메탄/공기 층류 부분예혼합화염의 상세 라디칼(OH*, CH* 그리고 C₂*) 정보와 배기매출물에 관한 실험적 연구

정용기,오정석,전충환,장영준,Jeong Yong Ki,Oh Jeong Seog,Jeon Chung Hwan,Chang Young June 대한기계학회 2005 大韓機械學會論文集B Vol.29 No.2

An experimental study was performed to investigate the effects of partially premixing, varying the equivalence ratios from $0.79{\sim}{\infty}$, on NOx emissions and chemiluminescence of excited $OH^{\ast},\;CH^{ast}\;C_2^{\ast}$ radicals in laminar partially premixed flames. the signal from the electronically excited state of $OH^{\ast},\;CH^{ast}\;C_2^{\ast}$ was detected through a band pass filter with a photo multiplier tube, which are processed to the intensity ratio ($C_2^{\ast}/CH^{\ast},\;C_2^{\ast}/OH^{\ast},\;and\;CH^{\ast}/OH^{\ast}$) to reveal the correlation with local equivalence ratio. And measurements of NOx emission were made to investigate the relationship between visible flame appearance, chemiluminescence, and EINOX. The results demonstrated that (1) the flames at ${\phi}<1.59$ exhibited classical double flame structure, at ${\phi}>4.76$, the flames exhibited diffusion flame structure, and the intermediate flames at $1.59<{\phi}<4.76$ was a merged flame, (2) the $OH^{\ast}$ peak was located inside the $CH^{\ast}\;and\;C_2^{\ast}$ radical for all measured conditions and the emission intensity ratio of $C_2^{\ast}/CH^{\ast}\;and\;C_2^{\ast}/OH^{\ast}$ were identified as good marker for local equivalence ratio over a range of ${\phi}=0.79{\sim}1.2\;and\;CH^{\ast}/OH^{\ast}\;is\;0.79<{\phi}<1.9$. However, it was difficult to predict the equivalence ratio in partially premixed flames using this system for ${\phi}>2.38$, (3) the minimum NOX emission index (EINOx) is obtained for a equivalence ratio of 3.19 in the intermediate flames.

메탄 공기 층류 부분 예혼합화염에서 예혼합 정도에 따른 화염구조와 질소산화물의 배출에 미치는 영향에 관한 연구

오정석(Jeong Seog Oh),정용기(Yong Ki Jeong),전층환(Chung Hwan Jeon),장영준(Young June Chang) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11

It is shown that the effect of variable parameters on flame structures and NOx emissions in the laminar<br/> partially premixed methane-air flames with a co-axial Bunsen burner. Objectives of this paper is to<br/> understand the effects of flow variables on NOx emissions and the flame structure with OH<br/> chemiluminescence, including reconstructed image by abel inversion processing at each conditions. A fuel<br/> flowrate of 200 [cc/min] was fixed and the amount of air was varied from 400 to 1200 [cc/min]. The<br/> experimental variables were equivalence ratio( ), fuel split percentage( ) and inner tube recess(x/D). Flow<br/> conditions were ranged from 1.36~4.76(equivalence ratio), 50~100(fuel split percentage) and 0~20(inner<br/> tube recess). NOx analyzer and ICCD camera with a OH filter were used as a main experimental<br/> apparatus. In addition, Abel inversion, which is a kind of tomography and valuable to estimate a<br/> two-dimensional structure of co-axial flames from cubical information, was employed for combustion<br/> diagnostics. Results from this study indicate that the main effects depend on equivalence ratio and next<br/> sigma, x/D for NOx production and OH formation. Throughout Abel inversion, we could affirm the<br/> maximum position and the tendency of OH radical intensity by variants at five axial heights above the<br/> burner exit.

데이타베이스 워크로드 분석 : 실험적 연구

오정석,이상호,Oh, Jeong-Seok,Lee, Sang-Ho 한국정보처리학회 2004 정보처리학회논문지D Vol.11 No.4

데이타베이스 시스템을 효율적으로 사용하기 위해 데이타베이스 관리자는 데이타베이스 시스템의 성능 특징들을 알아야 한다 데이터베이스 시스템에서 자원 사용은 워크로드에 따라 다르게 나타난다. 본 논문의 목적은 상이할 워크로드에서 데이타베이스 튜닝에 도움이 될 수 있도록 데이타베이스 시스템의 성능 특징 분석하고 식별하는 것이다. 이를 위해, OLTP 환경을 나타내는 TPC-C 워크로드와 웹기반의 전자상거래 환경을 나타내는 TPC-W워크로드에서 14개의 성능 지표에 의해 결정되는 자원 사용 형태를 분석하고 4개(데이타 버퍼, 개인 메모리, I/O 프로세스, 공유 메모리)의 자원 할당 변경에 따른 자원 사용 형태의 변화를 분석한다. 분석에 대한 결과로서 14개 중 8개의 성능 지표는 워크로드에서 성능차이를 보이고, 데이타 버퍼 자원의 변경은 데이타베이스 시스템에 영향을 준다. 본 논문의 결과는 데이타베이스 시스템 자동 튜닝의 기초 자료로서 사용될 수 있다. Database administrators should be aware of performance characteristics of database systems in order to manage database system effectively. The usages of system resources in database systems could be quite different under database workloads. The objective of this paper is to identify and analyze performance characteristics of database systems in different workloads, which could help database tuners tune database systems Under the TPC-C and TPC-W workloads, which represent typical workloads of online transaction processing and electronic commerce respectively, we investigated usage types of resource that are determined by fourteen performance indicator, and are behaved in response to changes of four tuning parameters (data buffer, private memory, I/O process, shared memory). Eight out of the fourteen performance indicators cleary show the performance differences under the workloads. Changes of data buffer parameter give a influences to database system. The tuning parameter that affects the system performance significantly is the database buffer size in the both workloads.

