• Nuclear Engineering and Technology
• /
• 제10권2호
• /
• pp.65-72
• /
• 1978

원자로 가동시, 정상상태에서 벗어나 갑작스럽게 출력이 바뀔 때 발생하는 응력의 집중과 핵 분열시 발생하는 요오드의 부식에 의해서 생기는 피복물질의 응력 부식파괴현상을 이해하기 위하여, 이번 실험에서는 지르칼로이-4(Zicaloy-4)관을 사용하여 요오드응력부식 실험을 원자로 안의 상태에 가깝도록 30$0^{\circ}C$의 상태아래서 행하였다. 요오드 농도에 따라서 지르칼로이-4, 관(Tube)의 응력부식에 한 파괴시간을 구했고, 응력부식을 일으킬 수 있는 임계요오드 농도 및 임계접선방향의 응력을 구하였다. 요오드에 의한 응력부식이 화학석인 반응이라기 보다는 기계적인 반응성격을 갖기 때문에 응력부식을 파괴 역학적인 관점에서 설명하고자 응력과 파괴시간을 함수관계로 다음과 같이 표시해 보았다. log t$_{F}$ =5.5- (3/2) log$_{c}$-4log$\sigma$ t$_{F}$ : 파괴시간(") c : 요오드농도(mg/㎤) $\sigma$ : 응력 ($10^4$psi).

• 대한기계학회논문집B
• /
• 제29권3호
• /
• pp.376-383
• /
• 2005

In the paper we investigate characteristics of a transitional behavior from a premixed flame to a triple flame in a lifted flame according to the change of equivalence ratio. In previous study, we showed that the stabilized laminar lifted flame regime is categorized by regimes of premixed flame, triple flame and critical flame. A gas-chromatograph is used to measure concentration field, a smoke-wire system is used to measure streak line, and a PIV system is used to measure velocity field in lifted flame. In the visualization experiment of smoke wire, the flow divergence and redirection reappeared in premixed flame as well as triple flame. Thus we cannot express the flame front of lifted flame has a behavior of triple flame with only flow divergence and redirection. In PIV measurement, flow velocity for those three flames has minimum value at the tip of flame front. To differentiate triple flame and premixed flame, $\Phi$ value of partially premixed fraction is employed. The partially premixed fraction $\Phi$ was constant in premixed flame. In critical flame small gradient appears over the whole regime. In triple flame, typical diffusion flame shape is obtained as parabolic distribution type due to diffusion flame trailing.

• The Korean Journal of Physiology and Pharmacology
• /
• 제20권4호
• /
• pp.367-378
• /
• 2016

Recently, it was reported that the role of mitochondria-reactive oxygen species (ROS) generating pathway in cisplatin-induced apoptosis is remarkable. Since a variety of molecules are involved in the pathway, a comprehensive approach to delineate the biological interactions of the molecules is required. However, quantitative modeling of the mitochondria-ROS generating pathway based on experiment and systemic analysis using the model have not been attempted so far. Thus, we conducted experiments to measure the concentration changes of critical molecules associated with mitochondrial apoptosis in both human mesothelioma H2052 and their ${\rho}^0$ cells lacking mitochondrial DNA (mtDNA). Based on the experiments, a novel mathematical model that can represent the essential dynamics of the mitochondrial apoptotic pathway induced by cisplatin was developed. The kinetic parameter values of the mathematical model were estimated from the experimental data. Then, we have investigated the dynamical properties of this model and predicted the apoptosis levels for various concentrations of cisplatin beyond the range of experiments. From parametric perturbation analysis, we further found that apoptosis will reach its saturation level beyond a certain critical cisplatin concentration.

• 한국해양공학회지
• /
• 제25권5호
• /
• pp.47-51
• /
• 2011

This paper analyzes the fatigue-life of welded joints using the notch stress approach. In the notch stress approach, the notch effects are usually approximated by introducing weld-bead parameters for the local detailed weld joints. The actual bead shape is complex and 3-dimensional. It may also greatly influence the fatigue strength. In this study, the welded shape was modeled using a 3D-scanner. The critical distance method was adopted in the evaluation of the fatigue effective notch stress for the weldments. Fatigue life tests were performed to verify the present method of fatigue life estimation for two types of welded plates with longitudinal attachments. The estimated results of the present methods were applied to the results of the experiment. The results of the analysis showed that the scatter of fatigue-life for the experimental data expressed in the nominal stress was significantly reduced by applying the effective fatigue stress of the present study.

• Journal of Mechanical Science and Technology
• /
• 제18권7호
• /
• pp.1222-1235
• /
• 2004

This study examines the influence of geometry on the internal flow and macroscopic behavior of the spray in Diesel nozzles. For this investigation, two bi-orifice nozzles were employed: one cylindrical and one conical. The first step is to use a non-destructive characterization method which is based on the production of silicone moulds so that the precise internal geometry of the two nozzles can be measured. At this stage the nozzles have been characterized dimensionally and therefore the internal flow can be studied using CFD calculations. The results gained from this experiment make it possible also to ascertain the critical cavitation conditions. Once the critical cavitation conditions have been identified, the macroscopic parameters of the spray can be studied in both cavitating and non-cavitating conditions using a test rig pressurized with nitrogen and with the help of a image acquisition system and image processing software. Consequently, research can be carried out to determine the influence that cavitation has on macroscopic spray behavior. From the point of view of the spray macroscopic behavior, the main conclusion of the paper is that cavitation leads to an increment of the spray cone angle. On the other hand, from the point of view of the internal flow, the hole outlet velocity increases when cavitation appears. This phenomenon can be explained by the reduction in the cross section of the liquid phase in the outlet section of the hole.

