• Journal of Welding and Joining
• /
• 제17권1호
• /
• pp.124-132
• /
• 1999

Thermal fatigue strength of the solder joints is the most critical issue for TSOP(Thin Small Outline Package) because the leads of this package are extremely short and thermal deformation cannot be absorbed by the deflection of the lead. And the TSOP body can be subject to early fatigue failures in thermal cycle environments. This paper was discussed distribution of thermal stresses at near the joint between silicon chip and die pad and investigated their reliability of solder joints of TSOP with 42 alloy clad lead frame on printed circuit board through FEM and 3 different thermal cycling tests. It has been found that the stress concentration around the encapsulated edge structure for internal crack between the silicon chip and Cu alloy die pad. And using 42 alloy clad, The reliability of TSOP body was improved. In case of using 42 alloy clad die pad(t=0.03mm). $$\sigma$_{VMmax}$ is 69Mpa. It is showed that 15% improvement of the strength in the TSOP body in comparison with using Cu alloy die pad $($\sigma$_{VMmax}$=81MPa). In solder joint of TSOP, the maximum equivalent plastic strain and Von Mises stress concentrate on the heel of solder fillet and crack was initiated in it's region and propagated through the interface between lead and solder. Finally, the modified Manson-Coffin equation and relationship of the ratio of $N_{f}$ to nest(η) and cumulative fracture probability(f) with respect to the deviations of the 50% fracture probability life $(N_{f 50%})$ were achieved.

• 한국농공학회논문집
• /
• 제59권3호
• /
• pp.29-39
• /
• 2017

In this study, the GPM (Global Precipitation Mission) IMERG (Integrated Multi-satellitE retrievals for GPM) rainfall data was verified and evaluated using ground AWS (Automated Weather Station) and radar in order to investigate the availability of GPM IMERG rainfall data. The SPI (Standardized Precipitation Index) was calculated based on the GPM IMERG data and also compared with the results obtained from the ground observation data for the Hoengseong Dam and Yongdam Dam areas. For the radar data, 1.5 km CAPPI rainfall data with a resolution of 10 km and 30 minutes was generated by applying the Z-R relationship ($Z=200R^{1.6}$) and used for accuracy verification. In order to calculate the SPI, PERSIANN_CDR and TRMM 3B42 were used for the period prior to the GPM IMERG data availability range. As a result of latency verification, it was confirmed that the performance is relatively higher than that of the early run mode in the late run mode. The GPM IMERG rainfall data has a high accuracy for 20 mm/h or more rainfall as a result of the comparison with the ground rainfall data. The analysis of the time scale of the SPI based on GPM IMERG and changes in normal annual precipitation adequately showed the effect of short term rainfall cases on local drought relief. In addition, the correlation coefficient and the determination coefficient were 0.83, 0.914, 0.689 and 0.835, respectively, between the SPI based GPM IMERG and the ground observation data. Therefore, it can be used as a predictive factor through the time series prediction model. We confirmed the hydrological utilization and the possibility of real time drought monitoring using SPI based on GPM IMERG rainfall, even though results presented in this study were limited to some rainfall cases.

• 한국수정란이식학회지
• /
• 제24권1호
• /
• pp.65-69
• /
• 2009

The aim of the present study was to investigate the cleavage pattern, its developmental ability and apoptosis of porcine embryo in vitro. Morphology data on a total of 919 embryos were analyzed retrospectively. Forty-eight hours after insemination, embryos were classified into five groups based on the cleavage state as follows; 1 cell, 2 cell, 4 cell, 5 to 8 cell and fragmentation. These groups were cultured another 120 hours and then evaluated for blastocyst formation. Blastocyst formation rates were significantly higher in 4 cell (42.5%) and 5 to 8 cell (48.6%) cleaving groups than in other groups (p<0.05). On the other hand, 2 cell and fragmentation groups produced 4.9% and 3,9% blastocysts, respectively. And we could verify that in the event of 2 cell block and fragmentation of embryo. To analyze the apoptotic frequency in preimplantation development of porcine IVF embryos, all cells of each blastocyst were performed by TUNEL assay. There were no significantly differences in the total cell numbers of embryos and apoptotic cell rate in blastocysts among the each classified groups. Data suggest that 4 cell and 5 to 8 cell cleaving embryos at 48 hour after insemination have high developmental competence, and may be an useful parameter to predict the development of preimplantation embryos and to study using preimplanation embryonic research.

