• Title/Summary/Keyword: Load support performance

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Evaluation of the performance for the reformed lattice girders (개량형 격자지보재의 성능 평가)

  • Kim, Hak-Joon;Bae, Gyu-Jin;Kim, Dong-Gyu
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.15 no.3
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    • pp.201-214
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    • 2013
  • Lattice girders are widely used as a substitute for H-steel ribs at domestic tunnels. However, lattice girders have a weak point in terms of the support capacity compare to H-steel ribs because of the lower stiffness and the weakness of the welded parts. To improve the weakness of the lattice girder, reformed lattice girders are developed in Korea by adding one more spider and having flat welded surface. Laboratory tests and field measurements were performed for the original and the reformed lattice girders to evaluate the performance of the reformed lattice girders. According to the laboratory compression test, reformed lattice girders have 16% higher load bearing capacity than that of original lattice girders. Reformed lattice girders are more stable than original lattice girders because reformed lattice girders tend to bend less according to the field measurements.

DGNSS-CP Performance Comparison of Each Observation Matrix Calculation Method (관측 행렬 산출 기법 별 DGNSS-CP 성능 비교)

  • Shin, Dong-hyun;Lim, Cheol-soon;Seok, Hyo-jeong;Yoon, Dong-hwan;Park, Byungwoon
    • Journal of Advanced Navigation Technology
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    • v.20 no.5
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    • pp.433-439
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    • 2016
  • Several low-cost global navigation satellite system (GNSS) receivers do not support general range-domain correction, and DGNSS-CP (differential GNSS) method had been suggested to solve this problem. It improves its position accuracy by projecting range-domain corrections to the position-domain and then differentiating the stand-alone position by the projected correction. To project the range-domain correction, line-of-sight vectors from the receiver to each satellite should be calculated. The line-of-sight vectors can be obtained from GNSS broadcast ephemeris data or satellite direction information, and this paper shows positioning performance for the two methods. Stand-alone positioning result provided from Septentrio PolaRx4 Pro receiver was used to show the difference. The satellite direction information can reduce the computing load for the DGNSS-CP by 1/15, even though its root mean square(RMS) of position error is bigger than that of ephemeris data by 0.1m.

A numerical study on the seismic behavior of a composite shear wall

  • Naseri, Reza;Behfarnia, Kiachehr
    • Computers and Concrete
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    • v.22 no.3
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    • pp.279-289
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    • 2018
  • Shear walls are one of the important structural elements for bearing loads imposed on buildings due to winds and earthquakes. Composite shear walls with high lateral resistance, and high energy dissipation capacity are considered as a lateral load system in such buildings. In this paper, a composite shear wall consisting of steel faceplates, infill concrete and tie bars which tied steel faceplates together, and concrete filled steel tubular (CFST) as boundary columns, was modeled numerically. Test results were compared with the existing experimental results in order to validate the proposed numerical model. Then, the effects of some parameters on the behavior of the composite shear wall were studied; so, the diameter and spacing of tie bars, thickness and compressive strength of infill concrete, thickness of steel faceplates, and the effect of strengthening the bottom region of the wall were considered. The seismic behavior of the modeled composite shear wall was evaluated in terms of stiffness, ductility, lateral strength, and energy dissipation capacity. The results of the study showed that the diameter of tie bars had a trivial effect on the performance of the composite shear wall, but increasing the tie bars spacing decreased ductility. Studying the effect of infill concrete thickness, concrete compressive strength, and thickness of steel faceplates also showed that the main role of infill concrete was to prevent buckling of steel faceplates. Also, by strengthening the bottom region of the wall, as long as the strengthened part did not provide a support performance for the upper part, the behavior of the composite shear wall was improved; otherwise, ductility of the wall could be reduced severely.

Design and Comparative Performance Analysis of Fully Distributed Mobility Management Scheme on PMIPv6 (PMIPv6 기반의 완전 분산형 이동성 관리 기법의 설계 및 성능 비교 분석)

  • Lee, Han-Bin;Lee, Jong Hyup
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2016.05a
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    • pp.220-223
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    • 2016
  • Explosive growth of smartphone-based mobile nodes has increased exponentially the mobile data traffic on the Internet. To reduce the traffic load on the network and to support the seamless mobility of the mobile nodes, the IETF and 3GPP have standardized a number of mobility management mechanisms. More recently, they are making an effort to find some schemes to distribute the networking systems that involve in the mobility management in order to assure the scalability and the reliability of the network. In IETF, DMM concept for the distributed mobility management on the Internet is being discussed. Specifically, the DMM can be classified into the partially distributed management and fully distributed management. In this paper, we propose a fully distributed mobility management scheme (FuDMM) on PMIPv6-based network by applying the extended NDP. We also present the performance of FuDMM using the comparative analysis with the existing ones.

