경매이론의 관점에서 본 신용평가 산업의 경쟁분석

학위논문 (석사) -- 서울대학교 대학원 : 사회과학대학 경제학부, 2021. 2. 김진우.We build a model including the aspect of ratings shopping, ratings catering, and resulting rating inflation. Especially, we adopt the setting of first price auction to show the effects of competition among credit rating agencies to rating inflation. The analysis of benchmark model reveals that there is uniform rating inflation if issuers can provide high enough reward to the winning credit rating agency. In addition, rating inflation worsens when there are more competing credit rating agencies. After analyzing the benchmark model, we explore implication of adopting stricter disclosure requirement and ‘investor pays’ model. Both proposals have similar advantage that the cost of issuers' inducing uniform rating inflation becomes expensive. Yet, these policies also share the same weakness that the issuers with sufficient financial resource are not affected. Nonetheless, there is a chance of recovering investors' loss in the case of investor pays model by giving more information to them. However, if investor pays model results overly pessimistic view on average financial products, securities with high success probability can be crowded out from the market. Lastly, we study hypothetical circumstance where legal penalty is given to winning credit rating agency which reported untruthfully, and figure out the range of penalty that can guarantee strategy-proofness.본 논문에서는 신용등급 쇼핑, 신용등급 케이터링, 신용등급 인플레이션을 모두 포함하는 모델을 설계한다. 특히 최고가격경매의 모델을 통해 신용평가사들 간의 경쟁이 신용등급 인플레이션에 미치는 영향을 분석할 것이다. 기본 모델의 분석은 채권발행자들이 신용평가사에 충분히 높은 보상을 제공할 수만 있다면 균일한 신용등급 인플레이션을 유도할 수 있다는 것을 보여준다. 또한 이러한 신용등급 인플레이션은 경쟁하고 있는 신용평가사들의 수가 많을수록 심해지는 경향이 있다. 기본 모델의 분석에 이어서 본 논문에서는 강력한 의무공개 조항과 투자자 지급 모형의 도입이 가지는 함의에 대해 알아볼 것이다. 두 정책 모두 채권발행자가 균일한 신용등급 인플레이션을 유도하는 비용을 높여준다는 장점이 있다. 그러나 동시에 채권발행자가 충분한 자본력을 가지고 있으면 정책이 무력화된다는 약점도 공유한다. 그럼에도 불구하고 투자자 지급 모형의 경우 투자자들에게 더 많은 정보를 제공함으로써 투자자의 손실을 줄여줄 가능성이 있다. 그러나 한편으로 이 과정에서 투자자들이 지나치게 비관적인 전망을 가지게 될 경우, 금융시장에서 건전한 상품들이 구축되는 결과가 나올 위험도 있다. 끝으로 본 논문에서는 거짓된 신용등급을 보고한 신용평가사에 법적 처벌이 주어지는 가상적인 환경을 연구함으로써 대전략성이 보장되는 법적 처벌 정도의 범위를 도출한다.Chapter 1 1 Section 1 1 Section 2 4 Chapter 2 7 Section 1 8 Section 2 12 Chapter 3 14 Section 1 14 Section 2 17 Section 3 20 Chapter 4 Conclusion 24 References 26 국문초록 29Maste

