bluuebunny/crossref_metadata_2025 huggingface dataset:
Overheating Fault Analysis of Electromagnetic Unit in 220kv Capacitive Voltage Transformer
Authors: Xu Jianchun , Sui Wei , Song Yebin , Yang Xiaolei , Han Lu , Zhang Zhao , Tao Shuyi , Lin Yuan , Zhao Chuanzong , Zhang Hua , Wang Qinghao
Published: June 2020

This paper introduces the structure and principle of capacitive voltage transformer, the overheating caused by the failure of the electromagnetic unit on 220kV capacitive voltage transformer in operation is analyzed, it is based on infrared detection technology, combined with the method of power outage diagnostic test for joint fault diagnosis, the diagnostic results are accurate and reliable, some suggestions on field detection and fault diagnosis of capacitive voltage transformer are put forward.
Research on Optimal Design of Plug-in Hybrid Electric Vehicle Charging Based on Smart Grid
Authors: Wang Zhen , Chen Nuo , Guo Yanan
Published: June 2020

Plug-in hybrid vehicle charging piles are an important part of the smart grid, and electric vehicles are also an important means of alleviating energy shortages and environmental degradation. This article analyzes the influencing factors from three factors that determine the charging power. Finally, the charging power, charging demand and charging time are determined one by one to model the charging load of the electric vehicle. For the working frequency range of different equivalent resistances, wireless charging PID controller, battery charging state analysis, the equivalent resistances of different stages of the battery are studied, and the transmission efficiency of wireless charging technology is optimized, so that the transmitting mutual inductance coil is opposite to the receiving coil The offset is minimized to maximize the charging efficiency and simulations are performed. Simulation results from the final wireless charging technology of the car show that the wireless charging technology has a better effect.
A microgrid scheduling method based on Evolutionary Game
Authors: Xu Yue , Yan Xuefeng
Published: June 2020

In order to solve constrained scheduling problem in microgrid. A micrgrid scheduling method based on evolutionary game is proposed in this paper. Further more, a renewable energy and traditional energy generators group with different cost functions was studied as an example. The results show that evolutionary game method proposed in this paper has higher accuracy and stability than the existing artificial fish swarm optimization algorithm (AFS). In the scheduling model of microgrid, the optimized cost of power supply has been reduced by 2%.
Research on Pressure Stability Control of High-pressure Common Rail System Based on Differential Equation Optimization Model
Authors: Xu Jianping , Hu Hongming , Chang Wanfeng
Published: June 2020

To improve the accuracy of fuel injection in high-pressure common rail systems of diesel engine, a mathematical model based on differential equations was established in view of the process of fuel entering and ejecting the common rail pipe, and the pressure variation law under working condition in the common rail tube was simulated in this study. Aiming at reducing the fuel pressure fluctuations in the system, the optimal angular velocity of the cam in high-pressure pump is solved by binary search algorithm, and the optimal control strategies for maintaining the dynamic and stability of pressure are given as well. Numerical simulation results show that with the presented strategies precise control of the pressure can be achieved in the common rail system, helping to improve the efficiency of the diesel engines.
Analysis of the Generation and Weakening of Cogging Torque in Interior Permanent Magnet Machine
Authors: Sun Tao , Dai Ying , Wang ZiTeng , Liu WanQiu
Published: June 2020

The permanent magnet of interior permanent magnet motor is inside the rotor. Compared with the surface-mount permanent magnet motor, its equivalent air gap is small and the cogging torque has a great influence. In this paper, the cogging torque of interior permanent magnet synchronous motor is analyzed and deduced by the energy method. Taking the 48-slot/8-pole interior V-type permanent magnet synchronous motor as the research object, the influence of the axial segmented skew of the permanent magnets, the width of the stator slot and permanent magnets segmentation on the cogging torque was analyzed by the finite element method. Studies have shown that the reasonable selection of the above three methods can effectively weaken the cogging torque of V-type interior permanent magnet motor.
Design of Central Controller for EAST ECRH System Based on FPGA
Authors: Yong Yang
Published: June 2020

Electron cyclotron resonance heating is one of the important heating methods for controlled nuclear fusion reactions, which can make up for the shortcomings of the traditional heating methods. To this end, a 4MW long pulse electron cyclotron heating system was designed on the Experimental Advanced Superconducting Tokamak device. This paper mainly introduces the design of the gyrotron controller of ECRH system based on FPGA chip. The control logic of the central controller is based on state machine. Throughout the entire control process, each signal in the system is monitored in real time. Once an abnormality occurs, the main control logic will cut off the high voltage power of the gyrotron as required to protect the gyrotron from damage. In addition to the normal control logic, the FPGA also embeds abnormality diagnosis logic, which monitors the control state transitions of the main control logic and various input signals in real time to determine whether an abnormality has occurred in the system and can diagnose the cause of the abnormality. Timing simulation was done to the FPGA program. The result shows that the controller can respond to the total control trigger signal in real time, accurately control the switching of the cathode and anode high voltage power supply, diagnose and handle various abnormal conditions, and meet the control requirements of the ECRH system.
A bilinear robust state estimation method for electric thermal integrated energy system
Authors: Yang Xiaonan , Sun Bo , Han Feng , Lang Yansheng
Published: June 2020

