The co-movement of asset returns and the micro-macro focus of prudential oversight

The integration of micro-prudential oversight with the macro-approach to financial stability -- long in the making -- raises several issues of coordination of regulatory responsibilities. This paper argues that a decomposition of the covariance of asset returns into an endogenous volatility component -- which can be reduced -- and an exogenous volatility component -- which we have to live with -- helps address these coordination issues and provides the basis for financial health diagnostics and supervisory responses to observed symptoms of financial instability. By linking risk origination and risk control, the paper may also contribute to the search for an operational definition of the term"macro-prudential."Mutual Funds,Debt Markets,Markets and Market Access,Emerging Markets,Labor Policies

Research program on holographic instrumentation Final report

Holographic instrumentation for particle impact studies and interferometer system

Updates to Multi-Dimensional Flux Reconstruction for Hypersonic Simulations on Tetrahedral Grids

The quality of simulated hypersonic stagnation region heating with tetrahedral meshes is investigated by using an updated three-dimensional, upwind reconstruction algorithm for the inviscid flux vector. An earlier implementation of this algorithm provided improved symmetry characteristics on tetrahedral grids compared to conventional reconstruction methods. The original formulation however displayed quantitative differences in heating and shear that were as large as 25% compared to a benchmark, structured-grid solution. The primary cause of this discrepancy is found to be an inherent inconsistency in the formulation of the flux limiter. The inconsistency is removed by employing a Green-Gauss formulation of primitive gradients at nodes to replace the previous Gram-Schmidt algorithm. Current results are now in good agreement with benchmark solutions for two challenge problems: (1) hypersonic flow over a three-dimensional cylindrical section with special attention to the uniformity of the solution in the spanwise direction and (2) hypersonic flow over a three-dimensional sphere. The tetrahedral cells used in the simulation are derived from a structured grid where cell faces are bisected across the diagonal resulting in a consistent pattern of diagonals running in a biased direction across the otherwise symmetric domain. This grid is known to accentuate problems in both shock capturing and stagnation region heating encountered with conventional, quasi-one-dimensional inviscid flux reconstruction algorithms. Therefore the test problems provide a sensitive indicator for algorithmic effects on heating. Additional simulations on a sharp, double cone and the shuttle orbiter are then presented to demonstrate the capabilities of the new algorithm on more geometrically complex flows with tetrahedral grids. These results provide the first indication that pure tetrahedral elements utilizing the updated, three-dimensional, upwind reconstruction algorithm may be used for the simulation of heating and shear in hypersonic flows in upwind, finite volume formulations

Viking '75 spacecraft design and test summary. Volume 3: Engineering test summary

The engineering test program for the lander and the orbiter are presented. The engineering program was developed to achieve confidence that the design was adequate to survive the expected mission environments and to accomplish the mission objective

MoMA Algorithm: A Bottom-Up Modeling Procedure for a Modular System under Environmental Conditions

The functioning of complex systems relies on subsystems (modules) that in turn are composed of multiple units. In this paper, we focus on modular systems that might fail due to wear on their units or environmental conditions (shocks). The lifetimes of the units follow a phase-type distribution, while shocks follow a Markovian Arrival Process. The use of Matrix-Analytic methods and a bottom-up approach for constructing the system generator is proposed. The use of modular structures, as well as its implementation by the Modular Matrix-Analytic (MoMA) algorithm, make our methodology flexible in adapting to physical changes in the system, e.g., incorporation of new modules into the current model. After the model for the system is built, the modules are seen as a ‘black box’, i.e., only the contribution of the module as a whole to system performance is considered. However, if required, our method is able to keep track of the events within the module, making it possible to identify the state of individual units. Compact expressions for different reliability measures are obtained with the proposed description, optimal maintenance strategies based on critical operative states are suggested, and a numerical application based on a k-out-of-n structure is developed.Spanish Ministry of Science and Innovation-State Research Agency PID2020-120217RB-I00 PID2021-123737NB-I00Junta de Andalucia B-FQM-284-UGR20 CEX2020-001105-/AEI/10.13039/50110001103

Instrumentation design study for testing a hypersonic ramjet engine on the x-15 a-2. volume 3- conceptual design of measurement systems

