낸드 플래시 메모리 신뢰도 향상을 위한 신호 처리 방법 연구

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2014. 2. 성원용.The capacity of NAND flash memory has been continuously increased by aggressive technology scaling and multi-level cell (MLC) data coding. However, it becomes more challenging to maintain the current growth rate of the memory density mainly because of degraded signal quality of sub-20 nm NAND flash memory. This dissertation develops signal processing techniques to improve the signal reliability of MLC NAND flash memory. In the first part of this dissertation, we develop two threshold voltage distribution estimation algorithms to compensate the effect of program-erase (PE) cycling and charge loss in MLC NAND flash memory. The sensing directed estimation (SDE) utilizes the output of multi-level memory sensing to estimate the means and the variances of the threshold voltage distribution that is modeled as a Gaussian mixture. In order to reduce memory sensing overheads for the SDE algorithm, we develop a decision directed estimation (DDE) that uses error corrected bit patterns for more frequent updates of the model parameters. We also present a combined estimation scheme that employs both the SDE and the DDE approaches to minimize the number of memory sensing operations while maintaining the estimation accuracy. The effectiveness of the SDE and the DDE algorithms is evaluated by using both simulated and real NAND flash memory, and it is demonstrated that the proposed algorithms can estimate the statistical information of threshold voltage distribution accurately. The cell-to-cell interference (CCI) is one of the major sources of bit errors in sub-20 nm NAND flash memory and becomes more severe as the size of memory cell decreases. In the second part of this dissertation, we develop a CCI cancellation algorithm that is similar to interference cancellers employed in conventional communication systems. We first provide the experimental characterization of the CCI by measuring the coupling coefficients from actual NAND flash memory with a 26 nm process technology. Then, we present a CCI cancellation algorithm that consists of the coupling coefficient estimation and the CCI removal steps. To reduce the number of memory sensing operations, the optimal quantization schemes for the proposed CCI canceller are also studied. This dissertation also develops soft-information computation schemes in order to apply soft-decision error correction to NAND flash memory. The probability density function (PDF) of the CCI removed signal is quite different from that of the original threshold voltage, which can be modeled as a Gaussian mixture. Thus, computing soft-information, such as LLR (log likelihood ratio), with the CCI removed signal is not straightforward. We propose two soft-information computation schemes that combine CCI cancellation and soft-decision error correction. In the first approach, we derive a mathematical formulation for the PDF of the CCI removed signal and directly compute the LLR values by using it. In the second approach, CCI cancellation and soft-information computation are jointly conducted. Based on the intensive simulations, it is demonstrated that the reliability of NAND flash memory is significantly improved by applying the proposed signal processing algorithms as well as soft-decision error correction.1 Introduction 14 2 NAND Flash Memory Basics 19 2.1 Basics of NAND Flash Memory 19 2.1.1 NAND Flash Memory Structure 19 2.1.2 Multi-Page Programming 20 2.1.3 Cell-to-Cell Interference 22 2.1.4 Data Retention 23 2.2 Threshold Voltage Distribution of NAND Flash Memory and Signal Modeling 25 2.2.1 Threshold Voltage Distribution and Gaussian Approximation 25 2.2.2 Modeling of Threshold Voltage Signal 27 3 Threshold Voltage Distribution Estimation 31 3.1 Introduction 31 3.2 Sensing Directed Estimation of Threshold Voltage Distribution 33 3.2.1 Cost Function 34 3.2.2 Gradient Descent Method based Parameter Search 36 3.2.3 Levenberg-Marquardt Method based Parameter Search 38 3.2.4 Experimental Results 41 3.3 Decision Directed Estimation of Threshold Voltage Distribution 50 3.3.1 Basic Idea 51 3.3.2 Applying to Two-Bit MLC NAND Flash Memory 54 3.3.3 Combined Threshold Voltage Distribution Estimation 57 3.3.4 Error Analysis 58 3.3.5 Experimental Results 64 3.4 Concluding Remarks 70 4 Cell-to-Cell Interference Cancellation 71 4.1 Introduction 71 4.2 Direct Measurement of Coupling Coefficients 73 4.2.1 Measurement Procedure 74 4.2.2 Experimental Results 77 4.3 Least Squares Method based Coupling Coefficient Estimation 83 4.4 Multi-Level Memory Sensing Schemes for CCI Cancellation 87 4.5 Experimental Results 91 4.5.1 CCI Cancellation with Simulated NAND Flash Memory 91 4.5.2 CCI Cancellation with Real NAND Flash Memory 96 4.6 Concluding Remarks 97 5 Soft-Decision Error Correction in NAND Flash Memory 99 5.1 Introduction 99 5.2 Soft-Decision Error Correction without CCI Cancellation 101 5.3 Soft-Decision Error Correction with CCI Cancellation 104 5.3.1 Soft-Information Computation using PDF of CCI Removed Signal 104 5.3.2 Joint CCI Cancellation and Soft-Information Computation 110 5.3.3 Experimental Results 115 5.4 Concluding Remarks 118 6 Conclusion 120Docto