A bilinear robust state estimation method for electric thermal integrated energy system (IEHS) is proposed. First, the linear weighted least absolute value (WLAV) model of IEHS is constructed by introducing auxiliary variables, and then the state variables are estimated by solving a quadratic programming model with a nonlinear transformation. The advantage of the proposed method is that it has a high calculation efficiency. The effectiveness of the proposed method is verified on the IEHS test system.
Design and output characteristic analysis for power head of truck-mounted drilling rig
Authors: Chang Jianghua , Zhang Yang , Tian Honglinag , Lu Feifei , Fan Dong , Zhou Zujie , Liu Qingxiu
Published: June 2020

Truck-mounted drilling rig is an important equipment for coalbed methane drilling construction, and the power head is one of the main actuators for truck-mounted drilling rig which has significant influence on technical feature of drilling rig. Now the power head of the rig is mostly driven by the motor + gear reduction unit to drive the main axle, the load change with the time, which had more influence on the rotation circuit. At the basis of analysis on load characteristics, a hydraulic control system with two-pump and two-circuit control was designed. The dynamic analysis model of the system is established, and the output characteristics of the system under no-load starting and on load starting are analysed. The analysis results show that: the response time of no-load starting pressure is 0.3s, the response time of on load starting pressure is 0.9s, the greater the load, the longer the response time; the output speed of the system reaches 120 r/min in the stable state.
Basic Event Probability Determination and Risk Assessment Based on Cause - Consequence Analysis Method
Authors: Xin Baoquan , Wan Lu , Yu Jianliang , Dang Wenyi
Published: June 2020

Reasonable determination of the probability of occurrence of basic events is the basis of scientific risk assessment. The cause-consequence analysis method developed from the theory of system reliability is an effective method to determine the probability of basic events. Taking the motor overheating event as an example, based on the reliability theory of human and machine, from the perspective of “safety control system for the occurrence and development of motor overheating fire event”, the “motor overheating safety control system” is determined as the target system. Through the investigation and analysis of the functional composition of the target system, the reliability block diagram of the target system is obtained. And the logical relationship of link events is determined. According to the reliability theory, the probability of each basic event is investigated and calculated. Finally, the risk assessment diagram of motor overheating is obtained. The results show that the equal risk line in logarithmic coordinate is a straight line. This line is the critical line of acceptable risk. This research solves the problems of the current cause effect analysis, such as the unclear choice of the target system, the confusion of the logical relationship between the link events and the unclear source of the basic data. The study of quantitative analysis details based on reliability theory improves the operability and application effect of cause consequence analysis method, which is helpful for its popularization and application.
Research on the Difference Significance of Test Score by SAS
Authors: Gao Huameng , Xue Yong , Sun Yu , Wang Jing
Published: June 2020

In order to research the significancy level and difference in different groups of test score data, the way for checking data’s normal character is introduced. In order to realizing variance analysis, t test and Wilcoxon test, the SAS function, such as SORT, UNIVARIATE NORMAL, TTEST COCHRAN and NPAR1WAY WILCOXON are presented. According to real data, the distribution histgraph, X2 values, normal test, signed-rank test, and Wilcoxon two-sample test are gained. The study in this paper can be adopted in other fields of test design and data analysis.
Coordinated Control Strategy Based on MMC and DFIG
Authors: Zhao Xiaomin , Yang Bingyuan
Published: June 2020

The AC-DC hybrid distribution network based on modular multilevel converters (MMC) is beneficial for receiving distributed generation (DG), energy storage devices and DC loads. Therefore, the coordinated control of MMC and DG is very important for its safe operation. In this paper, doubly-fed induction generator (DFIG) are used as DG, and the control strategies of DFIG and MMC systems are analyzed. The system modeling research is carried out on a real time digital simulator (RTDS) platform. Then based on MMC control, an improved adaptive Crowbar circuit is proposed to improve inverter AC system low-voltage ride-through (LVRT) capability. The results show that the coordinated control strategy can better compensate the reactive power of the system to achieve LVRT, and verify the effectiveness of the control strategy adopted by the converter station.
Design of Intelligent Partial Discharge Inspection System for Distribution Equipment Based on Internet of Things
Authors: Dai Jianzhuo , Jia Yongyong , Liu Yang , Yang Jinggang , Qin Jianhua , Yuan Dong , Liu Dandan
Published: June 2020

With the rapid development of information communication, the Internet of Things and other technologies, the distribution network has evolved from a single power network to intelligent information integration. Due to the characteristics of large-scale distribution network equipment, scattered deployment, and complicated operating environment, the operation and maintenance work has problems such as low working efficiency and severely insufficient measurement coverage. Based on this, this paper adopts the system architecture of cloud, pipe, edge, and end to design an intelligent inspection system for partial discharge of power distribution equipment. The system is mainly based on intelligent sensing and supplemented by mobile detection. It integrates advanced technologies such as intelligent sensing, big data analysis, wireless communication into all aspects of distribution network inspection, so as to realize intelligent sensing, data fusion analysis and fault alarms of distribution network, guide defect elimination work in time, and provides technical support for status maintenance and safe operation of distribution network equipment.
Temperature field simulation of medium and low voltage composite cable
Authors: Xiong Yiyong , Zhao Jinghong , Guo Guoqiang
Published: June 2020

