협력 트랜잭셔널 워크플로우에서 데이타 일관성을 고려한 철회 종속성 감지 및 관리

변창우,박석 한국정보과학회 2003 정보과학회논문지 : 데이타베이스 Vol.27 No.4

데이타를 공유하며 협력적인 공동 작업을 필요로 하는 기업들간의 중요한 일을 수행하는 업무 연계와 같은 분야에서는 네트워크 인프라의 부족과 기업간의 정보 교환을 위한 표준의 부재, 서로 다른 업무들이 데이타베이스 관리 시스템에 접근하여 공유 데이타를 충돌 모드로 이용하는 경우의 데이타 일관성 유지 문제 등 많은 제약 요소에 의해 워크플로우를 적용하지 못하고 있다. 특히, 공유 데이타를 사용하고 있는 상황에서 발생될 수 있는 문제들에 대해서는 언급되어지지 않고 있다.본 논문에서는 업무 연계 관점에서 나타나는 공유 데이타를 사용하며 병행 수행되는 협력 트랜잭셔널 워크플로우들 사이에서 임의의 워크플로우와 다른 워크플로우들의 단계들 사이에서 발생될 수 있는 철회 종속성을 하나의 워크플로우에서의 암시적 철회 종속성, 협력 워크플로우 사이에서의 암시적 철회 종속성, 협력 워크플로우 사이에서의 명시적 철회 종속성 이렇게 세 가지로 분류하고, 데이타 일관성을 고려한 세 가지 철회 종속성을 워크플로우 스키마에 명시적으로 표현하는 자동 생성 알고리즘을 제안한다. 알고리즘을 실행하여 생성된 워크플로우 스키마는 데이타 공유와 관련하여 발생되는 런타임 철회 종속성을 데이타 일관성을 유지하며 런타임에 해결할 수 있도록 함으로써 워크플로우의 정확성을 향상시키게 된다. Workflow is not appropriately applied to coordinated execution of applications(steps) that comprise business process such as a collaborative series of tasks because of the lacks of network infra, standard of information exchange and data consistency management with conflict mode of shared data. Particularly we have not mentioned the problem which can be occurred by shared data with conflict mode.In this paper, to handle data consistency in the process of rollback for failure handling or recovery policy, we have classified rollback dependency into three types such as implicit rollback dependency in a transactional workflow, implicit rollback dependency in collaborative transactional workflows and explicit rollback dependency in collaborative transactional workflows. Also, we have proposed the rollback dependency compiler that determines above three types of rollback dependency. A workflow designer specifies the workflow schema and the resources accessed by the steps from a global database of resources. The rollback dependency compiler generates the enhanced workflow schema with the rollback dependency specification. The run-time system interprets this specification and executes the rollback policy with data consistency if failure of steps is occurred. After all, this paper can offer better correctness and performance than state-of-the-art WFMSs.

The Effect of Doping on Metal-Induced Lateral Crystallization Rate

변창우,이용우,박진현,석철균,김영수,주승기 대한금속·재료학회 2008 ELECTRONIC MATERIALS LETTERS Vol.4 No.2

The effect of dopants on the behavior of metal-induced lateral crystallization (MILC) growth was studied in this work. Two types of dopants (B2H6 and PH3) were doped over 50Å Nickel films deposited on amorphous silicon. It was found that the MILC growth rate of The MILC growth rate of B2H6- and PH3doped amorphous silicon (a-Si) thin film by ion mass doping (IMD) is slower than that of intrinsic a-Si. The decrease of growth rate was caused by the bonding of Si-P and the break down of the dangling bond between silicon and hydrogen during bonded ion mass doping. In addition, a phenomenon of growth stoppage at the boundary of the a-Si and ion mass doped range was observed. The rate of MILC growth decreased as dopant density increased

