Political identity and financial risk taking: Insights from social dominance orientation

This article investigates how people’s political identity is associated with their financial risk taking. The authors argue that conservatives’ financial risk taking increases as their self-efficacy increases because of their greater social dominance orientation, whereas liberals’ financial risk taking is invariant to their self-efficacy. This central hypothesis is verified in six studies using different measures of political identity, self-efficacy, and financial risk taking. The studies also use different samples of U.S. consumers, including online panels, a large-scale data set spanning five election cycles, and a secondary data set of political donations made by managers at companies. Finally, the authors articulate and demonstrate the mediating effect of individuals’ focus on the upside potential of a decision among conservatives but not liberals

Quantitative agreement of Dzyaloshinskii-Moriya interactions for domain-wall motion and spin-wave propagation

The magnetic exchange interaction is the one of the key factors governing the basic characteristics of magnetic systems. Unlike the symmetric nature of the Heisenberg exchange interaction, the interfacial Dzyaloshinskii-Moriya interaction (DMI) generates an antisymmetric exchange interaction which offers challenging opportunities in spintronics with intriguing antisymmetric phenomena. The role of the DMI, however, is still being debated, largely because distinct strengths of DMI have been measured for different magnetic objects, particularly chiral magnetic domain walls (DWs) and non-reciprocal spin waves (SWs). In this paper, we show that, after careful data analysis, both the DWs and SWs experience the same strength of DMI. This was confirmed by spin-torque efficiency measurement for the DWs, and Brillouin light scattering measurement for the SWs. This observation, therefore, indicates the unique role of the DMI on the magnetic DW and SW dynamics and also guarantees the compatibility of several DMI-measurement schemes recently proposed.Comment: 24 pages, 5 figure