This paper introduces the basic principle of calculating the temperature field of composite cable based on finite element method, and simulates the rated, short-circuit and overload conditions of the cable, and explains the situation of the temperature rise of the cable. The cable resistance is analyzed and calculated. In this paper, the temperature field of the composite cable is systematically studied by means of simulation, and the design conformity of the cable is verified.
Adaptive Proportional Complex Integral Control Strategy of Three-Phase Grid-connected PV Inverter
Authors: Teng Fuyao , Lou Yichuan , Chen Min
Published: June 2020

The performance of conventional controller of three-phase grid-connected inverters possibly deteriorate during grid frequency drift. In this paper, an frequency adaptive proportional complex integral (PCI) controller with frequency locking loop (FLL) was proposed, the FLL was utilized to adjust the resonant frequency of PCI automatically, and the zero current steady error was achieved by PCI controller. The validity of the proposed control scheme was demonstrated through results of simulation and experimental.
Interference analysis and suppression technology of converter transformer partial discharge test based on field measurement
Authors: Zhou Haibin , Wang Jingbao , Chen Wei
Published: June 2020

The field PD test of converter transformer is more difficult than that the test of common AC transformer. The most important difference is that the interference source in converter station is more complex. This paper measured the interference signals of the converter transformer field PD test in several converter stations, analyzed the characteristics of various typical interference, formulated the targeted interference suppression measures, simulation tests are carried out to verify the effectiveness of the suppression measures. Finally, the field application shows that the interference suppression measures proposed in this paper can effectively improve the efficiency and accuracy of field PD test of converter transformer.
Research on the Disadvantages and Countermeasures of Cross-subsidy for Sales Electricity Price
Authors: Zhang Jiaqi
Published: June 2020

In the context of deepening the reform of the power system and advancing the marketization of power, how to advance the price reform in an orderly manner has become an important issue in the reform process. Due to excessive consideration of economic structural adjustment and subsidies for agricultural residents’ electricity, the deviation between China’s sales price and electricity costs is very common, causing serious cross-subsidy problems. This paper applied Ramsey pricing theory, social welfare net loss theory, and cross subsidy application conditions to analyze the problems caused by cross subsidy of electricity price in China, and proposed several ideas and solutions to cross electricity subsidy.
Knowledge Transfer for Object Detection
Authors: Gong Chenggui , Zhang Xiao
Published: June 2020

Object detection is one of the basic tasks of computer vision. Although deep neural networks have greatly promoted the development of target detection, the training of deep neural networks often requires certain computing resources, especially when dealing with more complex detection tasks. It will become more complicated, and the increase in model complexity will increase its demand for computing resources. This is not desirable for platforms with limited computing resources. Without sacrificing excessive detection accuracy, how to make the model run efficiently on a platform with limited resources has become a big challenge. In order to solve this problem, we have introduced the idea of knowledge distillation in this work. We use the knowledge learned by complex models as prior knowledge, and pass the prior knowledge to the small-scale neural network model, so that the small-scale neural network model can acquire the similar functions of large-scale networks. Based on this, we proposed a framework for target detection based on knowledge distillation and conducted experiments on PASCAL VOC [1] and KITTI [2].

The experimental results show that the proposed framework can make the smaller student network show similar performance to the larger teacher network. This provides a possibility for the deep learning system to run efficiently on a resource-limited platform.
Research on Urban Distribution Network Planning and Optimization Measures Based on Real 3D Scenes
Authors: Fu Yaling , Li Chao , Qiu Kaifeng , Wang Yang , Zhang Chunhong
Published: June 2020

With the continuous advancement of smart grid construction, the structure of the power grid is becoming increasingly large and complex, and it is increasingly difficult to adapt to the requirements of grid development using traditional 3D drawings for grid design and operation and maintenance. The emerging 3D real-world modeling technology can visually and comprehensively display terrain, landforms, equipment appearance dimensions, wiring methods and other information. To promote the application of real-world 3D scene technology, electric power companies have repeatedly carried out 3D design of power grid projects and construction of data centers Optimized distribution network planning. Realize the linkage of real-world 3D scene plan maps, building information models, etc. through geographic connections, provide real feedback on site conditions, reduce the number of site surveys, save manpower and resources, and effectively implement urban power distribution network planning.
The Financial Analysis of Public Company in Stock Exchange Mergers Ratio
Authors: Gong Pei
Published: June 2020