OpenMP based Implementation of Recursive Digital Filters in Multi-core Systems

Direct parallel computation of recursive digital filtering equations is not allowed due to the dependency problem caused by feedback. An efficient parallel block processing program for recursive digital filtering equations is developed using OpenMP API for multi-core systems. This program can achieve the processing speed that is almost proportional to the number of cores.이 논문은 지식경제부 출연금으로 ETRI와 시스템반도체산업진흥센터에서 수행한 ITSoC 핵심설계인력양성사업과 교육과학기술부의 재원으로 한국학술진흥재단에서 수행하는 BK21 프로젝트의 지원을 받아 수행된 연구입니다

The Safety and the Pharmacokinetics and Pharmacodynamics of a Pegylated Interferon Alpha-2a Formulation, Dong-A's DA-3021

Background: Interferons (IFNs) are proteins made and released by lymphocytes in response to the presence of pathogens and used in the treatment of hepatitis B or C virus. The purpose of this study is to investigate the safety, pharmacokinetics and pharmacodynamics of a pegylated interferon alpha-2a formulation. Methods: This study was a randomized, open-label, 2-period, crossover design. Each group had 17 subjects who took $180\;{\mu}g$ of PEGASYS^® as a reference formulation and DA-3021 as a test formulation with a washout period of 21 days. Blood samples were obtained over 336 hours after the dose in each treatment period. Blood concentrations of interferon were analyzed using the enzyme-linked immunosorbent assay (ELISA). The primary pharmacokinetic parameters were Cmax and $AUC_{last}$. The pharmacodynamics were assessed by 2',5'-OAS (oligoadenylate synthetase) using a radioimmunoassay (RIA). The primary pharmacodynamic parameters were $E_{max}$ and $AUE_{last}$. Results: Thirty four healthy male volunteers participated in the study and completed both treatment periods. The 90% confidence intervals for the geometric mean ratios of the pharmacodynamic parameters (test : reference drug) were 0.95-1.09 for $AUE_{last}$ and 0.92-1.05 for $E_{max}$, lying within the bioequivalence range of 0.8-1.25, while the pharmacokinetics parameters were not included within the equivalence range. Most common adverse events were flu-like symptoms, with no serious adverse event reported. Conclusion: The results assessed by the bioequivalence criterion indicated that the pharmacodynamics of DA-3021 was equivalent to that of PEGASYS®.ope

Development of a Pharmacokinetic Interaction Model for Co-administration of Simvastatin and Amlodipine