• Nuclear Engineering and Technology
• /
• 제48권5호
• /
• pp.1184-1191
• /
• 2016

This paper introduces the development of a transient monitoring system to detect the early stage of a transient, to identify the type of the transient scenario, and to inform an operator with the remaining time to turbine trip when there is no operator's relevant control. This study focused on the transients originating from a secondary system in nuclear power plants (NPPs), because the secondary system was recognized to be a more dominant factor to make unplanned turbine-generator trips which can ultimately result in reactor trips. In order to make the proposed methodology practical forward, all the transient scenarios registered in a simulator of a 1,000 MWe pressurized water reactor were archived in the transient pattern database. The transient patterns show plant behavior until turbine-generator trip when there is no operator's intervention. Meanwhile, the operating data periodically captured from a plant computer is compared with an individual transient pattern in the database and a highly matched section among the transient patterns enables isolation of the type of transient and prediction of the expected remaining time to trip. The transient pattern database consists of hundreds of variables, so it is difficult to speedily compare patterns and to draw a conclusion in a timely manner. The transient pattern database and the operating data are, therefore, converted into a smaller dimension using the principal component analysis (PCA). This paper describes the process of constructing the transient pattern database, dealing with principal components, and optimizing similarity measures.

• 디지털융복합연구
• /
• 제14권11호
• /
• pp.233-240
• /
• 2016

정보시스템 개발 프로젝트는 다양한 리스크 요소로 인하여 많은 비용이 발생하는 구조를 가지고 있다. 일반적으로 정보시스템 소프트웨어 프로젝트가 납기 내에 성공적으로 이루어질 확률은 매우 낮아 프로젝트 실패를 막는 주요한 요인인 정형화된 비용에 대한 예측이 필요하다. 그러나 대부분의 프로젝트 규모 산정 시 산정 기준의 객관성이 부족하며, 프로젝트 수행 중 베이스라인의 관리가 제대로 이루어지지 않고 있는 실정이다. 이에 본 논문에서는 정보시스템 개발 프로젝트 초기에 현장에서 실용적이지 못한 기법의 한계를 극복하고자 방법론 기반으로 개발에 소요되는 공수를 산정하는 모델을 제안한다. 이러한 융복합적인 제안 모델을 통하여 정보시스템 개발 사업에서 소요되는 공수와 비용을 추정하는데 간단하게 활용할 수 있는 도구가 될 것으로 기대된다.

• Nuclear Engineering and Technology
• /
• 제47권1호
• /
• pp.74-84
• /
• 2015

If a transient occurs in a nuclear power plant (NPP), operators will try to protect the NPP by estimating the kind of abnormality and mitigating it based on recommended procedures. Similarly, operators take actions based on severe accident management guidelines when there is the possibility of a severe accident occurrence in an NPP. In any such situation, information about the occurrence time of severe accident-related events can be very important to operators to set up severe accident management strategies. Therefore, support systems that can quickly provide this kind of information will be very useful when operators try to manage severe accidents. In this research, the occurrence times of several events that could happen during a severe accident were predicted using support vector machines with short time variations of plant status variables inputs. For the preliminary step, the break location and size of a loss of coolant accident (LOCA) were identified. Training and testing data sets were obtained using the MAAP5 code. The results show that the proposed algorithm can correctly classify the break location of the LOCA and can estimate the break size of the LOCA very accurately. In addition, the occurrence times of severe accident major events were predicted under various severe accident paths, with reasonable error. With these results, it is expected that it will be possible to apply the proposed algorithm to real NPPs because the algorithm uses only the early phase data after the reactor SCRAM, which can be obtained accurately for accident simulations.