데이터베이스 워크로드에서의 자원 식별

오정석,이상호,Oh Jeong-Seok,Lee Sang-Ho 한국정보처리학회 2006 정보처리학회논문지D Vol.13 No.2

Database workloads may show different resource usages for database applications. Database administrators can enhance the DBMS performances through resource management that reflects workload characteristics. We provide a method that can identify tunable resources from analyzing the relationship between performance indicators and resources. First, we select which performance indicators increase or decrease by expanding resources using a correlation coefficient and a significance level test. Next, we identify resources that can affect the DBMS Performances by using increasing or decreasing performance indicators. We evaluated our method in the TPC-C and TPC-W environments. 데이터베이스 응용분야에 따라 데이터베이스 워크로드는 서로 다른 자원 사용 형태를 보인다. 데이터베이스 관리자는 워크로드 특성을 반영하는 자원 관리를 통하여 시스템 성능을 향상시킬 수 있다. 본 논문은 성능지표와 자원간의 관계를 분석하여 데이터베이스 시스템 성능에 영향을 주는 자원을 선별하는 방법을 제시한다. 첫째, 본 방법은 피어슨 상관계수와 유의도 검정을 적용하여 데이터베이스 시스템 자원 확장에 대해 감소되거나 증가되는 성능지표를 선별한다. 둘째, 감소/증가 관계를 갖는 성능지표를 이용하여 데이터베이스 시스템에 성능에 영향을 주는 자원을 선별한다. 실험은 TPC-C 및 TPC-W 환경에서 본 방법을 수행하였으며, 제안된 자원 선별 방법에 대한 검증 시험을 수행하였다.

스텔라이트 합금 용사 코팅의 피로 강도에 미치는 후열처리의 영향

오정석,이창규,Oh Jeong Seong,Komotori Jun,Rhee Chang Kyu 한국분말야금학회 2005 한국분말재료학회지 (KPMI) Vol.12 No.2

The effect of post-heat treatment on the coating characteristics and the fatigue strength of the gas flame thermally sprayed Stellite alloy coatings on $0.35\%$ carbon steel were investigated. The fatigue fracture surfaces of the heat treated samples were observed using SEM (Scanning Electron Microscopy). For as-sprayed samples, there was considerable scattering in the fatigue life due to the presence of the pores in the coating. After the post-heat treatment to improve the microstructural characteristics of the coating layer, the fatigue strength of the specimens was greatly improved, increasing with increasing the coating thickness. For the specimens with the 0.3mm and 0.5mm thick coating, the fatigue cracks originated in the substrate region just below the interface. On the contrary, for the specimens with the 1.0mm thick coating, they nucleated at the pore within the coating, and the fatigue strength was 2.6 times higher than that of the substrate due to the high fatigue resistance of the coating.

전기 폭발법에 의해 제조된 Cu-Ni 나노 분말의 윤활성 향상

오정석,박중학,김흥회,이창규,Oh J.S.,Park J.H.,Kim W.W.,Rhee C.K. 한국분말야금학회 2004 한국분말재료학회지 (KPMI) Vol.11 No.5

Nanoscale Cu-Ni alloy nanopowders have been produced by a pulsed wire evaporation method in an inert gas. The effect of Cu-Ni alloy nanopowders as additives to motor oil on the tribological properties was studied at room temperature. The worn surfaces were characterized by Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS). Cu-Ni alloy nanopowders as additives lowered coefficient of friction and wear rate. It was found that a copper containing layer on the worn surface was formed, and deposited layers of the metal cladding acted as lubricant on the worn surface, reducing the friction coefficient. It was clearly demonstrated that Cu-Ni alloy nanopowders as additives are able to restore the worn surface and to preserve the friction surfaces from wear.