양자정보이론에서의 추상조화해석학

학위논문(박사) -- 서울대학교대학원 : 자연과학대학 수리과학부, 2023. 8. 이훈희.This Ph.D. thesis delves into the fascinating realm of quantum information theory, employing methods from abstract harmonic analysis. The research is organized into two parts, each focusing on independent topics, based on the research results during the authors doctoral studies [BCL+22, PJPY23, PY23]. In the first part, our primary objective is to present an abstract definition of Gaussian states, inspired by the intriguing mathematical connections between bosonic Gaussian states and stabilizer states. To achieve this, we leverage the phase space formulation, considering a locally compact abelian group (LCA) with a proper symplectic structure as the abstract phase space. Within this framework, we naturally define the Weyl unitary operators and characteristic functions. The Gaussian states are then defined through the concept of Gaussian distributions on LCA groups in the sense of Bernstein. Remarkably, this definition establishes a universal framework that unifies many important notions in quantum theory as well as simultaneously explaining bosonic Gaussian states and stabilizer states. Moreover, we justify our definition by showing that pure Gaussian states over a phase space derived from a totally disconnected LCA group can be characterized by the non-negativity of their Wigner quasi-distribution. This result can be interpreted as an analog of Hudsons theorem and a generalization of Grosss result. In the second part, we develop a theory of quantum entanglement under the symmetry with respect to unitary representations of compact groups. Quantum entanglement plays a vital role as a valuable resource in quantum information processing, and significant efforts have been dedicated to unraveling the mathematical structure of entanglement in recent years. While the general dualities between mapping cones introduced by Størmer can describe various notions related to quantum entanglement, they are not sufficient to effectively deal with entanglement due to the computational hardness of testing entanglement. In this thesis, we show that such duality results carry over into the framework of compact group symmetry. This directly leads to two applications in quantum information theory: (1) the optimization of entanglement witnesses and Schmidt number witnesses, and (2) the equivalence between the problem of PPT=separability and the problem of checking whether every extremal positive map is completely positive or completely copositive under compact group symmetry. The merits of our proposed framework are showcased through detailed analyses of examples, which solve various open problems related to quantum entanglement.본 학위논문에서는 추상조화해석학에서의 방법론을 적용하여 양자정보이론의 흥미 로운 영역들을 들여다 보고자 한다. 본 논문의 구성은 저자의 학위과정 중 연구결과 [BCL+22, PJPY23, PY23]에 기반하여, 독립적인 주제를 담고 있는 두 개의 파트로 나누어 볼 수 있다. 첫 번쨰 파트에서는 가우시안상태와 안정자상태 (stabilizer state)가 흥미로운 수학적 유사성을 가짐에 착안하여, 일반화 된 가우시안상태의 정의를 제안하는것이 주된 목표이다. 이를 위해, 적당한 사교구조를 가진 국소컴팩트가환군 (LCA (locally compact abelian) 군)을 물리적 위상공간 (phase space)으로 사용하는 추상위상공 간을 생각한다. 