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A mechanical model of vehicle-slab track coupled system with differential subgrade settlement

  • Guo, Yu;Zhai, Wanming;Sun, Yu
    • Structural Engineering and Mechanics
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    • v.66 no.1
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    • pp.15-25
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    • 2018
  • Post-construction subgrade settlement especially differential settlement, has become a key issue in construction and operation of non-ballasted track on high-speed railway soil subgrade, which may also affect the dynamic performance of passing trains. To estimate the effect of differential subgrade settlement on the mechanical behaviors of the vehicle-slab track system, a detailed model considering nonlinear subgrade support and initial track state due to track self-weight is developed. Accordingly, analysis aiming at a typical high-speed vehicle coupled with a deteriorated slab track owing to differential subgrade settlement is carried out, in terms of two aspects: (i) determination of an initial mapping relationship between subgrade settlement and track deflections as well as contact state between track and subgrade based on a semi-analytical method; (ii) simulation of dynamic performance of the coupled system by employing a time integration approach. The investigation indicates that subgrade settlement results in additional track irregularity, and locally, the contact between the concrete track and the soil subgrade is prone to failure. Moreover, wheel-rail interaction is significantly exacerbated by the track degradation and abnormal responses occur as a result of the unsupported areas. Distributions of interlaminar contact forces in track system vary dramatically due to the combined effect of track deterioration and dynamic load. These may not only intensify the dynamic responses of the coupled system, but also have impacts on the long-term behavior of the track components.

Mechanisms of the Autonomic Nervous System to Stress Produced by Mental Task in a Noisy Environment (소음상황에서 인지적 과제에 의해 유발된 스트레스에 대한 자율신경반응의 기제)

  • Sohn, Jin-Hun;Estate M. Sokhadze;Lee, Kyung-Hwa;Kim, Yeon-Kyu;Park, Sangsup
    • Proceedings of the Korean Society for Emotion and Sensibility Conference
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    • 1999.11a
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    • pp.216-221
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    • 1999
  • A mental task combined with noise background is an effective model of laboratory stress for study of psychophysiology of the autonomic nervous system (ANS). The intensity of the background noise significantly affects both a subjective evaluation of experienced stress level during test and the physiological responses associated with mental load in noisy environments. Providing tests of similar difficulties we manipulated the background noise intensity as a main factor influencing a psychophysiological outcome and the analyzed reactivity along withe the noise intensity dimension. The goal of this study was to identify the patterns of ANS responses and the relevant subjective stress scores during performance of word recognition tasks on the background of white noise (WN) of the different intensities (55, 70 and 85 dB). Subjects were 27 college students (19-24 years old). BIOPAC, Grass Neurodata System and AcqKnowlwdge 3.5 software were used to record ECG, PPG, SCL, skin temperature, and respiration. Experimental manipulations were effective in producing subjective and physiological responses usually associated with stress. The results suggested that the following potential autonomic mechanisms might be involved in the mediation of the observed physiological responses: A sympathetic activation with parasympathetic withdrawal during mild 55 and 70dB noise (featured by similar profiles) and simultaneous activation of sympathetic and parasympathetic systems during intense 85dB WN. The parasympathetic activation in this case might be a compensatory effect directed to prevent sympathetic domination and to maintain optimal arousal state for the successful performance on mental stress task. It should be mentioned that obtained results partially support Gellhorn's (1960; 1970) "tuning phenomenon" as a possible mechanism underlying stress response.

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Evaluation of Machining Characteristics and Performance Analysis of Air-Lubricated Dynamic Bearing (공기동압베어링의 성능 해석 및 가공특성 평가)

  • Baek, Seung-Yub;Kim, Kwang-Lae
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.12 no.12
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    • pp.5412-5419
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    • 2011
  • The need is growing for high-speed spindle because various equipment are becoming more precise, miniaturization and high speed with the development of industries. Air-lubricated dynamic bearings are widely used in the optical lithographic manufacturing of wafers to realize nearly zero friction for the motion of the stage. Air-lubricated dynamic bearing can be used in high-speed, high-precision spindle system and hard disk drive(HDD) because of its advantages such as low frictional loss, low heat generation, averaging effect leading better running accuracy. In the paper, numerical analysis is undertaken to calculate the performance of air-lubricated dynamic bearing with herringbone groove. The static performances of herringbone groove bearings which can be used to support the thrust load are calculated. Electrochemical micro machining($EC{\mu}M$) which is non-contact ultra precision machining method has been developed to fabricate the air-lubricated dynamic bearing and optimum parameters which are inter electrode gap size, concentration of electrolyte, machining time are simulated using numerical analysis program.