• 대한조선학회논문집
• /
• 제53권5호
• /
• pp.371-379
• /
• 2016

In the ship design process, ship motion and propulsion performance in sea waves became very important issues. Especially, prediction of ship propulsion performance during real operation is an important challenge to ship owners for economic operation in terms of fuel consumption and route-time evaluation. Therefore, it should be considered in the early design stages of the ship. It is thought that the averaged value and fluctuation of effective inflow velocity to the propeller have a great effect on the propulsion performance in waves. However, even for the nominal velocity distribution, very few results have been presented due to some technical difficulties in experiments. In this study, flow measurements near the propeller plane using a stereo PIV system were performed. Phase-averaged flow fields on the propeller plane of a KVLCC2 model ship in waves were measured in the towing tank by using the stereo PIV system and a phase synchronizer with heave motion. The experiment was carried out at fully loaded condition with making surge, heave and pitch motions free at a forward speed corresponding to Fr=0.142 (Re=2.55×106) in various head waves and calm water condition. The phase averaged nominal velocity fields obtained from the measurements are discussed with respect to effects of wave orbital velocity and ship motion. The low velocity region is affected by pressure gradient and ship motion.

• 콘크리트학회지
• /
• 제9권2호
• /
• pp.121-132
• /
• 1997

콘크리트의 열해석은 콘크리트 초기온도, 환경조건 및 시멘트의 수화 등에 의해 특징지워진다. 이러한 상호관계를 모두 고려한 프로그램을 만들어서, 콘크리트재료의 열특성과 환경조건을 감안한 콘크리트 구조물의 온도해석을 하였다. 시멘트 수화의 특성으로는 활성화에너지, 단위열량, 수화열이 있으며 이러한 인자들에 의해 콘크리트의 내부열 발생이 영향을 받는다. 본 연구에서는 활성화에너지와 수화열을 상대강도-등가재령모델에 의해 구했으며, 단위열량은 등온열량측정법에 의해 실험적으로 구하였다. 또한 콘크리트 구조물의 온도분포를 실험적으로 구하여 수치해석모델과 비교하였다. 먼저 위에서 제시된 모든 조건들에 대한 parametric 해석을 실시하여 프로그램의 신뢰성을 확보하였다. 그리고 원주형시편을 만들어서 온도분포 및 변화를 측정하여 수치해석에 의해 예측된 온도분포와 비교하였다.

• 천문학회보
• /
• 제39권1호
• /
• pp.47.2-47.2
• /
• 2014

Several studies have reported the presence of sodium excess objects having neutral atomic absorption lines at $5895{\AA}$ (NaD) and $8190{\AA}$ that are deeper than expected based on stellar population models that match the stellar continuum. The origin of these lines is therefore hotly debated. van Dokkum & Conroy proposed that low-mass stars (0.3M) are more prevalent in massive early-type galaxies, which may lead to a strong NaI 8190 line strength. It is necessary to test this prediction, however, against other prominent optical line indices such as NaD, Mgb, and Fe5270, which can be measured with a significantly higher signal-to-noise ratio than NaI 8190. We identified a new sample of roughly one thousand NaD excess objects (NEOs; ~8% of galaxies in the sample) based on NaD line strength in the redshift range 0.00$H{\beta}$ line strengths and significant emission lines, which are indicative of the presence of young stellar populations. This result implies that the presence of the interstellar medium and/or dust contributes to the increase in NaD line strengths observed for these galaxies.

• Journal of Communications and Networks
• /
• 제16권4호
• /
• pp.407-414
• /
• 2014

The Internet is a highly distributed and complex system consisting of billion devices and has become the field of various kinds of conflicts during the last two decades. As a matter of fact, various actors utilise the Internet for illicit purposes, such as for performing distributed denial of service attacks (DDoS) and for spreading various types of aggressive malware. Despite the fact that numerous services provide information regarding the threat level of the Internet, they are mostly based on information acquired by their sensors or on offline statistical sampling of various security applications (antivirus software, intrusion detection systems, etc.). This paper introduces proactive threat observatory system (PROTOS), an open-source early warning system that does not require a commercial license and is capable of estimating the threat level across the Internet. The proposed system utilises both a global and a local approach, and is thus able to determine whether a specific host is under an imminent threat, as well as to provide an estimation of the malicious activity across the Internet. Apart from these obvious advantages, PROTOS supports a large-scale installation and can be extended even further to improve the effectiveness by incorporating prediction and forecasting techniques.