이러한 프레임워크 내에서 우리는 일반화 된 Weyl 유니터리 작용소 및 양자특성함수를 자연스럽게 정의할 수 있다. 그러고나면 LCA 군 위에서 정의된 여러가지 가우시안 분포의 모델 중 Bernstein 방식을 적용하여 추상적인 가우시 안상태를 정의해 볼 수 있다. 놀랍게도 이러한 추상적 가우시안상태는 보존가우시 안상태 및 안정자상태 뿐 아니라 양자이론에 등장하는 여러가지 중요한 개념들을 어우르는 보편적인 방식을 제공해 준다. 그 뿐 아니라, 위상공간이 완전분리 (totally disconnected) LCA 군으로부터 비롯된 경우, 순수가우시안상태는 각각의 Wigner 준 확률분포 (quasi-distribution)가 확률분포를 이룬다는 성질로부터 완전히 특정지을 수 있게 된다. 이는 보존시스템에서의 Hudson 정리를 다른 종류의 위상공간에서 얻은 것으로 볼수 있어 가우시안상태라는 명칭에 또 하나의 정당성을 부여해 준다. 또한 위 결과는 Gross의 결과를 일반화 한 것이기도 하다. 두 번째 파트에서는 컴팩트군 표현에 대한 대칭성 하에서의 양자얽힘이론을 다 룬다. 양자얽힘은 양자정보프로세에서의 핵심적인 자원 역할을 하고, 최근 몇 년간 양자얽힘의 수학적 구조를 파악하기 위해 수많은 노력이 이루어져 왔다. 일반적으로 Størmer가 도입한 사상콘 (mapping cone) 사이의 쌍대성으로부터 양자얽힘과 관련된 많은 개념들을 설명할수 있음에도, 양자얽힘 자체에 대한 계산복잡도적인 어려움으로 인해 이를 효과적으로 다루는 것은 쌍대성만으로는 충분하지 않다. 본 학위논문에서 는 이러한 쌍대성이 일반적인 상황 뿐 아니라 컴팩트군 대칭성을 부여하였을때에도 잘 적용된다는 사실을 살펴본다. 이 관찰로부터 다음의 두 가지 중요한 결과를 얻을 수 있다: 컴팩트군 대칭 하에서의 (1) 얽힘 관측기 (entanglement witness) 및 슈미트수 관측기 (Schmidt number witness) 사용의 최적화, (2) PPT=얽힘 문제와 양사상= 분해가능사상 문제의 동치성. 위 결과를 적용하여 양자얽힘과 관련된 여러가지 구체 적인 사례분석과 더불어 다양한 난제를 해결해 줄 수 있었는데, 이러한 점에서 우리의 결과가 단순 이론에 그치지 않고 강력한 이점이 있음을 알아보도록 한다Abstract i Contents iii 1 Introduction 1 2 Preliminaries 7 2.1 Abstract harmonic analysis 7 2.1.1 Locally compact abelian groups and Fourier analysis 8 2.1.2 Compact groups and invariant operators 13 2.2 Quantum entanglement 14 2.2.1 Separability and PPT property 14 2.2.2 Schmidt number and positive maps 16 3 Abstract Gaussian states 20 3.1 Preliminaries on general quantum kinematical systems 23 3.1.1 Phase space structure 23 3.1.2 Weyl systems 25 3.1.3 Fermions and hardcore bosons 29 3.2 Characteristic and Wigner functions of quantum states 33 3.3 Gaussian states in general quantum kinematical systems 39 3.4 Weyl systems over 2-regular groups 44 3.4.1 Systems admitting compact open subgroups 45 3.4.2 General 2-regular systems 54 3.4.3 Pure Gaussian states 56 3.5 Angle-number systems 63 3.6 Fermions and hard-core bosons 65 3.7 Hudson's theorem for 2-regular totally disconnected groups 67 4 Mapping cone and compact group symmetry 77 4.1 General theory of mapping cones 78 4.2 Group symmetry methods 80 4.2.1 Compact group symmetry and Twirling operations 80 4.2.2 Duality between mapping cones under compact group symmetry 85 4.3 Entanglement under symmetry 90 5 Applications to quantum entanglement 94 5.1 Hyperoctaheral group symmetry and entanglement detection 94 5.1.1 Covariant positive maps with respect to monomial unitary groups 102 5.2 k-positivity and Schmidt number under Orthogonal group symmetry 104 5.2.1 k-positivity of orthogonally covariant maps 105 5.2.2 Schmidt numbers of orthogonally invariant quantum states 111 5.3 Tripartite systems with unitary group symmetries 123 5.3.1 Tripartite Werner states 124 5.3.2 Tripartite quantum orthogonally invariant quantum states 129 5.4 Appendix for Section 5.3 134 5.4.1 Characterization of Inv(U 3 ) PPT 134 5.4.2 Extremal positive maps 135 5.4.3 Proof of Theorem 5.3.6 when d = 2 141 5.4.4 Quantum orthogonal symmetry 143 Bibliography 145 Abstract (in Korean) 161 Acknowledgement (in Korean) 163박