준고전적 보미안 궤적의 적용: 강한 레이저에 의한 일차원 원자모형의 이온화

변창우,이민호,최낙렬,김대성 한국물리학회 2014 새물리 Vol.64 No.1

To treat ionization of atoms in an intense laser field (ILF), we have to solve the time-dependent Schrodinger equation. Most existing traditional methods for doing that need computing resources that increase exponentially as the number of degrees of freedom of the system of interest grows. For this reason, there is no numerical quantum solution that can be compared with double-ionization of He in an ILF. Bohmian mechanics could allow the exponential scaling with system size to be circumvented by using trajectories, as in classical mechanics, for which the initial conditions are sampled using Monte Carlo techniques. We want to use semiclassical Bohmian mechanics, which doesn't need any pre-calculation of the wave function, in order to obtain solutions that we can compare with the experimental results for the ionization of multielectron atoms in an ILF. As a first stage, we survey the possibility of employing the semiclassical Bohmian method in a study of the above-threshold ionization in the 1-dimensional hydrogen model. 강한 레이저에 노출된 원자의 이온화 현상을 이론적으로 다루기 위해서는 시간의존 슈뢰딩거 방정식의 해를 구해야 하는데, 기존의 통상적인 방법으로는 계의 자유도가 늘어남에 따라 필요한 전산 자원이 지수적으로 늘어나게 되어, 지금까지도 800 nm 펨토초 레이저 펄스에 노출된 헬륨원자의 이-전자 이온화에 대한 실험 결과와 비교할 수 있는 양자역학적 수치 해가 알려져 있지 않다. 고전역학에서와 같이 궤적을 사용할 수 있는 방법을 사용하면, 초기조건을 몬테카를로 샘플링으로 취함으로써 자유도에 따른 전산 자원의 지수적 증가를 피할 수 있다. 우리는 파동함수에 대한 정보 없이 보미안 궤적을 수치적으로 구하는 방법의 하나로 알려진 준고전적 보미안 방법을 도입하여 강한 레이저에 노출된 다-전자 원자의 이온화 실험결과와 비교할 수 있는 수치 해를 구하고자 한다. 우선 그 첫 번째 단계로서 일차원 단-전자 원자 모형의 이온화를 다룸으로써 준고전적 보미안 방법의 적용 가능성을 검사한다.

Ga2O3초음파분무화학기상증착 공정에서 유동해석을 이용한 균일도 향상 연구

변창우,하주환,이학지,박소담,신석윤 한국반도체디스플레이기술학회 2022 반도체디스플레이기술학회지 Vol.21 No.4

Mist-CVD is known to have advantages of low cost and high productivity method since the precursor solution is misting with an ultrasonic generator and reacted on the substrate under vacuum-free conditions of atmospheric pressure. However, since the deposition distribution is not uniform, various efforts have been made to derive optimal conditions by changing the angle of the substrate and the position of the outlet to improve the result of the preceding study. Therefore, in this study, a deposition distribution uniformity model was derived through the shape and position of the substrate support and the conditions of inlet flow rate using the particle tracking method of computational fluid dynamics (CFD). The results of analysis were compared with the previous studies through experiment. It was confirmed that the rate of deposition area was improved from 38.7% to 100%, and the rate of deposition uniformity was 79.07% which was higher than the predicted result of simulation. Particle tracking method can reduce trial and error in experiments and can be considered as a reliable prediction method.

Effect of Ni Silicide Density on Electrical Performance of Silicide-Induced Crystallized Polycrystalline Silicon Thin-Film Transistors

변창우,A. Mallikarjuna Reddy,Se Wan Son,주승기 대한금속·재료학회 2012 ELECTRONIC MATERIALS LETTERS Vol.8 No.4

The electrical performance of low temperature polycrystalline silicon (LTPS) thin-film transistors (TFTs) fabricated by silicide-induced crystallization (SIC) is greatly affected by metal contamination such as Ni silicide. In this paper, the effect of Ni silicide density on the SIC poly-Si TFTs is investigated by in-situ Ni silicidation at room temperature, 100°C, 200°C, and 300°C, respectively. It was observed that grain size of fully crystallized polycrystalline silicon (poly-Si) decreased with the increase of in-situ silicidation temperature. This is due to an increase in the density of nucleation sites for crystallization. As a result, grain boundaries and interface trap-state densities were significantly increased and electrical properties such as subthreshold slope, on-state current and field effect mobility were drastically degraded.

