• Title/Summary/Keyword: critical parameters

Search Result 1,959, Processing Time 0.03 seconds

Development of Deterioration Prediction Model and Reliability Model for the Cyclic Freeze-Thaw of Concrete Structures (콘크리트구조물의 반복적 동결융해에 대한 수치 해석적 열화 예측 및 신뢰성 모델 개발)

  • Cho, Tae-Jun;Kim, Lee-Hyeon;Cho, Hyo-Nam
    • Journal of the Korea Concrete Institute
    • /
    • v.20 no.1
    • /
    • pp.13-22
    • /
    • 2008
  • The initiation and growth processes of cyclic ice body in porous systems are affected by the thermo-physical and mass transport properties, as well as gradients of temperature and chemical potentials. Furthermore, the diffusivity of deicing chemicals shows significantly higher value under cyclic freeze-thaw conditions. Consequently, the disintegration of concrete structures is aggravated at marine environments, higher altitudes, and northern areas. However, the properties of cyclic freeze-thaw with crack growth and the deterioration by the accumulated damages are hard to identify in tests. In order to predict the accumulated damages by cyclic freeze-thaw, a regression analysis by the response surface method (RSM) is used. The important parameters for cyclic freeze-thawdeterioration of concrete structures, such as water to cement ratio, entrained air pores, and the number of cycles of freezing and thawing, are used to compose the limit state function. The regression equation fitted to the important deterioration criteria, such as accumulated plastic deformation, relative dynamic modulus, or equivalent plastic deformations, were used as the probabilistic evaluations of performance for the degraded structural resistance. The predicted results of relative dynamic modulus and residual strains after 300 cycles of freeze-thaw show very good agreements with the experimental results. The RSM result can be used to predict the probability of occurrence for designer specified critical values. Therefore, it is possible to evaluate the life cycle management of concrete structures considering the accumulated damages due to the cyclic freeze-thaw using the proposed prediction method.

Design and Implementation of a Transparent Security Infrastructure using Filter and Transformer (필터와 트랜스포머를 이용한 투명한 보안기반의 설계 및 구현)

  • Kim, Yong-Min;Lee, Do-Heon;Noh, Bong-Nam;Choi, Rak-Man;Ine, So-Ran
    • The Transactions of the Korea Information Processing Society
    • /
    • v.5 no.4
    • /
    • pp.975-983
    • /
    • 1998
  • In these days, information communication systems are based on both open distributed computing technologies and object-oriented techniques like inheritance, encapsulation and object reuse to support various system configuration and application. As information systems are interconnected through unsecure networks, the need for the secure information exchange is more critical than before. In this paper, we have designed and implemented a transparent CORBA-basce Security infrastructure with authentication, security context association, access control and security information management to support a secure applications in distributed object environment. SESAME Ver. 4 was adopted as an external security service to manage user privilege attributes and to distribute keys for data encryption, decryption and integrity. Using filter and transformer with an interface to Object Request Broker, it provides a transparent security service to applications. The filter objects are special classes that allow additional parameters to be inserted into messages before they are sent and removed just after they are received. The transformer objects are special classes that allow direct access to the byte stream of every messages for encryption and decryption before it is sent and just after it is received. This study is to implement the access control interceptor(ACI) and the secure invocation interceptor(SII) of secure ORB defined in CORBA using filter and transformer.

  • PDF

Development of Computational Evaluation Method for Fatigue Crack Growth Rate based on Viscoplastic-Damage Model (점소성-손상모델 기반 피로균열 진전속도 전산 평가법 개발)

  • Kim, Seul-Kee;Kim, Jeong-Hyeon;Lee, Chi-Seung;Kim, Myung-Hyun;Lee, Jae-Myung
    • Journal of the Computational Structural Engineering Institute of Korea
    • /
    • v.28 no.1
    • /
    • pp.1-8
    • /
    • 2015
  • In this paper, computational evaluation method for fatigue crack growth rate(FCGR) based on material viscoplastic-damage model is proposed. Viscoplastic-damage model expressing material constitutive behavior of 7% nickel steel is introduced and is implemented into commercial finite element analysis(FEA) code, ABAQUS, as a user defined material subroutine(UMAT) for application in the FEA environments. Verification of developed UMAT and material parameters of material model are carried out by uniaxial tensile test simulations of 7% nickel steel. Moreover, jump-in-cycles procedure and rearrangement of critical damage are employed and also implemented to the ABAQUS UMAT for fatigue damage analysis. Typical FCGR test results such as relationship between crack length and number of cycles and relationship between da/dN and ${\Delta}K$ could be obtained from FCGR test simulation using developed UMAT and these results are compared with experimental results in order to verify of proposed computational method.