Instrumentation for testing hypersonic ramjet engine on X-15A-2 aircraf

MEMS Oscillator를 탑재한 우주발사체용 위성항법수신기 성능 향상

학위논문(박사) -- 서울대학교대학원 : 공과대학 기계항공공학부, 2021.8. 박찬국.In this dissertation, the environmental and performance results of TCXO (temperature controlled crystal oscillator) and MEMS (micro electro mechanical system) oscillator are presented. The test results for each oscillator are compared, and based on the test results for the GNSS receiver to which each oscillator is applied, the replaceability of TCXO with MEMS oscillator is discussed. TCXO is a component that supplies a fixed and stable reference frequency by using a quartz crystal with a piezo electric effect, and it has low phase noise, high Q factor fitted for a resonator. The TCXO is widely used in precise clock and timing equipment as well as GNSS receivers. Through many temperature tests during development, the high level of frequency stability over temperature can be achieved by the surrounding compensation circuit. MEMS oscillator drastically reduced its size and weight by introducing micro scale manufacturing and packaging technology and uses silicon as a resonator. This reduction in size and weight makes MEMS oscillator robust under physical stress such as vibration and shock. However, silicon, which is used as a resonator of MEMS oscillator, has lower frequency stability over temperature compared to a quartz crystal, and relatively high phase noise occurs as the complex compensation circuit is required. Despite its advantages, the MEMS oscillator has not been widely used so far due to the tendency to use existing TCXOs. Electronic devices in space launch vehicles experience significant vibration, acceleration, and shock at the flight events such as lift-off, engine shutdown, stage, and pairing separation. And the performance tests under these physical stresses to verify operability should be conducted. In the pyrotechnic shock test, the GNSS receiver equipped with TCXO as a reference oscillator cannot maintain signal tracking, making the position fix fail. This phenomenon was caused by a sudden change in frequency output of TCXO due to the shock, and to address this issue, a MEMS oscillator, which is known to be robust in harsh environmental and stress conditions, was chosen to be utilized as a reference frequency oscillator instead of TCXO. To use the MEMS oscillator as a reference frequency of a GNSS receiver, the pyrotechnic shock, vibration, and temperature test for the MEMS oscillator itself were performed before assemble the GNSS receiver. In order to check the behavior of the GNSS receiver under the reference frequency change, the test using a signal generator, which simulates the reference frequency change without physical shock, was performed. After the test for the MEMS oscillator itself, the test of the GNSS receiver with the MEMS oscillator was conducted. The GNSS receiver can maintain signal tracking and calculate position normally under the pyrotechnic shock test, and the vibration and temperature tests are done without any issues. In environmental and performance tests, there are no problems due to the high phase noise of the MEMS oscillator, and the navigation accuracy was not much different from the existing GNSS receiver with TCXO.본 학위논문에서는 온도보상 수정발진기와 멤스 발진기에 대한 환경시험 및 성능시험 결과를 제시한다. 또한 각각을 탑재한 위성항법수신기에 대한 검증시험을 통해 위성항법수신기에 널리 사용되고 있는 온도보상 수정발진기를 물리적인 충격에 강인한 멤스 발진기로 대체하고자 한다. 온도보상 수정발진기는 압전성질을 지닌 쿼츠를 이용하여 안정적이고 정확한 주파수를 출력하는 부품으로 위상잡음과 손 실이 작아 기준주파수로 적합하다. 온도보상 수정발진기는 이미 정밀시계와 시각장치에 많이 이용되고 있으며, 위성항법수신기에도 널리 사용되고 있다. 단순한 수정진동자는 주변 온도에 민감하게 반응하지만 온도보상 수정발진기는 주변 온도를 측정하는 보상회로가 삽입되어 높은 온도 안정성을 보인다. 멤스발진기는 멤스 기술과 반도체 생산 기술에서 파생된 제조 기술을 바탕으로 온도보상 수정발진기와 비교해서 크기와 무게를 크게 줄였다. 크기가 작아짐에 따라 물리적인 충격과 진동에 강하나 출시 초기에는 높은 위상잡음과 온도변화에 의해 주파수 안정성이 낮아 제한적인 용도에만 사용되어 왔다. 최근 반도체 제작기술의 발달로 멤스 발진기도 온도보상 수정발진기 수준의 잡음 성능을 보이며, 시스템과의 일체화가 더욱 쉬워 응용분야가 넓어지고 있다. 우주발사체의 전자탑재물은 엔진 점화 혹은 페어링 분리와 같은 이벤트가 있을 때마다 강한 진동, 가속도 및 충격을 겪는다. 따라서 전자탑재물 제작시 온도, 진동, 가속도 및 충격과 같은 환경시험 을 수행하는데 온도보상 수정발진기를 탑재한 위성항법수신기가 파이로 충격시험시 항법신호를 놓치는 놓치는 문제가 발생하였다. 이 현상은 위성항법수신기에 탑재된 온도보상 수정발진기의 출력주파수가 충격에 의해 급격히 변하였기 때문이며 이를 위해서 여러 종류의 온도보상 수정발진기를 시험해보았으나 해결이 어려웠다. 멤스 발진기의 위성항법수신기 적용가능성을 확인하기 위해 먼저 파이로 충격환경 하에서 기존 수신기 추적루프에 대한 분석을 제시한다. 그리고 멤스 발진기에 대해 기존에 수행했던 온도, 진동 및 파이로 충격시험을 수행하고 온도보상 수정발진기와 주파수 출력을 비교하였다. 물리적인 환경인 진동과 파이로 충격 이외에 온도에 대해서도 멤스 발진기는 온도보상 수정발진기에 비해 좋은 주파수 안정성을 보였다. 멤스 발진기 자체의 환경시험 이후 위성항법수신기에 탑재하여 동일한 환경에서의 동작 성능을 확인하였고, 온도보상 수정발진기가 탑재된 기존의 위성항법수신기와 비교하여 성능차이가 없었으며 파이로 충격시험에서는 항법신호를 놓치지 않고 연속적인 항법을 수행하였다. 앞서 수행된 시험을 바탕으로 멤스 발진기를 위성항법수신기에 탑재하는데는 문제가 없음이 확인되어 온도보상 수정발진기를 대체할 수 있을 것으로 판단된다.Chapter 1 Introduction . 1 1.1 Motivation and Background 1 1.2 Objectives and Contributions . 4 1.3 Organization of the Dissertation . 5 Chapter 2 Oscillators for Timing Source 6 2.1 Barkhausen Criterion 7 2.2 TCXO . 9 2.2.1 TCXO Fundamentals . 10 2.2.2 TCXO Oscillator model 14 2.2.3 Pierce Oscillator Design Example . 19 2.2.4 TCXO in GNSS receivers . 23 2.3 MEMS Oscillator . 29 2.3.1 Electrostatic MEMS Oscillator model 33 Chapter 3 Environmental Test Results of Oscillators . 41 3.1 Oscillator Behavior under Environmental Stress . 43 3.1.1 Vibration and Acceleration Sensitivity 44 3.1.2 Temperature Sensitivity . 49 3.1.3 Pyrotechnic Shock . 56 3.2 Frequency Stability during the Temperature Test . 60 3.3 Frequency Stability during the Vibration Test 64 3.4 Frequency Stability in Pyrotechnic Shock Test 70 Chapter 4 Simulation with GNSS Receiver under Reference Frequency Change . 74 4.1 Tracking Loop of GNSS Receiver 75 4.2 GNSS Receiver Operation under the Change of Reference Frequency 86 4.3 False Frequency Lock 96 Chapter 5 Environmental Test Results of GNSS Receiver . 103 5.1 Navigation Performance during the Temperature Test . 105 5.2 Navigation Performance during the Vibration Test 108 5.3 Navigation Performance during the Pyrotechnic Shock Test 111 Chapter 6 Conclusion 115 Bibliography 117박