중금속/강자성 다층박막에서 비대칭 교환상호작용에 대한 연구

스핀파 (spin wave), 쟐로신스키-모리야 상호작용 (Dzyaloshinskii-Moriya interaction), 수직 자기이방성 (perpendicular magnetic anisotropy), 브릴루앙 광 산란 분광계 (Bril-louin light scattering spectroscopy), 자기광학 커 효과 (magneto-optical Kerr effect)Recently, the interfacial Dzyaloshinskii-Moriya interaction has been intensively investigated in the spotlight. This phenomenon is significantly considered due to potential application as it could open new paths to manipulate a quasiparticle information based on skyrmion. From several reports, the magnetic skyrmion state is well-known depending on Dzyaloshinskii-Moriya interaction energy density. To investigate this fun-damental asymmetric exchange interaction, the exact and reliable method in the quantitative determination of the interfacial Dzyaloshinskii-Moriya interaction energy density is highly required. Therefore, we study the magnetic thin film structure of the heavy metal (HM)/ferromagnet (FM) multilayers involving the perpendic-ular magnetic anisotropy obtained from the strong spin-orbit coupling of the heavy metal layer in this Thesis. Especially, we focus on the interfacial Dzyaloshinskii-Moriya interaction energy density and the perpendicu-lar magnetic anisotropy. For the measurements, the Brillouin light scattering spectroscopy, hence, is mainly used. This measure-ment system is a well-known multi-purpose tool to investigate the thermally excited propagating spin wave to obtain the fundamental magnetic properties such as the perpendicular magnetic anisotropy, the saturation magnetization, the exchange stiffness constant, and the magnetic damping simultaneously. Furthermore, it can be directly determined the Dzyaloshinskii-Moriya interaction derived from the spin wave frequency dif-ferences of propagating spin waves in the spectrum of Brillouin light scattering spectroscopy. The main results are composed in the two parts such as the HM1/ferromagnet/ HM2 heterostructures depending on the stack-ing order of the HM, and the investigating method with anti-reflection layer for an accurate determination of interfacial Dzyalshinskii-Moriya interaction energy density in the HM/FM multilayers. These results are shown the potentiality for the finding of a stable skyrmion state and the more precise interfacial Dzyaloshinskii-Moriya interaction energy density by an using anti-reflection layer.| 쟐로신스키-모리야 (Dzyaloshinskii-Moriya, DM)상호작용은 교환 상호작용의 한 종류로, 하이젠베르크 교환 상호작용과 다르게 스핀궤도 결합이 큰 물질과 인접한 자기모멘트 사이에서 작용하는 비대칭 교환 상호작용이다. 최근 DM 상호작용은 전류에 의해 동작하는 자구 벽의 이동속도를 현저히 증가시키며, 특히 스핀들이 소용돌이 모양으로 배열되는 자기 스커미온 구조를 형성하는데 중요한 역할을 한다는 것이 보고되었다. 자기 스커미온은 저전력, 고밀도, 초고속으로 구동 할 수 있다는 예측과 준입자 상태를 갖는다는 장점으로 차세대 자기메모리로 각광받고 있는 스핀궤도 돌림힘 기반 자기메모리 소자를 비롯하여 미래의 스핀트로닉스 소자의 중요한 후보로 대두되고 있다. 이러한 이유로 안정적인 자기 스커미온을 형성하기 위해 DM 상호작용과 수직 자기이방성에 대한 연구는 매우 중요하다. 이론적으로 안정적인 자기 스커미온 형성은 DM 상호작용을 갖는 자구 벽 에너지 밀도가 0 혹은 음수가 되는 것을 선호한다. 현재까지 다양한 방법으로 DM 상호작용을 측정하는 기술이 개발되었으며, 관련 연구도 활발히 진행되고 있다. 본 논문은 중금속/강자성 다층 자기박막의 구조에서 중금속층의 강력한 스핀궤도 결합으로 얻은 DM 상호작용과 수직 자기이방성의 물리적 현상에 초점을 맞추어 수행되었다. 물리적 현상을 조사하기 위해 브릴루앙 광 산란 (Brillouin light scattering) 방법이 주요하게 이용되었다. 이 측정방법은 입사하는 빛을 이용하여 열적으로 들뜬 스핀파를 조사하여 DM 상호작용, 수직 자기이방성, 포화 자화, 교환 뻣뻣함 상수, 자기 감쇠 상수 등 기본적인 자기적 특성을 동시에 측정할 수 있는 다목적 측정도구이다. 본 논문은 크게 두 가지의 주요한 연구를 수행한다. 첫 번째 연구는 스핀궤도 상호작용의 물리적 현상을 관측하기 위해 마그네트론 스퍼터링 시스템을 이용하여 구조적으로 동일하지만, 물질의 적층 순서가 역전된 Pd/Co/Pt과 Pt/Co/Pd의 시료를 제작하여 수행하였다. 실험결과 증착 순서에 따라서 수직 자기이방성이 크게 감소함을 실험적으로 관측하였다. 이 현상은 스퍼터를 이용하여 물질의 증착 순서에 따라서 침투하는 정도가 다르고, 이에 따라서 혼합이 일어나는 정도가 달라지는 것으로 해석할 수 있다. 하지만 수직 자기이방성의 극적인 변화에도 DM 상호작용 에너지 밀도는 크게 변화하지 않는 다는 것을 실험적으로 관측하였다. 실험결과를 기반으로 외부자기장이 없는 환경에서 Pd/Co/Pt 구조는 특정한 Co 두께에서 자구 벽 에너지 밀도가 음수가 되는 영역을 갖는다는 것을 계산을 통하여 증명하였다. 두 번째 연구는 신뢰성 있는 DM 상호작용 에너지 밀도 결정과 관련이 있다. DM 상호작용을 관측하기 위하여 브릴루앙 광 산란 분광계는 필수적으로 요구되는 장비이다. 근본적인 비대칭 교환상호작용을 조사하기 위하여, 계면 쟐로신스키-모리야 상호작용 에너지 밀도의 정확하고 신뢰할 수 있는 정량적 측정방법이 요구된다. 하지만 측정하는 시료의 거칠기 및 계면의 구조적인 형태에 따라서 자성층 계면에서 스핀파의 형성이 어려운 경우가 있으며, 이는 스핀파의 신호 대 잡음비 (signal-to-noise ratio, SNR)가 낮은 실험결과를 초래한다. SNR이 낮은 경우 다양한 물리적 특성을 정확하게 분석하기 어렵다. 이러한 실험적 한계를 극복하기 위해 자기광학 학계에서 잘 알려진 방법인 무반사 코팅 (Anti-reflection coating)을 이용하여 스핀파의 크기를 획기적으로 증가시켰다. 물질 간 계면에서 일어나는 다중반사와 반전대칭이 깨진 구조를 위해 무반사 층으로 MgO를 사용되었다. 이 연구를 통하여 무반사 코팅을 이용하여 신뢰성 있는 DM 상호작용 에너지 밀도 측정을 실험적으로 증명하였다. 본 연구는 상온에서 외부 자기장 인가없이 간단한 구조의 자성박막에서 자기 스커미온을 형성하는 새로운 방법을 제시하였고, 자기 스커미온 생성과 관련하여 주요한 물질의 특성인 DM 상호작용 에너지 밀도의 신뢰성 있는 결정방법을 제안하였다. 이 결과는 현재 활발히 연구되고 있는 스핀궤도 돌림힘 기반 자기메모리 소자와 자기 스커미온 기반 소자의 응용연구에 도움이 될 것으로 기대된다.YⅠ. Introduction 1 Ⅱ. Theoretical backgrounds 10 2.1 Exchange interaction 10 2.1.1 Heisenberg exchange interaction 10 2.1.2 Dzyaloshinskii-Moriya interaction 13 2.2 Magnetic anisotropy energy 15 2.2.1 Magneto-crystalline anisotropy 15 2.2.2 Shape magnetic anisotropy 17 2.2.3 Interfacial magnetic anisotropy 20 2.2.4 Perpendicular magnetic anisotropy 21 2.3 The other magnetic energies 23 2.3.1 Zeeman energy 24 2.3.2 Landau-Lifshitz-Gilbert equation 24 2.4 Spin wave 28 2.4.1 Basic concept of spin wave 28 2.4.2 Spin waves in the single magnetic thin film 33 2.5 Inelastic light scattering 37 2.5.1 Mechanism of inelastic scattered light 37 2.5.2 Brillouin light scattering 39 Ⅲ. Fabrication process and Experiment tools 42 3.1 Sample fabrication process 42 3.1.1 Magnetic multilayer deposition 42 3.1.2 Lithography techniques 45 3.1.3 Fabrication patterning process 47 3.2 Brillouin light scattering spectroscopy 49 3.2.1 Fabry-Pérot interferometer 49 3.2.2 Tandem Fabry-Pérot interferometer (TFPI) 55 3.2.3 Setup of Brillouin light scattering spectroscopy system 58 3.3 Magneto-optical Kerr effect 63 3.3.1 Background of Magneto-optical Kerr effect 63 3.3.2 Setup of Laser-Magneto-optical Kerr effect system 67 3.3.3 Automatically controlled z-axis stage for Wedge-type thin films 68 3.3.4 Customized sample holder with printed circuit board 70 3.4 SQUID-VSM measurements 71 Ⅳ. Result and discussion 1 73 4.1 Overview 73 4.2 Introduction 74 4.3 Sample fabrication and Experimental details 76 4.4 Experimental results and discussion 82 4.5 Find to nucleate the magnetic skyrmion state 89 4.5.1 Approach for numerical calculation 89 4.5.2 Approach for micromagnetic simulation 92 4.6 Summary 95 Ⅴ. Result and discussion 2 97 5.1 Overview 97 5.2 Introduction 98 5.3 Physical mechanism and experimental details 101 5.4 Experimental results and discussion 106 5.5 Summary 114 Ⅵ. Conclusion 115 Ⅶ. References 117 국문요약 130DoctordCollectio