The stock exchange mergers of public companies are the result of the modern market competition. Due to the advantages of the stock exchange mergers such as they are not limited by the scale of mergers, are able to prevent cash flow pressure, enjoy the policy of preferential tax and retain the owners’ equity, they are applied by more and more public companies. Based on CAPM (Capital Asset Price Model), the paper designs a model of the common stock in the capital market which integrates stock dividends into the process of bonus sharing. The stock exchange ratio of both companies who are going to merger is calculated by the equilibrium price through this model. It provides the preliminary reference for the operation of stock exchange mergers.
Selection of Input-Output Factors for Total Factor Productivity Evaluation of Chinese Power Grid Enterprises
Authors: Song Haiyun , Ma Li , Feng Xinxin , Xiao Hanxiong , Gao Guowei
Published: June 2020

In response to the call of the 19th CPC National Congress, China’s large-scale power grid companies have proposed in recent years to improve total factor productivity. Based on the analysis of the problems existing in the traditional efficiency evaluation methods of power grid enterprises and the importance of the evaluation of total factor productivity, combined with literature research, this paper focuses on the input-output factors with characteristics of power grid companies.
Research on Parallel Control Technology of Three-phase Inverter Based on Multiple Proportional Resonance Controller
Authors: Zhou Wei , Xu Xianglian , Tan Siyun , Mao Lukai , An Mengqiang , Luo Chenhu
Published: June 2020

The parallel operation of multiple inverters can increase the fault tolerance of the system and prevent the occurrence of major accidents. At the same time, it also has strong flexibility, which can reduce the volume and weight of the system and increase the capacity of the system, which is very attractive in the application of uninterruptible power supply. In the inverter parallel system, the circulation will be generated between the inverters due to the existence of the path. Circulation can cause current distortion, reduce system performance, and even damage equipment in severe cases. In order to effectively suppress the generation of circulation, this paper proposes a multiple proportional resonance control strategy for the parallel three-phase inverter system, that is, the voltage outer loop is controlled by PI+PR, and the current inner loop is controlled by PR. Two three-phase inverter parallel systems are built in MATLAB/Simulink simulation environment to compare and analyze the control effect of uncontrolled, traditional PI control and multiple PR control. The simulation results show that the proposed control method has a good suppression effect on the circulation generated in the inverter parallel system, even under the condition of unbalanced load.
Silicon Carbide devices for radiation detection and measurements
Authors: La Via F , Tudisco S , Altana C , Boscardin M , Ciampi C , Cirrone G A P , Fazzi A , Giove D , Gorini G , Lanzalone G , Muoio A , Pasquali G , Petringa G , Puglia S M R , Rebai M , Santangelo A , Trifirò A
Published: June 2020

In the last decades Silicon Carbide (SiC) received special attentions, in particular as semiconductor material, because is considered as alternative to Silicon for the future high-power, low consumption, radiation-hard microelectronics devices. This ambitious goal is particularly interesting also for the physics of the detectors. In this work are discussed some of the recent results obtained by SiCILIA collaboration, a joint research activity between INFN and IMM institutions to increase the level of technological development in the field of SiC detectors.
Investigation of convective heat transfer enhancement for nanofluid flow over flat plate
Authors: Klazly M M , Bognár G
Published: June 2020

In this paper, the laminar flow over flat plate of three different nanofluids is investigated. The fluid is considered as water with three different kind of solid particles Al2O3, TiO2, and Fe3O4 of different volume fractions (1, 2, 3, and 4%). The values of viscosity, heat capacity, density, and thermal conductivity depending on volume fraction for the three nanofluids are evaluated. Numerical simulation has been conducted for analysis the impact of the nanoparticles on the heat transfer properties, on the temperature and velocity profiles, on the wall shear stress and on the skin friction coefficient. The results show that as the value of volume fraction increases the values of the wall shear stress, skin friction, and heat transfer increase, but the velocity decreases. A comparison between the three nanofluids presents the difference in the thermal enhancement, velocity profiles, and thermal boundary layer. With the volume fraction for all three nanofluids polynomial connections has been obtained to describe for the relation of the wall shear stress, skin friction coefficient and average heat transfer coefficient.
CFD investigation of backward - facing step nanofluid flow
Authors: Klazly M M , Bognár G
Published: June 2020

Heat transfer enhancement of different nanofluid laminar flow over backward facing step is numerically studied in this paper. The expansion ratio is chosen according to the experimental setup suggested by Armaly H/h = 1.9432. The Reynolds number is taken in a range of 10 ≤ Re ≤ 400. The result showed a primary recirculation region developed after the sudden expansion before it starts to change to become fully developed flow downstream of the reattachment point. The length of the reattachment point increases as Reynolds number increases. The effect of the volume fraction has observed along the downstream wall for Al2O3 - water nanofluid. Moreover, the impact of the volume fraction on the thermal boundary layer and heat transfer is investigated.
Efficient checking of functional dependencies for relations
Authors: Sug Hyontai
Published: June 2020