Evaluation of Dynamic Lane Allocation Method at Climbing Lane Section (통행속도에 기반한 오르막차로 동적 운영방안 평가)

  • Ko, Han-Geom;Choi, Yoon-Hyuk;Oh, Young-Tae;Kang, Jeong-Gyu
    • Journal of Korean Society of Transportation
    • /
    • v.30 no.1
    • /
    • pp.59-72
    • /
    • 2012
  • In aspects of traffic operation, a climbing lane may cause traffic congestion if the volume of traffic (v/c) grows and the ratio of heavy vehicle increases. Conversely, it would be effective, if the climbing lane is dynamically operated according to changes in traffic flow. However, there are no guideline to effectively control this climbing lane in aspects of traffic operation. In this study, we examine the necessity of flexible traffic operation criteria and its process for dynamic traffic management and also establish and analyze the effect of flexible traffic operation criteria in accordance with traffic properties using an example of climbing lane. We selected the operation criteria (critical travel speed), which decides whether to operate or close the climbing lane when the average travel speed of climbing lane is 50km/h based on VISSM (microscopic traffic simulation) analysis of Nakdong junction towards Masan with the volume of traffic (v/c), ratio of heavy vehicle as the traffic operation parameters. Based on the simulation result in accordance with the volume of traffic by the operation mode of climbing lane, the analysis on the effect of dynamic traffic management of climbing lane showed that the dynamic traffic management provides more convenience compare to the operation and close of climbing lane. Thereby, we proved that the dynamic traffic management of climbing lane is more effective.

A Study on the Design Parameters of a Gasket and Innercase of a Refrigerator to Reduce Dew Generation on the Outer Surface (표면의 이슬 맺힘 저감을 위한 냉장고 가스켓 및 냉동냉장실 내벽 구조개선에 관한 연구)

  • Kang, Seok-Hoon;Kim, Seong-Jin;Kim, Ju-Hwan;Min, June-Kee;Sohn, Chang-Min;Park, Sang-Hu
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.36 no.4
    • /
    • pp.457-463
    • /
    • 2012
  • Current refrigerators are designed to have thin doors and walls to facilitate user convenience and increase inner storage space. However, the thin doors and walls gives rise to the problem of dew generation on the outer surface of a refrigerator due to a large critical temperature difference between the outer wall and the room air; So far, an electric heater is commonly used for making the dew to evaporate; in this case, the heater inevitably requires additional electrical power. We propose a new approach to reduce the dew generation in a refrigerator by redesigning the gasket and varying the thickness of the inner case of the refrigerator. The results of simulations performed in this study indicate that the surface temperature in the region where dew was generated was increased by approximately $0.39{\sim}3.07^{\circ}C$ without the use of a heater.

Mixed-mode simulation of transient characteristics of 4H-SiC DMOSFETs - Impact off the interface changes (Mixde-mode simulation을 이용한 4H-SiC DMOSFETs의 계면상태에서 포획된 전하에 따른 transient 특성 분석)