A Performance Analysis and Evaluation of Congestion Avoidance Algorithm for ABR service over ATM Networks (ATM망에서 ABR 서비스를 위한 혼잡회피 알고리즘의 성능 분석 및 평가)

  • 하창승;조익성
    • Journal of the Korea Society of Computer and Information
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    • v.7 no.3
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    • pp.80-91
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    • 2002
  • A general goal of the AT%(Asynchronous Transfer Mode) network is to support connect across various network. On ATM networks, ABR services are provided using the remained ban after allocation CBR and VBR traffic. Realtime services such as transmitting audio or video data may be provided using CBR ado VBR which have a constrained transmission delay, but in these cases, the communications bandwidth may be wasted. In this paper a simulation has been performed to compare and evaluate the performance between the ERICA(Explicit Rate Indicate Avoidance) and EPRCA(Enhanced Proportional Rate Control Algorithm) switches which use Explicit Rate switch algorithm for ABR switch. The variation of the ACR at the source end system, the queue length, the utilization rate of the link bandwidth and the share fairness at the transient and steady states are used as the evaluation criteria for the simulation. As a result of simulation, ERICA algorithm switch was ten times long compared to ERPCA switch to achieve assigned fair share. so EPRCA switch is superior to ERICA about load response. For Fair share and stability, ERICA switch is excellent to EPRCA switch.

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Science Teachers' Difficulties and Solutions of Free Semester Science Assessment (자유학기제 과학과 평가에서 과학 교사가 겪는 어려움과 해결방안)

  • Kim, Yura;Choi, Aeran
    • Journal of the Korean Chemical Society
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    • v.63 no.3
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    • pp.166-182
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    • 2019
  • This study examined teachers' difficulties that they encountered free semester science assessment and their problem solutions. Fifteen science teachers who had experiences of free semester teaching and assessment were selected by convenience sampling in this study. The participant teachers mentioned difficulties of accurate scoring in student self/peer assessment and suggested solutions of providing studetns with detailed assessment criteria and opportunities to practice assessment. The participant teachers mentioned a lack of objective assessment criteria for affective domain and suggested solutions of providing criteria prior to assessment and developing assessment framework. The participant teachers mentioned a lack of assessment tools and references for perforamnce assesement. The participant teachers mentioned difficulties of a large teacherstudent ratio for providng feedbacks to students and suggested solutions of decreasing teacher-student ratio and teaching load. The participant teachers mentioned difficulties of identifying student characteristics for assessment reporting and suggested solutions of decreaing teacher work load. The participant teachers mentioned a lack of teacher understanding of process based assessment and inactive attitude to performance assessment and suggested solutions of professional learning community and improving teacher perceptions on performance assessment. The participant teachers mentioned difficulties of a large teacher-student ratio and a lack of time for implementing assessment methods that they learned from professional development programs. With both teacher self-efforts and systematic support, these problems would be solved and success of free semester assessment would be achieved.

Study of Small Craft Resistance under Different Loading Conditions using Model Test and Numerical Simulations (모형시험과 수치해석을 이용한 하중조건 변화에 따른 소형선박의 저항성능 변화에 관한 연구)

  • Jun-Taek, Lim;Michael;Nam-Kyun, Im;Kwang-Cheol, Seo
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.29 no.6
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    • pp.672-680
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    • 2023
  • Weight is a critical factor in the ship design process given that it has a substantial impact on the hydrodynamic performance of ships. Typically, ships are optimally designed for specific conditions with a fixed draft and displacement. However, in reality, weight and draft can vary within a certain range owing to operational activities, such as fuel consumption, ballast adjustments, and loading conditions . Therefore, we investigated how resistance changes under three different loading conditions, namely overload, design-load, and lightship, for small craft, using both model experiments and numerical simulations. Additionally, we examined the sensitivity of weight changes to resistance to enhance the performance of ships, ultimately reducing power requirements in support of the International Maritime Organization's (IMO) goal of reducing CO2 emissions by 50% by 2050. We found that weight changes have a more significant impact at low Froude Numbers. Operating under overload conditions, which correspond to a 5% increase in draft and an 11.1% increase in displacement, can lead to a relatively substantial increase in total resistance, up to 15.97% and 14.31% in towing tests and CFD simulations, respectively.