A model for drug interaction between amlodipine and simvastatin was developed using concentration data obtained from a multiple-dose study consisting of single- and co-administration of amlodipine and simvastatin conducted in healthy Koreans. Amlodipine concentrations were assumed to influence the clearance of simvastatin and simvastatin acid, which as well as the oral bioavailability was allowed to vary depending on genetic polymorphisms of metabolic enzymes. Covariate effects on drug concentrations were also considered. The developed model yielded a 46% increase in simvastatin bioavailability and a 13% decrease in simvastatin clearance when amlodipine 10 mg was co-administered. When CYP3A4/5 polymorphisms were assessed by a mixture model, extensive metabolizers yielded a decrease in simvastatin bioavailability of 81% and a decrease in simvastatin clearance by 4.6 times as compared to poor metabolizers. Sixty percent of the usual dose was the optimal simvastatin dose that can minimize the interaction with amlodipine 10 mg. Age and weight had significant effects on amlodipine concentrations. In conclusion, this study has quantitatively described the pharmacokinetic interaction between simvastatin and amlodipine using a modeling approach. Given that the two drugs are often prescribed together, the developed model is expected to contribute to more efficient and safer drug treatment when they are co-administered.ope

Moderating Role of Leader's Self-Concern or Other-Orientation

학위논문(석사)--서울대학교 대학원 :경영대학 경영학과,2020. 2. 윤석화.최근 가속화되는 시장경쟁, 불확실한 외부환경, 심화되는 업무의 복잡성 및 기술의 발전으로 인해 조직은 구조적인 변화를 직면하고 있다. 현대 조직은 탈 관료제 및 분화된 하위구조, 네트워크 기반 구조 등으로의 변화를 통해 최대 효율성을 취하고자 하며, 이러한 조직의 구조적인 변화는 조직이 변화 무쌍한 외부환경에 효과적으로 적응할 수 있도록 한다. 또한, 현대 조직은, 구조적인 위계질서를 극복하고 이를 통해 구성원들에게 자율성을 부여함으로써 지속 가능한 경쟁우위의 원천인 구성원의 창의성을 증가시킬 수 있다. 이번 연구에는 이러한 사회변화에 조직이 효과적으로 적응 할 수 있는 핵심적인 리더십으로 임파워링 리더십을 선정하였다. 왜냐하면, 임파워링 리더십이 구성원에게 권력을 배분하고, 책임감을 부여하며, 직무의 자율성 보장을 통해 구성원을 보다 창의적인 활동이 가능하도록 여건을 조성해주기 때문이다. 이번 연구에서는 임파워링 리더십이 구성원의 창의적 업무성과에 미치는 효과와, 심리적인 메커니즘에 대해서 본격적으로 다루었다. 먼저, 구성원이 자원이 충분하다고 느끼면 심리적인 안정감을 느끼게 되고 이것이 창의적인 업무성과로 이어진다는 선행연구들과, 구성원이 상사와 좋은 사회적 교환관계를 가지고 있으면 그에 대한 의무감으로 보다 창의적인 성과를 낸다는 선행연구들이 다른 리더십이나 혹은 상사의 개인적인 특성과는 함께 연구되었다. 하지만, 임파워링 리더십과 구성원의 심리적 안정감 및 상사에 대한 의무감과의 정적인 상관관계를 다룬 연구는 없었다. 이에 이번 연구에서는 상사의 임파워링 리더십이 구성원에게 자원을 제공하고, 좋은 사회적 교환관계를 형성하기 때문에 구성원의 창의적 업무성과와 정적인 상관관계를 가지는데, 이 상관관계에 매개변수로 구성원의 심리적 안정감과 상사에 대한 의무감을 거친다는 심리적인 메커니즘에 대해 밝히고자 하였다. 또한 최근 임파워링 리더십이 항상 업무성과들과 정적인 상관을 지니지 않는다는 결과들이 도출되고 있는데, 이에 대한 해석을 기존 연구자들이 구성원의 개인적인 특성에 집중해 분석한 것과 달리, 이번 연구에서는 상사의 개인적인 특성에 대한 구성원의 인식이 정적, 혹은 부적 조절변수로 작용하여 항상 임파워링 리더십이 업무성과와 우상향 선형 관계를 가지지는 않는다는 것을 밝히고자 하였다. 특히, 이번 연구는 상사의 자기지향 및 타인지향이 가지고 있는 조절효과를 확인하고자 하였다. 이번 연구는 한국에 있는 여러 산업에 종사하는 리더와 구성원을 1대1로 대응시켜 데이터를 확보하였으며, 해당 기업에는 공기업과 사기업이 모두 포함되었다. 위계적 회귀분석 결과, 임파워링 리더십과 구성원의 심리적 안정감, 상사에 대한 의무감은 통계적으로 매우 유의미한 결과를 보였고, 위계적 회귀분석 결과 예상과는 다르게 임파워링 리더십과 구성원의 창의적 업무성과를 구성원의 상사에 대한 의무감과 구성원의 심리적 안정감이 매개한다는 가설은 확인되지 않았다. 이에 추가적으로 경로분석을 실시한 결과, 임파워링 리더십이 창의적 업무성과에 미치는 직접효과가 기대했던 수준보다 커서 매개효과가 통계적으로 유의미하지 않음을 확인하였다. 또한 조절효과 역시 예상과는 다르게 상사의 타인지향이 임파워링 리더십과 상사에 대한 의무감 사이에만 통계적으로 유의미한 조절효과를 보이는 것을 확인하였다. 본 연구가 제공하는 이론적 기여는 다음과 같다. 