  • Kang, Min-Seok;Choe, Chang-Yong;Bang, Wook;Kim, Sang-Chul;Kim, Nam-Kyun;Koo, Sang-Mo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • 2009.11a
    • /
    • pp.55-55
    • /
    • 2009
  • Silicon Carbide (SiC) is a material with a wide bandgap (3.26eV), a high critical electric field (~2.3MV/cm), a and a high bulk electron mobility (${\sim}900cm^2/Vs$). These electronic properties allow high breakdown voltage, high frequency, and high temperature operation compared to Silicon devices. Although various SiC DMOSFET structures have been reported so far for optimizing performances. the effect of channel dimension on the switching performance of SiC DMOSFETs has not been extensively examined. In this paper, we report the effect of the interface states ($Q_s$) on the transient characteristics of SiC DMOSFETs. The key design parameters for SiC DMOSFETs have been optimized and a physics-based two-dimensional (2-D) mixed device and circuit simulator by Silvaco Inc. has been used to understand the relationship with the switching characteristics. To investigate transient characteristic of the device, mixed-mode simulation has been performed, where the solution of the basic transport equations for the 2-D device structures is directly embedded into the solution procedure for the circuit equations. The result is a low-loss transient characteristic at low $Q_s$. Based on the simulation results, the DMOSFETs exhibit the turn-on time of 10ns at short channel and 9ns at without the interface charges. By reducing $SiO_2/SiC$ interface charge, power losses and switching time also decreases, primarily due to the lowered channel mobilities. As high density interface states can result in increased carrier trapping, or recombination centers or scattering sites. Therefore, the quality of $SiO_2/SiC$ interfaces is important for both static and transient properties of SiC MOSFET devices.

  • PDF

Design of a CMOS Dual-Modulus Prescaler Using New High-Speed Low-Power TSPC D-Flip Flops (새로운 고속 저전력 TSPC D-플립플롭을 사용한 CMOS Dual-Modulus 프리스케일러 설계)

  • Oh, Kun-Chang;Lee, Jae-Kyong;Kang, Ki-Sub;Park, Jong-Tae;Yu, Chong-Gun
    • Journal of IKEEE
    • /
    • v.9 no.2 s.17
    • /
    • pp.152-160
    • /
    • 2005
  • A prescaler is an essential building block for PLL-based frequency synthesizers and must satisfy high-speed and low-power characteristics. The design of D-flip flips used in the prescaler implementation is thus critical. Conventional TSPC D-flip flops suffer from glitches, unbalanced propagation delay, and unnecessary charge/discharge at internal nodes in precharge phase, which results in increased power consumption. In this paper a new dynamic D-flip flop is proposed to overcome these problems. Glitches are minimized using discharge suppression scheme, speed is improved by making balanced propagation delay, and low power consumption is achieved by removing unnecessary discharge. The proposed D-flip flop is employed in designing a 128/129 dual-modulus prescaler using $0.18{\mu}m$ CMOS process parameters. The designed prescaler operates up to 5GHz while conventional one can operate up to 4.5GHz under same conditions. It consumes 0.394mW at 4GHz that is a 34% improved result compared with conventional one.

  • PDF

Genetic Variations in the HIF1A Gene Modulate Response to Adjuvant Chemotherapy after Surgery in Patients with Colorectal Cancer

  • Zhang, Yi;Wang, Peng;Zhou, Xing-Chun;Bao, Guo-Qiang;Lyu, Zhuo-Ming;Liu, Xiao-Nan;Wan, Shao-Gui;He, Xian-Li;Huang, Qi-Chao
    • Asian Pacific Journal of Cancer Prevention
    • /
    • v.15 no.11
    • /
    • pp.4637-4642
    • /
    • 2014
  • Background: Hypoxia-inducible factor $1{\alpha}$ (HIF-$1{\alpha}$) plays an important role in regulating cell survival and angiogenesis, which are critical for tumor growth and metastasis. Genetic variations of HIF1A have been shown to influence the susceptibility to many kinds of human tumors. Increased expression of HIF-$1{\alpha}$ has also been demonstrated to be involved in tumor progression. However, the prognostic value of single nucleotide polymorphisms (SNPs) inthe HIF1A gene remains to be determined in most cancer types, including colorectal cancer (CRC). In this study, we sought to investigate the predictive role of HIF1A SNPs in prognosis of CRC patients and efficacy of chemotherapy. Materials and Methods: We genotyped two functional SNPs in HIF1A gene using the Sequenom iPLEX genotyping system and then assessed their associations with clinicopathological parameters and clinical outcomes of 697 CRC patients receiving radical surgery using Cox logistic regression model and Kaplan Meier curves. Results: Generally, no significant association was found between these 2 SNPs and clinical outcomes of CRC. In stratified analysis of subgroup without adjuvant chemotherapy, patients carrying CT/TT genotypes of rs2057482 exhibited a borderline significant association with better overall survival when compared with those carrying CC genotype [Hazard ratio (HR), 0.47; 95% confidence interval (95% CI): 0.29-0.76; P < 0.01]. Moreover, significant protective effects on CRC outcomes conferred by adjuvant chemotherapy were exclusively observed in patients carrying CC genotype of rs2057482 and in those carrying AC/CC genotype of rs2301113. Conclusions: Genetic variations in HIF1A gene may modulate the efficacy of adjuvant chemotherapy after surgery in CRC patients.