Data consistency is very important in relational databases, because relational databases are adopted by most operational database and inconsistent data can generate inconsistent reports or search results. In order to avoid data inconsistency problem, the underlying relation variables should be at least in the third form. But, the relational variables may not be in the third normal form due to incorrect database design. In this paper an efficient method is suggested to prevent possible data inconsistency problem due to incorrect database design based on functional dependency checking on non-key attributes for stored data. The idea of the method is based on the principle of functional dependency on relational variables and sorting on non-key attribute values. An experiment was performed to show how we may detect possible functional dependencies in real database. A database called HR from Oracle is used for the experiment, where HR account has example relations designed by experts for practice. The experiment showed good results and found several possible functional dependencies between non-key attributes so that a database designer may use the found functional dependencies to improve the structure of the database.
On Bessel property of the system of root functions of the second order differential operator
Authors: Garayeva A T
Published: June 2020

In this paper studied the Bessel property of the system of root functions of a second order differential operator with summable coefficients. Established the criterion of Bessel property in L
2 (G), G = (0,1) of the system of root functions of the given operator.
On errors in Euler’s complex exponent and formula for solving ODEs
Authors: Manale Jacob M.
Published: June 2020

There are some mistakes in Euler’s works. Some of them form the basis of most of the sciences, including differential equations and complex analysis. We discuss them here.
Business and Economics: Metrics and Peer Review in the journal: “WSEAS Transactions on Business and Economics”
Authors: Bardis Nikos , Ekonomou Lambros , Borne Pierre , Ntalianis Klimis , Mercorelli Paolo , Katehakis Michael N , Kintzios Nikos , Bulucea Cornelia Aida , Planas Maria Isabella Garcia
Published: June 2020

The Conference MMCTSE 2020 was in collaboration with the Journal “WSEAS Transactions on Business and Economics”. In this paper, the Metrics, the Peer Review and some statistical results of this Journal: “WSEAS Transactions on Business and Economics” is outlined.
Some Scenarios on the impacts of the COVID-19 pandemic to automobile import demand function in Azerbaijan
Authors: Alikhanli Yegana
Published: June 2020

The article examines the possible scenarios of price changes in the car market of Azerbaijan as a result of Covid-19. In the study, the demand and supply functions were determined by the two-stage simultaneous equation method. The author concludes that the car market in Azerbaijan depends not only on domestic and world prices but also on household incomes. As Covid-19 pandemic reduces household incomes, as well as global incomes, it is likely that demand to import will be declined and domestic prices will be decreased. But by decreasing of supply amount the prices in the domestic market will not be declined strongly. As well as the demand function to import dependences on the world price.
Euclidean Jordan Algebras and Inequalities over the Spectrum of a Strongly Regular Graph
Authors: Vieira Luis
Published: June 2020

Let G be a primitive strongly regular graph of order n with three distinct eigenvalues and A its adjacency matrix. In this paper we associate to A the 3—dimensional real Euclidean Jordan algebra A spanned by In and the natural powers of A equipped with the Jordan product of matrices and with inner product of two matrices being the trace of their Jordan product and next, by the spectral analysis of some elements of A we establish some inequalities over the spectrum and the parameters of a strongly regular graph.
Dual Stage Network Intrusion Detection System Through Feature Reduction
Authors: Raj Raghuvansh , Gupta Somya , Lohia Manan , Taneja H C
Published: June 2020

With an exponential increase in the amount of data produced, transmitted, stored and exchanged over the internet, intrusion detection systems have formed an integral part of modern-day network security systems. Considerable expense, time and efforts are spent in ensuring timely detection and denial of malicious users in order to preserve the key objectives of system security; confidentiality, integrity, and availability. In this paper, we intend to propose a dual stage algorithm to tackle the problem of NIDS. Our aim in this paper is to construct an algorithm that results in few false positives and fewer false negatives, as any IDS should be.

Research into network intrusion detection systems dates back to the early 1990s where researchers initially developed rule-based algorithms such as SNORT and TCPDUMP. As the subject gained traction and importance, researchers began to shift efforts towards creating anomaly detection systems using benchmarked datasets to test their algorithms. In the early 2010s, several papers pertaining to NIDS were published, and a majority of the technological breakthroughs in this field were influenced by the theory of deep learning.

We have focused on building an IDS using the benchmarked NSL-KDD dataset. The dataset consists of 41 features, of which 3 are categorical and the remaining, numeric. Having opted for One-Hot Encoding of the categorical features, our feature space explodes to a sum of 122 features. Despite the obvious drawbacks, this was necessary as the categorical features do not contain any implicit ordering within their values. The aim is to develop an efficiently compressed feature space with the ultimate goal being to develop a computationally light classification model capable of operating on the compressed feature set using sequential models to our benefit.
First-order quantum phase transitions as condensations in the space of states
Authors: Ostilli Massimo , Presilla Carlo
Published: June 2020

We demonstrate that a large class of first-order quantum phase transitions, namely, transitions in which the ground state energy per particle is continuous but its first order derivative has a jump discontinuity, can be described as a condensation in the space of states. Given a system having Hamiltonian H = K + gV, where K and V are two non commuting operators acting on the space of states