첫째로, 임파워링 리더십이 보여주는 업무성과와의 상반된 관계에 대해서 새로운 해석을 제공하였으며, 심리적 안정감 및 상사에 대한 의무감과의 정적인 상관을 제공함으로써 임파워링 리더십 연구에 기여하였다. 둘째로, 기존 연구들에서 연구의 직접적인 변수로 사용하지 않고 이론을 설명하는 데에 간접적으로 사용되던 의무감이라는 변수를 직접 측정하여 실증적으로 활용하였다. 셋째로, 자기지향과 타인지향의 변수의 관계를 확인하였고, 두 변수간의 관계에 대하여 설명하였던 경쟁 및 협력이론에 실증적 근거를 제시하였다. 마지막으로, 불성실한 응답을 제외하기 위한 방법론적 실천을 통하여, 활용한 데이터의 질을 높이기 위한 연구를 실증적으로 적용하였다는 것이다.In order to flexibly cope with dramatic external changes triggered by turbulent environments, accelerating world market competition, increasing task complexity and technology development, work organizations should accept the changing trend of organizational structures. They adapt to de-bureaucratized, flattered, and network-based organization structure to maximize work efficiency. Given such changes in the organizational structure, granting job autonomy, responsibilities, and power to subordinates become a key factor of settling in fast changing environment and maintaining sustainable competitive advantage. Empowering leadership enables organizations to keep up with fast changing environments by allocating power, authorizing responsibilities, and granting job autonomy to subordinates. And this empowerment eventually becomes a source of creativity. In the present study I demonstrated the psychological mechanism of empowering leadership on subordinates creative performance. Giving job resources and constructing good social exchange relationships have a positive relationship with subordinates creative performance. Also, according to conservation of resources theory and social exchange theory, many antecedent researches have already demonstrated that these traits of leadership have a positive effect on subordinates psychological safety and felt obligation to supervisor. Nonetheless, previous studies did not directly test the positive relationship between empowering leadership and subordinates psychological safety and felt obligation to supervisor. To overcome such a research gap, in the present study, I demonstrated the psychological mechanism between empowering leadership and subordinates creative performance which is mediated by subordinates psychological safety and felt obligation to supervisor using conservation of resources theory and social exchange theory. Also, recently some studies have focused on curvilinear and mixed results of the empowering leadership, and they mostly focused on subordinates individual traits. In this study, I focused on leaders individual traits and subordinates perception is another key of mixed results of empowering leadership. This study suggested that subordinates perception of their leaders other-orientation and self-concern could be a positive or negative moderator between empowering leadership and mediating variables. A sample of 161 leader and member dyads were collected from government-owned enterprises and privately-owned enterprises which are located in Republic of Korea in diverse industries. The hierarchical regression and path analysis results showed that empowering leadership has a positive relationship with subordinates psychological safety and felt obligation to supervisor. However, unexpectedly the positive relationship between