Pulsed electromagnetic gas acceleration Semiannual progress report, 1 Jul. - 31 Dec. 1968

Pulsed electromagnetic gas acceleratio

Structural dynamics branch research and accomplishments to FY 1992

This publication contains a collection of fiscal year 1992 research highlights from the Structural Dynamics Branch at NASA LeRC. Highlights from the branch's major work areas--Aeroelasticity, Vibration Control, Dynamic Systems, and Computational Structural Methods are included in the report as well as a listing of the fiscal year 1992 branch publications

Presolar Grains from Novae: Evidence from Neon and Helium Isotopes in Comet Dust Collections

Presolar grains in meteorites and interplanetary dust particles (IDPs) carry non-solar isotopic signatures pointing to origins in supernovae, giant stars, and possibly other stellar sources. There have been suggestions that some of these grains condensed in the ejecta of classical nova outbursts, but the evidence is ambiguous. We report neon and helium compositions in particles captured on stratospheric collectors flown to sample materials from comets 26P/Grigg-Skjellerup and 55P/Tempel-Tuttle that point to condensation of their gas carriers in the ejecta of a neon (ONe) nova. The absence of detectable 3He in these particles indicates space exposure to solar wind (SW) irradiation of a few decades at most, consistent with origins in cometary dust streams. Measured 4He/20Ne, 20Ne/22Ne, 21Ne/22Ne and 20Ne/21Ne isotope ratios, and a low upper limit on 3He/4He, are in accord with calculations of nucleosynthesis in neon nova outbursts. Of these, the uniquely low 4He/20Ne and high 20Ne/22Ne ratios are the most diagnostic, reflecting the large predicted 20Ne abundances in the ejecta of such novae. The correspondence of measured Ne and He compositions in cometary matter with theoretical predictions is evidence for the presence of presolar grains from novae in the early solar system.Comment: As appeared in the Astrophysical Journa