F

, we may always write

F
=

F

cond

⊕

F

norm

where

F

cond

is the subspace spanned by the eigenstates of V with minimal eigenvalue and

F

norm

=

F

cond

⊥

. If, in the thermodynamic limit, M
cond/M → 0, where M and M
cond are, respectively, the dimensions of

F

and

F

cond

, the above decomposition of

F

becomes effective, in the sense that the ground state energy per particle of the system, ϵ, coincides with the smaller between ϵ
cond and ϵ
norm, the ground state energies per particle of the system restricted to the subspaces

F

cond

and

F

norm

, respectively: ϵ = min{ϵ
cond, ϵ
norm}. It may then happen that, as a function of the parameter g, the energies ϵ
cond and ϵ
norm cross at g = g
c. In this case, a first-order quantum phase transition takes place between a condensed phase (system restricted to the small subspace

F

cond

) and a normal phase (system spread over the large subspace

F

norm

). Since, in the thermodynamic limit, M
cond/M → 0, the confinement into

F

cond

is actually a condensation in which the system falls into a ground state orthogonal to that of the normal phase, something reminiscent of Anderson’s orthogonality catastrophe (Anderson 1967 Phys. Rev. Lett.
18 1049). The outlined mechanism is tested on a variety of benchmark lattice models, including spin systems, free fermions with non uniform fields, interacting fermions and interacting hard-core bosons.
Guidelines for Climate Change Adaptation in Brazilian Cities Through Urban Green Infrastructure
Authors: Almeida J , Engel C
Published: June 2020

One of the significant challenges for managers and urban planners today is adapting cities to climate change. Studies published in the Assessment Reports (AR) of the Intergovernmental Panel on Climate Change (IPCC) indicated several evidences of climate change and also showed possible impacts on urban infrastructure, service availability and natural resources. Thus, adaptation actions emerge as a necessary coping strategy and search for urban resilience. Green infrastructure refers to a set of interventions aimed to preserve natural ecosystems and to support for urban systems. This research aims to identify what are the main impacts projected for the Brazilians cities, due to climate change, and also provide guidelines to the green infrastructure adoption as an adaptation strategy. The methodology was based on the evaluation of the general panorama of climate change on the national context indicated by the Brazilian Panel on Climate Change (PBMC). In addition, a review of articles related to green infrastructure was made aiming for the selection of possible solutions focused on its applicability. As a result, guidelines for urban planning were settled as a contribution to reducing the vulnerability of Brazilians cities.
Thermal design and on-orbit performance of the ECOSTRESS instrument
Authors: Cha J , Carroll B , Rodriguez J , Maynard K , Romero M
Published: June 2020

The ECOSystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) instrument, launched on June 29, 2018, has completed nine months of operation in space. ECOSTRESS is a multi-spectral thermal infrared imaging radiometer and its primary mission is to investigate and understand how climate change affects water and carbon usage on Earth. The thermal control subsystem consists of a combination of active and passive components to maintain instrument components within the allowable flight temperature limits. Its focal plane detector is cooled to 65K by a pair of mechanical cryocoolers and a third mechanical cryocooler cools an intermediate cold shield to 130K. The heat dissipation generated by cryocoolers and electronics, is removed through non-planar cold plates and tube-on plate heat exchanger, which are cooled by a circulating fluid loop inside JAXA’s JEM-EF module. The heat collected by the JEM-EF fluid is exchanged with a fluid loop that circulates through radiators located on the exterior of the Space Station. This paper provides an overview of the thermal and cryogenic system design, thermal analysis results and reviews the on-orbit thermal performance.
Propellant liquefaction modelling compared against liquefaction testing
Authors: Kashani A , Hauser D , Desai P
Published: June 2020

Current proposed NASA missions to Moon and Mars involve producing cryogenic propellant in-situ to reduce launch mass and requirements. One technique for liquefaction of the gases produced through electrochemical processes is to circulate cold gaseous neon or helium through broad area cooling tubes attached to the outside of the propellant tanks. To determine the performance of this liquefaction process tests are being conducted at NASA Marshall Space Flight Center in a 4.25 cubic meter tank with a broad area cooling network. A transient computational fluid dynamic code coupled with a thermal model of the tank and its cooling loops is developed in Thermal Desktop to compare against the results of these tests. Details of the model and the model predictions and comparison to experimental data from recent liquefaction tests are presented here.
Thermal and exported vibration characterization of RICOR K508N cryocooler
Authors: Mok M A , McKinley I M , Mastropietro A J
Published: June 2020

The RICOR K508N is an upgraded version of the K508 that has extensive flight heritage. This paper reports on the thermal performance and exported force results for a COTS K508N for the ATACOI project as well as two K508N coolers filled to a higher fill pressure and with a high frequency motor for the CIRAS mission. The thermal performance of the coolers was measured in vacuum for -40°C, 20°C and 57°C heat reject temperatures. The coolers were operated in open-loop and in closed-loop mode during thermal performance testing. The K508N for ATACOI was put through Protoflight/Qualification thermal vacuum testing in order to satisfy JPL environment requirements for flight. Exported vibration results for the ATACOI, CIRAS and MASPEX coolers are presented and compared. Finally, the ATACOI K508N was tested with and without wire rope vibration isolators to validate the results presented in Ref. [11]. As a result of increased fill pressure and a high frequency motor, the CIRAS coolers showed a 22% performance improvement at 90 K compared to the ATACOI cooler.
Fluid mechanical response of a pulse tube cryocooler: modelling and experimental validation
Authors: Lauzier K , Bribiesca-Argomedo F , Gauthier J-Y , Sesmat S , Lin-Shi X , Carvalho Lopes D
Published: June 2020