Art of Dislocation, Exile, and Diaspora: Korean Artists in New York in the 1960s and 1970s (1960-70년대 뉴욕의 한국작가: 이주, 망명, 디아스포라의 미술)

  • Yang, Eunhee
    • The Journal of Art Theory & Practice
    • /
    • no.16
    • /
    • pp.107-137
    • /
    • 2013
  • This paper examines a number of Korean artists-Whanki Kim, Po Kim, Byungki Kim, Lim Choong-Sup, Min Byung-Ok and etc-working in New York in the 1960s and 1970s, focusing on their motivations to head for the U.S. and their life and activity in the newly-emerged city of international art. The thesis was conceived based upon the fact that New York has been one of the major venues for Korean artists in which to live, study, travel and stay after the Korean War. Moreover, the United States, since 1945, has had a tremendous influence upon Korea politically, socially, economically, and, above all, culturally. This study is divided into three major sections. The first one attends to the reasons that these artists moved out of Korea while including in this discussion, the long-standing yearning of the Korean intelligentsia to experience more modernized cultures, and American postwar cultural policies that stimulated them to envision life beyond their national parameters, in a country heavily entrenched in Cold War ideology. The second part examines these artists' pursuit of abstraction in New York where it was already losing its avant-garde status as opposed to the style's cutting edge cache in Korea. While their turn to abstraction was outdated from New York's critical perspective, it was seen to be de rigueur for Koreans that had developed through phases from Art Informel in the 1960s to Dansaekhwa (monochromatic paintings) in the 1970s. The third part focuses on the artists' struggle while caught between a dualistic framework such as Korea/U.S, East/West, center/margin, traditional/modern, and abstraction/figuration. Despite such dichotomic frames, they identified abstract art as the epitome of pure, absolute art, which revealed their beliefs inherited from western modernism during the colonial period before 1910-1945. In fact, their reality as immigrants in America put them in a diasporic space where they oscillated between the fixed, essentialist Korean identity and the floating, transforming identity as international artists in New York or Korean-American artists. Thus their abstract and semi-abstract art reflect the in-between identity from the diasporic space while demonstrating their yearning for a land of political freedom, intellectual fulfillment and the continuity of modern art's legacy imposed upon them over the course of Korea's tumultuous history in the twentieth century and making the artists as precursor of transnational, transcultural art of the global age in the twenty-first century.

  • PDF

Forecasting the Precipitation of the Next Day Using Deep Learning (딥러닝 기법을 이용한 내일강수 예측)

  • Ha, Ji-Hun;Lee, Yong Hee;Kim, Yong-Hyuk
    • Journal of the Korean Institute of Intelligent Systems
    • /
    • v.26 no.2
    • /
    • pp.93-98
    • /
    • 2016
  • For accurate precipitation forecasts the choice of weather factors and prediction method is very important. Recently, machine learning has been widely used for forecasting precipitation, and artificial neural network, one of machine learning techniques, showed good performance. In this paper, we suggest a new method for forecasting precipitation using DBN, one of deep learning techniques. DBN has an advantage that initial weights are set by unsupervised learning, so this compensates for the defects of artificial neural networks. We used past precipitation, temperature, and the parameters of the sun and moon's motion as features for forecasting precipitation. The dataset consists of observation data which had been measured for 40 years from AWS in Seoul. Experiments were based on 8-fold cross validation. As a result of estimation, we got probabilities of test dataset, so threshold was used for the decision of precipitation. CSI and Bias were used for indicating the precision of precipitation. Our experimental results showed that DBN performed better than MLP.