empowering leadership and subordinates creative performance was not mediated by psychological safety or felt obligation to supervisor. To demonstrate these unexpected results, this study conducted path analysis. I made two path analysis models for comparison; study model and a modified study model which excludes the main effect between empowering leadership and subordinates creative performance. From this comparison, I found that direct effect between empowering leadership and creative performance is unexpectedly significant which leads to unexpected study results of mediating effects. Also, only subordinates perception of leaders other-orientation had a statistically marginal moderating effect between empowering leadership and felt obligation to supervisor. These findings contribute to organizational behavior literature in the following ways. First, this study expands our understanding of empowering leadership by suggesting its positive effect on subordinates psychological safety and felt obligation to supervisor. This study also suggests new perspectives to mixed result of empowering leadership by focusing on subordinates perception of leaders individual traits and attribution of leaders empowering leadership motive. Second, this study used felt obligation as a study variable and provided empirical data for felt obligation literature. Third, this study not only shows the moderating effect of leaders other-orientation between empowering leadership and felt obligation to supervisor, but also demonstrates that self-concern and other-orientation are not bi-polar concepts. Additionally, this study provided empirical basis for theory of cooperation and competition. Lastly, this study used bogus items and self-reporting method in order to identify careless responses and exclude them from study data. By using these methods of screening careless responses, this study used strict study data and contributed to the literature of data screening by providing empirical data. Despite some methodological limitations and unexpected study results, these findings suggest reconcile the inconsistent findings on empowering leadership by presenting new psychological mechanisms of psychological safety and felt obligation to supervisor and provide practical implications for leaders. I hope this study invigorates future research on empowering leadership and antecedent of psychological safety and felt obligation.Ⅰ. INTRODUCTION 1 Ⅱ. THEORETICAL BACKGROUND 5 1. Empowering Leadership 5 2. Psychological Safety 10 3. Felt Obligation 13 4. Self-concern and Other-orientation 15 Ⅲ. HYPOTHESIS DEVELOPMENT 18 1. The Main Effect between Empowering Leadership and Creativity 18 2. The Mediating Mechanism of Psychological Safety 18 3. The Mediating Mechanism of Felt Obligation 22 4. The Moderating Role of Self-concern and Other-orientation 26 Ⅳ. METHODS 32 1. Sample and Procedure 32 2. Measures 33 3. Analytical Strategy 35 Ⅴ. RESULTS 38 Ⅵ. POST-HOC STUDY 58 Ⅶ. DISCUSSION 64 1. Summary of Study Results 64 2. Theoretical and Practical Implications 66 3. Limitations and Directions for Future Research 70 Ⅷ. CONCLUSION 72 REFERENCES 73 APPENDIX 89 ABSTRACT (IN KOREAN) 93Maste