보미안 궤적의 수치적 계산: 강한 레이저에 의한 일차원 원자모형의 이온화

변창우,이민호,최낙렬,김대성 한국물리학회 2015 새물리 Vol.65 No.1

Solutions to the time-dependent Schr¨odinger equations (TDSEs) are needed to treat ionization of many-electron atoms in intense laser fields. As the degrees of freedom of the system increase, the required computing resouces increase exponentially, precluding the possibility of numerical solutions. A quantum-mechanical treatment of the double ionization of the helium atom by femtosecond laser pulses still remains an inaccessible numerical problem. Bohmian mechanics has recently been considered as an alternative for solving the TDSEs. The generalized iterative finite difference method has been reported to have been conducted rather successfully among many methods using Bohmian mechanics. We examine the feasibility and the validity of the generalized iterative finite difference method as a numerical method for treating the ionization of the 1-dimensional hydrogen atom exposed to a strong laser pulse. 강한 레이져에 의한 다-전자 원자의 광이온화 현상의 이론적인 연구를 위해서는 시간의존 슈뢰딩거 방정식을 풀어야만 한다. 그러나 계의 자유도가 늘어날 수록 요구되는 전산 자원의 수요는 수치적인 해를 얻는 것을 불가능하게 만든다. 지금까지도 펨토초 레이져에 의한 원자의 이중 이온화에 대한 양자 계산은 기초적인 단계를 벗어나지 못하는 실정이다. 최근 보미안 역학은 양자 궤적을 이용하여 TDSE을 해결할 새로운 대안으로 고려되고 있다. 보미안 역학을 이용한 많은 방법 중에 일반화된 반복적 유한 차분법은 2차원 부조화 포텐셜 문제에 상당히 성공적으로 수행되었다. 강한 레이져에 노출된 일차원 수소원자 모형에 이 방법을 적용하여 레이져에 의한 원자의 이온화 현상에 보미안 역학의 사용 가능성을 조사하고자 한다.

문제해결기법 TRIZ의 ADRIGE 알고리즘을 이용한 초음파분무화학기상증착 장비 개발에 관한 연구

변창우,하주환,신석윤 한국반도체디스플레이기술학회 2023 반도체디스플레이기술학회지 Vol.22 No.2

This study the problem of deposition uniformity observed during Mist-CVD deposition experiments. The TRIZ's ADRIGE algorithm, a problem-solving technique, is utilized to systematically analyze the issue and propose solutions. Through problem and resource analysis, technical contradictions are identified regarding the precursor's volume and its path when it encounters the substrate. To resolve these contradictions, the concept of applying the principle of dimensional change to transform the precursor's three-dimensional path into a one-dimensional path is suggested. The chosen solution involves the design of an enhanced Mist-CVD system, which is evaluated for feasibility and analyzed using computational fluid dynamics. The analysis confirms that the deposition uniformity consistently follows a pattern and demonstrates an improvement in uniformity. The improved Mist-CVD equipment is validated through analysis, providing evidence of its feasibility and yielding satisfactory results.

High Performance Poly-Si Thin Film Transistors Fabricated by Self-Aligned Seed Induced Lateral Crystallization

변창우,손세완,이용우,윤승재,이상주,주승기 대한금속·재료학회 2011 ELECTRONIC MATERIALS LETTERS Vol.7 No.4

In this study, a low temperature polycrystalline silicon (LTPS) thin-film transistor (TFT) was fabricated by self-aligned silicide seed induced lateral crystallization (SA-SILC). In comparison with a self-aligned metal induced lateral crystallization (SA-MILC) TFT, the SA-SILC TFT showed better electrical properties. In particular,the leakage current was decreased by SA-SILC at high drain voltages. It was found that the Ni rich phase between the channel and drain junction region acted as trapping sites to generate leakage current by thermionic field emission. After applying the SA-SILC process, the p-channel polycrystalline silicon (poly-Si) TFT exhibited a mobility of 67 cm 2/V·s, a minimum leakage current of 2.6 × 10−11A at VD = −5 V,a subthreshold slope of 0.8 V/dec, and a maximum on/off ratio of 7.0 × 106, together resulting in a highperformance device that surpasses the conventional SA-MILC poly-Si TFT.