Comparison of Temperature and Pain Changes between the Drip and Topical Methods of Administering the Transnasal Sphenopalatine Ganglion Block

The objective of this study was to compare facial temperatures and the visual analogue scale (VAS) between the drip method and the topical method of transnasal sphenopalatine ganglion block (SPGB). The transnasal SPGB is administered to patients with facial or head and neck pain. In the transnasal approach, the drip and topical methods are frequently used. We compared facial temperatures and VAS after transnasal SPGB. Medical records of 74 patients who visited the pain clinic and underwent transnasal SPGB were retrospectively reviewed. A total of 156 transnasal SPGB were performed. The patients were divided into the drip-method and topical-method groups. Facial temperatures were measured in six areas of the right and left forehead, maxilla, and mandible before and 30 min after completion of the transnasal SPGB. Temperatures were compared before and 30 min after SPGB in each group and between the two groups. VAS scores were compared at the same times of SPGB in each group and between the two groups. In the drip-method group, there were significant increases at four areas of the face in temperature changes at 30 min after SPGB. In the topical-method group, there was no significant difference in the temperature changes at 30 min after SPGB. There were statistically significant differences in the facial temperature changes between the two groups in the right forehead (p = 0.001), left forehead (p = 0.015), and right maxillary area (p = 0.046). In herpes zoster, there were statistically significant differences in the VAS scores between before and 30 min after SPGB in both groups (p < 0.001, p = 0.008) and between two groups (p < 0.001). In migraine, there were statistically significant differences in VAS scores between before and 30 min after SPGB in both groups (p < 0.001, p = 0.004) and between two groups (p = 0.014). Transnasal SPGB using two methods showed different temperature changes and VAS scores.ope

Reasons for failure to perform interventional pain procedures in cancer patients: an analysis of pain clinic consultations

Background: Interventional pain procedures (IPPs) may be necessary for some cancer patients when conservative treatment fails. However, many IPPs are often delayed or cancelled for cancer patients who are referred to the pain clinic. Methods: We retrospectively analyzed the reasons for such cancellations to identify clinically avoidable causes of the delay in IPP. Results: We enrolled 350 cancer patients who were referred to our pain clinic for an IPP between March 2016 and February 2018. There were 213 (60.9%) cases that were cancelled, among which 115 (54%) cases were potentially avoidable and 98 (46%) were unavoidable. The most common reasons for cancellation were patient-derived factors, which accounted for 85 (39.9%) cases. Patient refusal was a common reason for cancellation, with 33 (15.5%) cases attributed to this cause. The primary avoidable causes of cancellation were a recommendation that the patient continue with their current pharmacological pain treatment, conflict with another planned treatment, and pain characteristics that were not suitable for an IPP. Together, these accounted for 76.5% of all avoidable cancellations. Conclusions: Comprehensive and accurate pain assessments before IPP may result in more favorable outcomes for the efficient use of medical resource and effective pain relief in cancer patients.ope

수송물류결절점 평가기법 연구

현재 우리나라의 물류전략의 기본방향은 거점별 물류시스템 구축이라는 전제하에 시설공급 위주로 설정되어 있으며, 향후 동북아 물류중심지를 위한 각 물류거점의 기능과 역할에 대한 규정은 제대로 정립되어 있지 못한 실정이다. 특히 수송물류결절점에 대한 객관적인 평가방법에 대한 기초연구가 부족하고, 물류부문에서 주요 관심사인 수단간 연계까지 고려한 객관적 평가방법은 전무하다고 할 수 있다. 따라서 향후 동북아 물류중심지 역할에 상응하고 효율적인 물류시스템 구축을 위해서는 물류시설 공급계획과 함께 거점별 운영전략도 통합·수립되어야 한다. 우선 그 첫걸음으로 객관적 기준을 적용한 물류거점 및 주요 수송물류결절점에 대한 평가와 함께 평가결과 도출된 기능과 역할을 수행할 수 있도록 시설공급계획 및 운영전략기준을 마련해야 할 것이다. 본 연구는 최근 주목을 받고 있고 정량적 요소와 정성적 요소를 통합하여 평가를 할 수 있는 의사결정방법론인 AHP방법론을 이용하여 주요 물류결절점을 평가하는 방법을 개발하는 것을 목적으로 하고 있다. 그리고 시간 및 계량적 자료의 제약으로 비록 계량적 자료를 사용하지는 않지만 개발한 방법론을 3개 지역에 모형을 적용하여 그 적정성을 검증하는 것을 목적으로 하고 있다

Factors Associated with Higher Reported Pain Levels in Patients with Chronic Musculoskeletal Pain: A Cross-Sectional, Correlational Analysis

