of the sign key recovery process was 0.039 and 0.073 s, respectively, for RSA-3072 and ECDSA-256, which was marginal compared with the total execution time (0.383 s for RSA-3072 and 0.319 s for ECDSA-256) of the conventional system. We also verified the security of the proposed protocol using a formal verification tool called ProVerif.

Optimization of the Alignment Method for an Electric Vehicle Magnetic Field Wireless Power Transfer System Using a Low-Frequency Ferrite Rod Antenna

The establishment of international and regional standards for electric vehicle (EV) magnetic field wireless power transfer (MF-WPT) systems started in 2010 by the Society of Automotive Engineers (SAE). In the meantime, the EV MF-WPT standardization has been focused on primary device and secondary device topology. Recently, the International Organization for Standardization (ISO), the International Electrotechnical Commission (IEC), and SAE have begun describing the communication and alignment techniques for EV MF-WPT. In this paper, we present a fine positioning method using a low-frequency (LF) signal, as mentioned in IEC 61980 and SAE J2954. Through modeling and simulation, we optimized a LF ferrite rod antenna (FRA) for EV MF-WPT fine positioning. We also found the optimal arrangement of LF-FRAs on primary device and secondary device Finally, we used a test bench to experiment and check the results of our proposal.

Free Will, Determinism and Doing What You’re Told

This chapter discusses time travel as the secondary device for exploring the idea of liberty in Terry Gilliam's 12 Monkeys. It analyzes the juxtaposition between free will and determinism, in which the film seems to be caught in something of a bind. It also explains time travel that is one-directional, in which the scientists only ever send people into the past, never into their own future to see if their plan will pan out. The chapter talks about how 12 Monkeys seems to suggest that it is possible to influence the future, which is an idea that is entirely reliant on the illusion of linear time. It examines the debate between compatibilists and incompatibilists that centres on a failure to distinguish between that which is known and that which is real.