Reactions of Nickel(II) and Nickel(I) complexes of multiaza macrocyclic ligands

Thesis (master`s)--서울대학교 대학원 :화학과 유기화학전공,1996.Maste

The Weakening of Collective Identity in the Birth of Modern Individuals: Howellsian Understanding of Social Reality in The Rise of Silas Lapham

William Dean Howellss The Rise of Silas Lapham focuses on the meaning of collective identity breakdown in late nineteenth-century American society through the lens of the then rising individualism. As the traditional class identity lost much of its validity, people had to accommodate themselves to the different contexts in their own ways. The established common social values such as class and family ties were disintegrated while each individual had to survive in the turmoil of the burgeoning market economy. According to Howells, individuals can share the democratic experiences in the American soil which shape alternative common values to stick them together; the weakening collective identity is substituted for the individual identity coupled with the national identity. Such an Howellsian understanding of social reality is described in Silas Lapham

패혈증 비브리오균의 SmcR의 consensus sequence 규명 및 SmcR regulon과 독성관련 유전자의 유전체 수준에서의 분석

Thesis(doctors) --서울대학교 대학원 :농생명공학부, 2009.8.Docto

한국인 제2형 당뇨병 환자에서의 질병 진행 모형 개발

Dept. of Medical Science/박사Type 2 diabetes mellitus (T2DM) is a progressive disease. Decline in β-cell function, increase in insulin resistance with concomitant increase in fasting plasma glucose are the natural sequelae of T2DM. Although some pharmacotherapies for patients with type 2 diabetes mellitus have shown to slow the rate of progression or improve disease status, none of them has been proven to halt disease progression. Nevertheless, based on meta-analysis of existing data, it is hoped that more intensive treatment compared to standard glycemic control would significantly reduce coronary events without a parallel increase in mortality and morbidity. In such regards, disease progression of T2DM might be controlled by adopting proper treatment strategies. Pharmacometrics is a cutting-edge area of clinical pharmacology which is defined as the science that quantifies drug action, disease progression and patient information to aid efficient drug development, regulatory decision, and treatment in actual clinical practice. A disease model, represented by baseline disease status, natural disease history and drug (and placebo) response, describes the time course of disease progression, as measured by biomarkers or clinical outcomes, segregated from the drug response. The purpose of this study is to develop a disease progression model for Korean patients with T2DM and to apply the developed model as a supportive tool to designing an optimal treatment regimen in this clinical population using NONMEM.A total of 347 new or established patients who visited Severance hospital for the first time from 2006 to 2012 were retrospectively investigated after screening 888 patients. The patients were prescribed 0 to 3 kinds of oral hypoglycemic agents (OHAs) at first visit according to their disease status by endocrinology specialists. The primary endpoints measured were fasting plasma glucose (FPG, mmol/L) and glycated hemoglobin (HbA1c, %). We performed the analyses according to the intention-to-treat principle. Disease progression was modeled using the natural history and drug effect influencing the baseline (“offset”) or the progress rate (“slope”), or both. The constant, linear, simple Emax, sigmoid Emax and power models were evaluated to describe the treatment effect. The concept of effect compartment was applied to explain the delay in time course between pharmacokinetic steady state and pharmacodynamic steady state. The number of OHAs was incorporated into the structural model. Next, stepwise covariate model building was performed. The relationship between the structural parameters and the classes of the OHAs were investigated in this step. The final model was evaluated by the visual predictive check (VPC) for 1000 simulations. The median age of eligible patients (185 males, 162 females) was 61 years (19 – 85). Metformin was most frequently prescribed followed by sulfornylureas. The greater the number of OHA classes prescribed, the faster were the dropout rates. The number of patients without drug prescription was 19 and these patients were excluded from the population analysis because they were not suitable candidates for a placebo effect group. A total of 328 patients were prescribed 1 to 3 classes of OHAs. The number of OHAs positively correlated with the level of FPG or HbA1c acquired from initial laboratory tests. Linear models for offset effect and constant model for slope effect were incorporated into the final disease progression model for FPG and HbA1c. FPG and HbA1c increased naturally 0.197 mmol/L/year (3.55 mg/dL/year) and 0.181%/year, respectively. The amplitude of offset effect increased with the number of prescribed drugs in both FPG and Hb1Ac, though for HbA1c, there were little differences between 2 drugs and 3 drugs. The equilibration half-lives for offset effect were 14 days and 35 days for FPG and HbA1c, respectively. Therefore, it took around 55 to 69 days and 140 to 175 days for FPG and HbA1c, respectively to reach pharmacokinetic and pharmacodynamic equilibrium state. The disease progression rates of the Korean patients with type 2 diabetes mellitus who visited Severance hospital were similar to those of western patients, with rates for fasting plasma glucose and glycated hemoglobin 0.039 to 0.31 mmol/L and 0.07 to 0.24 %/L, respectively. Fasting plasma glucose decreased faster than glycated hemoglobin at the beginning of treatment. Treatment effect decreased inversely proportional to diabetes duration. The greater the number of prescribed drugs, the bigger was the offset effect. I will build disease progression model with greater utility after undertaking further studies.ope