인공지능기법을 이용한 초음파분무화학기상증착의 유동해석 결과분석에 관한 연구

변창우,하주환,신석윤,김준영 한국반도체디스플레이기술학회 2023 반도체디스플레이기술학회지 Vol.22 No.1

This study focuses on the analysis of the results of computational fluid dynamics simulations of mist-chemical vapor deposition for the growth of an epitaxial wafer in power semiconductor technology using artificial intelligence techniques. The conventional approach of predicting the uniformity of the deposited layer using computational fluid dynamics and design of experimental takes considerable time. To overcome this, artificial intelligence method, which is widely used for optimization, automation, and prediction in various fields, was utilized to analyze the computational fluid dynamics simulation results. The computational fluid dynamics simulation results were analyzed using a supervised deep neural network model for regression analysis. The predicted results were evaluated quantitatively using Euclidean distance calculations. And the Bayesian optimization was used to derive the optimal condition, which results obtained through deep neural network training showed a discrepancy of approximately 4% when compared to the results obtained through computational fluid dynamics analysis. resulted in an increase of 146.2% compared to the previous computational fluid dynamics simulation results. These results are expected to have practical applications in various fields.

데이타 스트림 상에서 다중 연속 복수 조인 질의 처리 최적화 기법

변창우(Changwoo Byun),이헌주(Hunzu Lee),박석(Seog Park) 한국정보과학회 2008 정보과학회논문지 : 데이타베이스 Vol.35 No.1

센서 네트워크에 이용되는 데이타 스트림 관리 시스템에서는 한정적 정보들이 개별적으로 입력되기 때문에 종합적인 결과를 얻기 위해서는 상대적인 계산 비용이 높은 조인 연산자는 필연적으로 요구된다. 데이타 스트림은 잠재적으로 무한한 크기를 가지므로 조인 연산자는 슬라이딩 윈도우 제약사항을 가져야 함은 당연하다. 또한, 종합적인 결과를 얻기 위해 조인 연산자는 여러 입력을 취할 수 있어야 한다. 이를 가능하게 하는 것이 바로 슬라이딩 윈도우를 가지는 MJoin 연산자이다. 본 논문에서는 이러한 여러 MJoin 연산자가 시스템에 등록되어 있는 환경을 가정하고, 슬라이딩 윈도우를 가지는 MJoin의 특성을 반영하여 전역적으로 공유된 질의 처리 기법인 MMJoin 기법을 제안한다. MMJoin 기법은 첫째, 전역적으로 공유된 질의 실행 계획 수립 문제, 조인 연산 결과에 대한 윈도우 갱신 문제 및 라우팅 문제로 나누어 다룬다. 이러한 연구의 노력은 데이타 스트림 환경에서 효율적인 다중 질의 최적화 및 처리 기법의 기초연구로 활용될 수 있다. Join queries having heavy cost are necessary to Data Stream Management System in Sensor Network where plural short information is generated. It is reasonable that each join operator has a sliding-window constraint for preventing DISK I/O because the data stream represents the infinite size of data. In addition, the join operator should be able to take multiple inputs for overall results. It is possible for the MJoin operator with sliding-windows to do so. In this paper, we consider the data stream environment where multiple MJoin operators are registered and propose MMJoin which deals with issues of building and processing a globally shared query considering characteristics of the MJoin operator with sliding-windows. First, we propose a solution of building the global shared query execution plan. Second, we solve the problems of updating a window size and routing for a join result. Our study can be utilized as a fundamental research for an optimization technique for multiple continuous joins in the data stream environment.