BACKGROUND: Chronic musculoskeletal pain is highly prevalent, disabling, and costly, and has many negative effects on quality of life. The aim of this study was to investigate factors associated with higher reported pain levels in patients with chronic musculoskeletal pain among demographic, clinical, and psychological factors, and to evaluate whether insomnia is independently associated with pain intensity in this population. METHODS: A total of 357 patients with chronic musculoskeletal pain (pain duration ≥ six months) satisfied the study inclusion criteria and were included in the analyses. Patient demographics, clinical, and psychological factors were evaluated with hierarchical multivariate logistic analysis to identify factors associated with severe pain (NRS [numeric rating scale] ≥ 7). Hierarchical linear regression analysis also performed to identify factors associated with pain intensity (0 to 10 NRS). RESULTS: Multivariate logistic analyses revealed older age (OR [odds ratio] = 1.017, 95% CI [confidence interval] 1.001-1.032, P = 0.034), high anxiety level (OR = 1.162, 95% CI 1.020-1.324, P = 0.024), high pain catastrophizing (OR = 1.043, 95% CI 1.007-1.081, P = 0.018), and severe insomnia (OR = 1.112, 95% CI 1.057-1.170, P<0.001) were significantly associated with severe pain. Hierarchical linear regression analysis showed age (β = 0.106, P = 0.041), pain catastrophizing (β = 0.249, P<0.001), and insomnia (β = 0.286, P<0.001) were significantly associated with pain intensity. The variance in pain intensity explained by the final model was 32.2%. CONCLUSIONS: Older age, severe insomnia, and high pain catastrophizing were significantly associated with higher reported pain levels. Insomnia was independently associated with pain intensity, even after controlling for various demographic and clinical factors. These factors should be considered when devising pain management strategies for this population.ope

Predictors of the analgesic efficacy of pulsed radiofrequency treatment in patients with chronic lumbosacral radicular pain: a retrospective observational study

Background: Pulsed radiofrequency (RF) targeting the adjacent dorsal root ganglion (DRG) is one treatment option for lumbosacral radicular pain. However, the analgesic efficacy of this procedure is not always guaranteed. The aim of this retrospective study was to identify the predictors of the analgesic efficacy of pulsed DRG RF treatment in patients with chronic lumbosacral radicular pain. Methods: Patients who underwent pulsed DRG RF treatment from 2006 to 2017 at our clinic were enrolled. Positive response was defined as a >/=50% reduction in pain score from baseline at day 30. Patient demographics, pain-related factors, and clinical factors were evaluated using logistic regression analysis to identify the predictors of a positive response to the treatment. Results: A total of 60 patients satisfied the study protocol requirements. Twenty-eight patients (46.7%) had a positive outcome. Multivariate logistic regression analysis revealed that the absence of comorbid musculoskeletal pain (OR=0.518, 95% CI=0.029-0.858, P=0.033) and positive response to previous epidural steroid injection (OR=3.269, 95% CI=1.046-10.215, P=0.042) were independent predictors of the analgesic efficacy of pulsed DRG RF treatment. Conclusion: Comorbid musculoskeletal pain and previous epidural injection response appear to affect the outcome of pulsed DRG RF treatment in patients with chronic lumbosacral radicular pain.ope

Influence of Handgrip Strength and Psoas Muscle Index on Analgesic Efficacy of Epidural Steroid Injection in Patients With Degenerative Lumbar Spinal Disease