유전자 조작 , 균주분리 페놀 분해 Rhodococcus sp . DGUM 2011 의 분리 및 특성

오정석,한영환 ( Jung Suk Oh,Yeong Hwan Han ) 한국미생물생명공학회 1997 한국미생물·생명공학회지 Vol.25 No.5

지적분야 종사자의 자율성 정도가 조직성과에 미치는 영향 - 리더십의 매개효과를 중심으로 -

오정석,Oh, Jung-Seok 한국국토정보공사 공간정보연구원 2014 지적과 국토정보 Vol.44 No.2

본 연구의 목적은 지적분야 종사자의 자율성 정도, 리더십, 조직성과 간에 영향관계를 알아보는 데 있다. 설문조사는 대한지적공사 직원을 대상으로 실시하였고 SPSS 20.0과 AMOS19.0을 이용하여 구조방정식 모형을 검증하였다. 분석을 통한 결과 및 시사점은 다음과 같다. 첫째, 자율성이 조직성과(직무만족과 조직몰입)에 직접적인 효과는 없었으며, 단지 간접적으로 영향을 미치는 결과가 도출되었다. 기존 연구는 자율성이 직무만족과 조직몰입에 긍정적 영향이 있었다. 하지만 본 연구는 자율성이 높다고 해서 조직성과가 높아지는 것은 아닌 것으로 나타났다. 아마도 이 결과는 분석대상이 공공부문이기 때문일 것이다. 둘째, 자율성과 조직성과간 관계에서 리더십은 매개효과가 있었다. 리더십은 지적분야 종사자가 직무에 만족하고 조직에 몰입할 수 있는 실천적인 측면에서 매우 중요한 의미를 가진다고 할 수 있다. 즉, 업무의 특성과 공기업이라는 특수성으로 자율성이 잘 보장되지 않는 상황을 리더십을 통해 보완할 수 있기 때문이다. 셋째, 지적분야 관리자의 리더십 역량, 직무만족, 조직몰입을 강화할 수 있는 교육 및 프로그램의 개발이 필요하다. The purpose of this study is to find out the influence on Organizational Performance of Autonomy in Cadastral Employees. The survey was conducted around the branch Korea Cadastral Survey Corporation. Using SPSS 20.0 and Amos 19.0, Structural Equating model was verified. The results of the analysis and the proposal is as follows. First, autonomy not directly but indirectly affected job satisfaction and organizational commitment. This had a positive impact on job satisfaction and organizational commitment, autonomy existing research. But it was not the organization's performance by increasing the autonomy to higher study. Perhaps it is analyzed the results of the public sector. Second, the relationship between autonomy and organizational performance in leadership had a mediating effect. And increase organizational performance factors, leadership has a very important meaning. Public good is not guaranteed autonomy. Therefore, it is possible to compensate through leadership. Third, cadastral field manager leadership competencies, it is necessary to develop a training program to enhance the organizational commitment and job satisfaction.

음파가진이 부상된 수소 난류 확산화염에 미치는 영향

오정석(Jeongseog Oh),허필원(Pilwon Heo),윤영빈(Youngbin Yoon) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

The effects of acoustic excitation on the reduction in nitric oxidant (NOx) emission were experimentally investigated in non-premixed lifted hydrogen jet flames with coaxial air. The purpose of this work was to find an effective method to reduce NOx emission, to analyse the acoustic forcing effect on the flow field, the reaction zone, and NOx emission, and to study NOx reduction mechanisms. For the analysis of the flow field, a PIV method was used that incorporated two Nd-YAG lasers and a CCD camera. The reaction zone was visualized by taking OH<SUP>*</SUP> chemiluminescence images with a 307.1±5 ㎚ narrow band pass filter and an ICCD camera. A flow condition was carefully selected at uF=200 ㎧ and uA=16 ㎧, which was sustainable for the acoustic excitation in a lifted flame region. The frequency was swept from 150 to 1000 ㎐ in 5 ㎐ steps. And then NOx emissions were detected with a NOx sensor and recorded in a DAQ system. From the measurements of the flow field, the reaction zone, and NOx emission, we concluded that NOx emission was reduced and minimized at a resonance frequency. The vortex that was generated by acoustic forcing promoted air entrainment and enhanced fuel-air premixing. This premixing effect resulted in a lower flame temperature, and thus, a lower NOx emission.

이중동축 메탄/공기 층류 부분 예혼합화염에서의 화염구조와 자발광 배출 특성 안쪽관 연료주입의 영향

오정석(Jeong Seog Oh),정용기(Yong Ki Jeong),전충환(Chung Hwan Jeon),장영준(Young June Chang) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11

In this study, the effect of central fuel injection on a coaxial laminar CH₄/air flame was experimented at the defined premixing condition(φ=1.90, σ=50/75/100%, x/D=10). The partial premixing parameter are the equivalence ratio that total fuel is fixed at 200cc/min, the fuel split degree which means the percentage of fuel entering the outer tube to the total amount, and the mixing distance indicating the nonreactant mixture's homogeneity between inner tube top and burner exit. The object is to investigate the flame structure and chemiluminescence characteristics of laminar partial premixed flame as changing mixing parameters. The radical signal was acquired from ICCD camera and PMT. Each intensity was compared with Abel inverted value for measuring the effect of background light on the peak signal location and the intensity at central preheat zone. The results show that the peak location of each radical was broaden as the fuel split degree increasing because the mixing quality was enhanced. and OH* is a good indicator for flame front between reaction and preheat zone. At last C₂* has the same tendency with CH* but a thinner reaction zone than CH* due to a rapid decay on the burned gas side.