Earth observation satellites require cryocoolers to cool down their infrared imagers at very low temperatures. Besides having very good thermodynamic performances, satellite cryocoolers are expected to generate as little vibrations as possible. In order to better understand vibration causes between 50 and 500 Hz, a precise model of the whole cryocooler is necessary. In the literature, two main modelling approaches for pulse tube cryocoolers exist: compressororiented models reduce the thermodynamic system to a linear mass-spring-damper system acting on compressor’s pistons; and thermodynamically oriented models aimed at understanding and predicting thermodynamic performances.

In this paper, the mechanical behavior of the thermodynamic system is modelled. Assumptions concerning gas properties and thermodynamic behavior are made based on SAGE software simulations. A simplified Redlich Kwong equation is used. When necessary, polytropic coefficients were identified using simulation data, as were the time-averaged temperatures. The thermodynamic system is split into volumes, pipes and regenerators: conservation laws in volumes are integrated, dynamic mass and momentum conservation equations in pipes are solved using the method of characteristics and equations in regenerators are solved using a finite difference method. Three friction laws are used: one for straight pipes (Moody chart), another for wound pipes (White’s correlation) and a last one for porous media (Modified Ergun equation). Porosity is measured by weighing. The model is built to respect integral causality and propagation phenomena.

The developed model is validated using experimental data. The simulations highlight the non-linear mechanical behavior of the thermodynamic system: a sinusoidal motion of the pistons induces a non-sinusoidal pressure in the compression chamber. Among other, first and second harmonics amplitudes are about 3% of fundamental pressure amplitude.

This model can now be integrated into a global cryocooler model to predict compressor’s vibrations, power consumption or electrical harmonics. It could also be extended to predict vibrations from the thermodynamic system.
Sensitivity analysis on miniaturize pulse tube boundary layer losses
Authors: Ghavami Ali , Kirkconnell Carl , Mostafa Ghiaasiaan S
Published: June 2020

Miniaturized cryocooler systems are among the key components of state-of-art infrared sensing small satellites (SmallSats). To achieve small size, these cryocoolers need to operate at high frequencies, e.g., 200 to 300 Hz range. High frequency leads to lower compression and expansion swept volumes and hence a smaller cryocooler. Previously we showed that pulse tube cryocoolers have high boundary layer losses for small size pulse tube diameters, which results in low thermodynamic efficiency. In this follow-up study we present a sensitivity analysis on the pulse tube boundary layer losses and investigate the effects of the bounding temperatures, pulse tube aspect ratio, operating frequency and pulse tube diameter. Computational fluid dynamics (CFD) is used for this sensitivity analysis. The results allow us to find the threshold conditions beyond which a miniature pulse tube cryocooler can no longer be effective for use at high frequencies.
80 K vibration-free cooler for potential future Earth observation missions
Authors: Barreto J. , Martins D. , Branco M.B.C. , Ribeiro R.P.P.L. , Esteves I.A.A.C. , Mota J.P.B. , Branco J.B. , Gonçalves A.P. , Tirolien T. , Bonfait G.
Published: June 2020

A solution for a “vibration-free” Joule-Thomson cooler using a sorption compressor is presented to answer the needs of potential future Earth observation IR missions with low micro-vibration levels requirements from the European Space Agency. The adopted solution includes a closed cycle JT cooler, using nitrogen as working fluid with an expected cooling power of 1.5W@80K and the fluid circulation is achieved by cycles of adsorption/desorption using metal organic framework sorbent materials.

The working principle and chosen parameters of the 80 K vibration-free cooler are shown based on the various stringent requirements (temperature range, performance, consumption etc.) The characterization and validation of some components was already carried out: preliminary results are presented.
Experimental validation and refinement of mixture optimization for a mixed gas Joule-Thomson cycle
Authors: Detlor J , Gruenstern R , Pfotenhauer J , Nellis G
Published: June 2020