Background: Handgrip strength (HGS) and psoas muscle index (PMI) are widely used protocols for screening or diagnosing sarcopenia by measuring muscle strength and mass. Epidural steroid injection (ESI) is a common intervention for the treatment of spinal pain; however, the influence of pre-procedural sarcopenic status on therapeutic effects after ESI has not been investigated. Objectives: In the present study, whether pre-procedural HGS or PMI predicts analgesic efficacy of ESI in elderly patients with degenerative lumbar spinal disease was investigated. Study design: This was a retrospective observational study. Setting: The study included patients from the outpatient department for interventional pain management at a university hospital. Methods: Following institutional review board (IRB) approval, patients &gt;= 65 years of age who underwent fluoroscopy-guided lumbar ESI from 2016 to 2017 in our clinic were enrolled in the present study. Good analgesia was defined as &gt;= 50% reduction in pain score at 4 weeks after injection. Patient characteristics, pain-related factors, clinical factors, HGS, and PMI measurements were collected and analyzed using multivariate analysis to identify the predictors of good analgesia after lumbar ESI. In addition, a receiver operating characteristic curve (ROC) analysis was performed, and area under the curve (AUC) values with 95% confidence interval (CI) were calculated for the HGS. Results: A total of 259 patients satisfied the study protocol requirements. HGS was significantly higher in the good analgesia group (23.12 ± 7.54 vs 16.55 ± 6.66 kg, P &lt; 0.001). However, the PMI did not differ between the 2 groups (5.25 ± 1.55 vs 5.08 ± 1.69 cm2/m2, P = 0.406). Multivariate analysis revealed higher HGS (odds ratio, OR = 1.142, 95% CI = 1.094-1.193, P &lt; 0.001) and low-grade foraminal stenosis (OR = 0.403, 95% CI = 0.199-0.814, P = 0.011) were significantly associated with good analgesia after injection. The AUC values with 95% CI for HGS were 0.819 (0.718-0.920) in men and 0.800 (0.732-0.869) in women. In addition, HGS cutoff values for predicting good analgesic outcomes were 26.5 kg in men and 16.5 kg in women. Limitations: This study was conducted in a single center, and sample size was relatively small. The lack of physical performance evaluation did not fully meet the current criteria for sarcopenia. In addition, post-procedural clinical data associated with disability or quality of life could not be collected. Conclusion: In the present study, pre-procedural HGS was an independent predictor of analgesic efficacy after ESI in elderly patients with degenerative lumbar spinal disease. However, the PMI was not associated with pain relief after injection.ope

Comparison of Incidences of Intravascular Injection between Medial and Lateral Side Approaches during Traditional S1 Transforaminal Epidural Steroid Injection

Purpose : Intravascular injection rates are higher during traditional S1 transforaminal epidural steroid injection (TFESI) compared with lumbar transforaminal injection. We compared the incidences of intravascular injection between the medial and lateral approaches to the S1 foramen during S1 TFESI. Materials and Methods : A total of 139 patients underwent one or more TFESIs (170 total injections). The patients received S1 TFESI by either medial or lateral side of S1 foramen under fluoroscopic anteroposterior view using digital subtraction method. The intravascular injection rates, epidural spread patterns, and contrast volumes required to reach the superior aspect of the L5-S1 intervertebral disc (SIVD) were compared between groups. Results : Intravascular injection rates during S1 TFESI were significantly lower in the medial approach compared with the lateral approach patients (4.9% versus 38.6%, resp., P < 0.001). The medial approach group had more epidural spread to the L5-S1 SIVD than the lateral group (82.1% versus 58.8%, resp.); lower contrast volume amounts were required to extend the L5-S1 SIVD (1.46 ± 0.48 versus 1.90 ± 0.62, resp.). Conclusion : During S1 TFESI, approaching the needle towards the medial part of the S1 foramen may reduce intravascular injection risk.ope

Clinical Effectiveness of Ultrasound-guided Costotransverse Joint Injection in Thoracic Back Pain Patients

Because of its anatomical location and function, the costotransverse (CTRV) joint can be a source of thoracic back pain. In this retrospective observational study, we evaluated the clinical effectiveness of the CTRV joint injection in thoracic back pain patients with suspected CTRV joint problems. We enrolled 20 thoracic back pain patients with localized tenderness that was provoked by the application of pressure on the affected CTRV joints. We injected it with 0.5 ml of a ropivacaine and triamcinolone mixture at each level. The mean pre-injection pain score decreased by 37.9% (7.2 ± 1.5 to 4.5 ± 1.7, P < 0.001) two weeks after CTRV joint injection. In addition, 70% of patients reported an excellent or good level of satisfaction. We demonstrated that an ultrasound-guided injection of the CTRV joint reduced patients' pain scores and led to a high level of satisfaction at short-term follow-ups in patients with suspected CTRV joint problems.ope