• 한국통신학회논문지
• /
• 제10권3호
• /
• pp.123-129
• /
• 1985

본 연구는 100kHz의 대역폭에서 SNR이 0dB 정도인 미소신호의 존재유무를 판단하기 위한 임계치 결정방법에 대하여 기술한 것이다. 검출방법은 니만-피어슨등의 전통적인 방법에 비해서 미소신호에 적합한 LOD방법을 적용한 것이다. 검출의 대상신호는 데이터전송이나 모르스부호 전소에 사용되는 OOK변조신호이고, 잡음은 전송로에서 일반적으로 존재하는 라프라시안형의 비가우시안형을 대상으로 하였다. 실험결과, 오판확률을 임의의 값으로 고정시키고, 한 점의 임계를 취한 경우에서의 검출확률과 두 점의 구간임계점을 상호, 비교한 결과 후자의 검출방법이 현저히 향상됨을 확인하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제49권11호
• /
• pp.589-595
• /
• 2000

In this papre, AC losses of Bi-2223 tapes with different twist pitch of superconducting core were fabricated, measured and analyzed. These samples produced by a powder-in-tube method are multi-filamentary tape with Ag matrix. Also, it's produced by non-twist and different twist pitch(8, 10, 13, 30, 50, 70 mn). The critical current measurement was carried out under the environment in Liquid nitrogen and in zero field by 4-probe method. And the AC loss measurement was carried out under the environment of applied time-varying transport current by transport method. From experiment, the critical current is larger non-twist than twisted filament. And, the AC loss by Norris equation is higher non-twisted tape than 13mm twisted tape. Also, it is confirmed that of AC loss of tape having non-twist pitch larger than those having differnet twist pitch.

• 한국가시화정보학회:학술대회논문집
• /
• 한국가시화정보학회 2006년도 추계학술대회 논문집
• /
• pp.125-130
• /
• 2006

The characteristics of boiling heat transfer and critical heat flux (CHF) behavior of nano-fluids were studied by using various sized silver and alumina nanoparticles. The diameter of nanoparticles was from 2 nm to 250 nm for silver and from 20nm to 40nm for alumina. Pool boiling characteristics and CHF enhancement of nano-fluids with different sized nanoparticles were compared with those of pure water and each nano-fluids. The experiment was performed at atmospheric pressure and the temperature of the pool was maintained constantly by using a flat immersed heater. The concentration of nano-fluids was uniform in all experiments as 0.01g/liter. The results showed that the measured boiling curves were shifted to the right. It demonstrated that the occurrence of nucleate boiling regime in nano-fluids retarded, compared with that of pure water. Also, in nano-fluids, the boiling curves showed that CHF of nano-fluids is significantly enhanced and represented the effect of particle size on boiling characteristics.

• Nuclear Engineering and Technology
• /
• 제52권5호
• /
• pp.1079-1092
• /
• 2020

A parametric study of several parameters relevant to design safety on the spent nuclear fuel (SNF) rod response under a drop accident is presented. In the view of the complexity of interactions between the independent safety-related parameters, a factorial design of experiment is employed as an efficient method to investigate the main effects and the interactions between them. A detailed single full-length fuel rod is used with consideration of post-irradiated fuel conditions under horizontal and vertical free-drops onto an unyielding surface using finite-element analysis. Critical drop heights and critical g-loads that yield the threshold plastic strain in the cladding are numerically estimated to evaluate the fuel rod structural resistance to impact load. The combinatory effects of four uncertain parameters (pellet-cladding interfacial bonding, material properties, spacer grid stiffness, rod internal pressure) and the interactions between them on the fuel rod response are investigated. The principal finding of this research showed that the effects of above-mentioned parameters on the load-carrying capacity of fuel rod are significantly different. This study could help to prioritize the importance of data in managing and studying the structural integrity of the SNF.

• 한국추진공학회지
• /
• 제23권2호
• /
• pp.21-26
• /
• 2019

신속하게 감압되는 환경에 노출되면 연소중인 고체추진제는 소화가 일어난다. 연소되는 중인 고체추진제를 소화하는데 필요한 압력 감소율인 임계감압률을 찾는 실험이 진행되었다. 이를 위해 감압 시점, 감압 속도, 초기 압력, 최종 압력을 조절할 수 있는 감압연소기를 설계 및 제작하였다. 이 실험의 결과는 특정 AP/HTPB 복합고체추진제 조성에서 소화와 비소화 사이의 경계를 결정하는데 사용되었다. 실험 결과 초기 압력과 최종 압력이 소화를 위한 임계감압률에 큰 영향을 미치는 것으로 나타났다.