An initial prototype of a mixed gas Joule-Thomson (JT) cryocooler was constructed and installed in a test facility to experimentally validate and refine a computational tool developed to optimize the gas mixture composition for a Joule-Thomson cycle with specific operating parameters. The mixture optimization model determines an optimal three-component mixture based on the analysis of the maximum value of the minimum isothermal enthalpy change, ΔhT
, that occurs over the operating temperature range coupled with an evaluation of the percent of the heat exchanger that exists in a two-phase state within that range. The heat exchanger performance model has been refined and expanded to determine both the steady-state and transient operation of the system. The initial prototype of the JT cryocooler was installed in a test facility capable of providing and measuring a range of gas composition, molar flow rates, and pressures. The JT cryocooler has been operated while charged with several gas mixtures over a range of operating pressures. The pressure drop and temperature at the outlet of the JT valve were compared to the expected values based on the mixture optimization model. Results were used to refine the model, particularly the heat exchanger performance model, and gain confidence in its ability to steer future experimental iterations. A second prototype of decreased size with increased heat exchanger conductance, minimized parasitic heat loss and improved instrumentation is being developed to further investigate optimal mixture selection, particularly in the 120-150K cold head temperature range.
Thermodynamic comparison of small liquid nitrogen generators driven by mixed-refrigerant J-T refrigerators and gas expansion cycles
Authors: Wang H C , Guo H , Chen G F , Song Q L , Gong M Q
Published: June 2020

The thermodynamic comparison of small mixed-refrigerant J-T (MRJT) and gas expansion (Kapitza cycle) LN2 generators are conducted by the exergy method in this paper. Both of two types are employed for low pressure N2 liquefaction and air separation (< 9.0 bar). Pure N2, PSA units or cryogenic air separation columns are used for LN2 production. The MRJT type is driven by single-stage compressors. It is indicated that the efficiency of MRJT type is higher than Kapitza type. With pure N2 at 8.0 bar, the figures of merit (FOM) of MRJT and Kapitza types are 26.86% and 12.79%, respectively. With mini air separation columns, the FOM of MRJT and Kapitza types are 21.42% and 11.34%, respectively. The large exergy losses in the compressor unit and non-isentropic expansion are the main reasons of the inferior efficiency of the Kapitza type. In addition, the Kapitza type requires larger total compressor displacement than the MRJT type. The MRJT type is recommended to be used in small LN2 generators.
Design of the DUNE APATF cryogenic system
Authors: Dalesandro A , Voirin E , Montanari D , Tope T
Published: June 2020

Fermi National Accelerator Laboratory (FNAL) is developing the international Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) to advance neutrino science. The flagship of the DUNE project consists of a large particle detector constructed one-mile (1.6 km) beneath the surface at the Sanford Underground Research Facility (SURF) in Lead, SD. The SURF detector is the largest of its type ever built and is comprised of four cryostats totaling 70,000 tons of liquid argon (LAr) to record neutrino interactions with unprecedented precision. Each cryostat houses a detector, the first includes 150 Anode Panel Assemblies (APA) submersed within 17,500 tons of LAr. Before installing 150 APA within the SURF detector they will be cryogenically cooled to nominally 90 K at the APA Test Facility (APATF) utilizing nitrogen flows. The APATF cryogenic system is entirely located one-mile underground at the SURF facility and includes nominally 13 kW of refrigeration at 80 K, cryogenic transfer lines, APA test cryostats, a cryogenic control system, and various control and pressure safety elements to ensure performance and safety requirements are achieved. The APATF preliminary design is in progress and major considerations include an efficient, cost-effective mechanism to deliver the required refrigeration to the APATF underground, support of rigid testing intervals to support the DUNE operating schedule, temperature stability of the APA and electronics within cryostats, efficient cryogenic system operation to minimize heat leak and/or liquid nitrogen consumption, thermo-mechanical stability and flexibility of components, and pressure safety of the APATF cryogenic system. Installation and integration of the APATF cryogenic system within the footprint and to adjacent sub-systems is also discussed.
Progress towards Operation of a Deuterium Cold Neutron Source at the NCNR
Authors: Jurns J , Middleton M , Williams R
Published: June 2020

The NIST Center for Neutron Research (NCNR) operates a 20 MW research reactor that produces neutrons for a suite of 30 neutron scattering instruments. 70% of these instruments use cold neutrons (E<5 meV), which are moderated by two separate cold neutron sources. The cold moderator for both sources is liquid hydrogen (LH2), which is in turn cooled by a recently commissioned 7 kW, 14K helium refrigerator. NCNR plans to replace the larger cold source with a new one operating with liquid deuterium (LD2). This report focuses on progress towards the upgrade to liquid deuterium, and options to address the particular challenges of designing and operating a cooling system that simultaneously supports operation with both LH2 and LD2.
Cryogenic Performance Test Platform for the Gas Bearings of Helium Turbine Expanders
Authors: Li S S , Fu B , Zhang Q Y , Zhu P , Lu X F , Ma D K , Yuan K
Published: June 2020

The turbo-expander is the core part of the helium refrigerator, and the gas bearing is the critical component influences the stability of the machine. There is 300 K operating temperature difference between the turbine wheel and the gas bearing regions in the helium turbo-expander. Therefore, it is necessary to consider the heat transfer between the bearing surfaces, nominally at room temperature, and the rest of the machine when studying bearing dynamic stability. This paper describes a cryogenic test platform that is being developed to analyze the dynamic performance of gas bearings with cryogenic gas supply. The system flow loop has been designed for bearing and small turbine testing at 80 K and above. The experimental method has been determined. All of the components are ready for the cold box assembly. The commissioning of the platform will be carried out in the near future.