PM_2.5 Concentration Forecasting Using Weighted Bi-LSTM and Random Forest Feature Importance-Based Feature Selection

Particulate matter (PM) in the air can cause various health problems and diseases in humans. In particular, the smaller size of PM2.5 enable them to penetrate deep into the lungs, causing severe health impacts. Exposure to PM2.5 can result in respiratory, cardiovascular, and allergic diseases, and prolonged exposure has also been linked to an increased risk of cancer, including lung cancer. Therefore, forecasting the PM2.5 concentration in the surrounding is crucial for preventing these adverse health effects. This paper proposes a method for forecasting the PM2.5 concentration after 1 h using bidirectional long short-term memory (Bi-LSTM). The proposed method involves selecting input variables based on the feature importance calculated by random forest, classifying the data to assign weight variables to reduce bias, and forecasting the PM2.5 concentration using Bi-LSTM. To compare the performance of the proposed method, two case studies were conducted. First, a comparison of forecasting performance according to preprocessing. Second, forecasting performance between deep learning (long short-term memory, gated recurrent unit, and Bi-LSTM) and conventional machine learning models (multi-layer perceptron, support vector machine, decision tree, and random forest). In case study 1, The proposed method shows that the performance indices (RMSE: 3.98%p, MAE: 5.87%p, RRMSE: 3.96%p, and R2:0.72%p) are improved because weights are given according to the input variables before the forecasting is performed. In case study 2, we show that Bi-LSTM, which considers both directions (forward and backward), can effectively forecast when compared to conventional models (RMSE: 2.70, MAE: 0.84, RRMSE: 1.97, R2: 0.16). Therefore, it is shown that the proposed method can effectively forecast PM2.5 even if the data in the high-concentration section is insufficient

Architectural Supports to Protect OS Kernels from Code-Injection Attacks and Their Applications

The kernel code injection is a common behavior of kernel-compromising attacks where the attackers aim to gain their goals by manipulating an OS kernel. Several security mechanisms have been proposed to mitigate such threats, but they all suffer from non-negligible performance overhead. This article introduces a hardware reference monitor, called Kargos, which can detect the kernel code injection attacks with nearly zero performance cost. Kargos monitors the behaviors of an OS kernel from outside the CPU through the standard bus interconnect and debug interface available with most major microprocessors. By watching the execution traces and memory access events in the monitored target system, Kargos uncovers attempts to execute malicious code with the kernel privilege. On top of this, we also applied the architectural supports for Kargos to the detection of ROP attacks. KS-Stack is the hardware component that builds and maintains the shadow stacks using the existing supports to detect this ROP attacks. According to our experiments, Kargos detected all the kernel code injection attacks that we tested, yet just increasing the computational loads on the target CPU by less than 1% on average. The performance overhead of the KS-Stack was also less than 1%

Fast Hardware-Software Coverification by Optimistic Execution of Real Processor

To achieve fast verification of the software part of embedded system, we propose to run the target processor optimistically, which effectively reduces the synchronization overhead with other simulators. For the optimistic processor execution, we present a processor execution platform and state saving/restoration methods. We performed optimistic execution of ARM710A processor in the coverification of an IS-95 CDMA cellular phone system and obtained up to orders of magnitude higher performance compared with the case that the processor runs conservatively. 1. Introduction Verification of system functionality and timing is one of the most difficult and important aspects of System on a Chip (SoC) design. For many system design teams, verification takes 50% to 80% of the overall system design effort [1]. For fast verification of the hardware part of the system being designed, cycle-based simulators and high performance emulation systems have been widely used. For the verification of the s..