• Title/Summary/Keyword: Back-testing

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Will CFD ever Replace Wind Tunnels for Building Wind Simulations?

  • Phillips, Duncan A.;Soligo, Michael J.
    • International Journal of High-Rise Buildings
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    • v.8 no.2
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    • pp.107-116
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    • 2019
  • The use of computational fluid dynamics (CFD) is becoming an increasingly popular means to model wind flows in and around buildings. The first published application of CFD to both indoor and outdoor building airflows was in the 1970's. Since then, CFD usage has expanded to include different aspects of building design. Wind tunnel testing (WTT) on buildings for wind loads goes back as far as 1908. Gustave Eiffel built a pair of wind tunnels in 1908 and 1912. Using these he published wind loads on an aircraft hangar in 1919 as cited in Hoerner (1965 - page 74). The second of these wind tunnels is still in use today for tests including building design ($Damljanovi{\acute{c}}$, 2012). The Empire State Building was tested in 1933 in smooth flow - see Baskaran (1993). The World Trade Center Twin Towers in New York City were wind tunnel tested in the mid-sixties for both wind loads, at Colorado State University (CSU) and the [US] National Physical Laboratory (NPL), as well as pedestrian level winds (PLW) at the University of Western Ontario (UWO) - Baskaran (1993). Since then, the understanding of the planetary boundary layer, recognition of the structures of turbulent wakes, instrumentation, methodologies and analysis have been continuously refined. There is a drive to replace WTT with computational methods, with the rationale that CFD is quicker, less expensive and gives more information and control to the architects. However, there is little information available to building owners and architects on the limitations of CFD for flows around buildings and communities. Hence building owners, developers, engineers and architects are not aware of the risks they incur by using CFD for different studies, traditionally conducted using wind tunnels. This paper will explain what needs to happen for CFD to replace wind tunnels. Ultimately, we anticipate the reader will come to the same conclusion that we have drawn: both WTT and CFD will continue to play important roles in building and infrastructure design. The most pressing challenge for the design and engineering community is to understand the strengths and limitations of each tool so that they can leverage and exploit the benefits that each offers while adhering to our moral and professional obligation to hold paramount the safety, health, and welfare of the public.

Testing case analysis of Database Software (데이터베이스 소프트웨어의 시험 사례 분석)

  • Yang, Hae-Sool;Kang, Bae-Keun;Lee, Ha-Yong
    • Journal of the Korea Society of Computer and Information
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    • v.14 no.5
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    • pp.167-174
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    • 2009
  • The meaning of Database in order to manage the data which is huge in the meeting of the record which logically had become the fire tube or file 'efficiently' is widely used from the place which controls a many double meaning data. Like this data base it creates, it manages, the programs which send an answer back according to demand of the user as DBMS it calls. Like this it will be able to grasp the quality level of the data base software product which is important index from the research which index it buys it defined. Also, in order to produce the result of index it selects the collection item which is necessary and collection and analysis it leads and what kind of defect types occur substantially mainly, and it confirmed and the test and evaluation model in about data base software and a tentative instance it developed it analyzed.

A Study on the Usefulness of Backend Development Tools for Web-based ERP Customization (Web기반 ERP 커스터마이징을 위한 백엔드 개발도구의 유용성 연구)

  • Jung, Hoon;Lee, KangSu
    • Journal of the Korea Convergence Society
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    • v.10 no.12
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    • pp.53-61
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    • 2019
  • The risk of project failure has increased recently as ERP systems have been transformed into Web environments and task complexity has increased. Although low-code platform development tools are being used as a way to solve this problem, limitations exist as they are centered on UI. To overcome this, back-end development tools are required that can be developed quickly and easily, not only from the front development but also from a variety of development sources produced from the ERP development process, including back-end business services. In addition, the development tools included within existing ERP products require a lot of learning time from the perspective of beginner and intermediate developers due to high entry barriers. To address these shortcomings, this paper seeks to study ways to overcome the limitations of existing development tools within the ERP by providing customized development tool functions by enhancing the usability of ERP development tools suitable for each developer's skills and roles based on the requirements required by ERP development tools, such as reducing the time required for querying, automatic binding of data for testing for service-based units, and checking of source code quality.

The study of difference between HIVD group and simple low back pain group by Current Perception Threshold test (요추추간판탈출증군과 단순요통군간의 Current Perception Threshold상의 차이에 관한 연구)

  • Kim Cheol-Hong;Lee Byung-Hoon;Kwon Hye-Yeon;Lim Chun-Woo;Seo Jung-Chul;Youn Hyoun-Min;Song Choon-Ho;Jang Kyung-Jeon;Ahn Chang-Beohm
    • Journal of Acupuncture Research
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    • v.18 no.6
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    • pp.59-69
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    • 2001
  • Objective : The aim of this study is to assess the ability of the CPT test to dignosis radiculopathy in Korean with NeuvalTM CPT database. Method : Electrical stimulation(at 2000, 250, and 5Hz) using Neurometer was applied to the 19 patients who felt back and sciatic pain with herniated intervertevral disc(HIVD) of L-spine, dignosisd by lumbar CT or MRI, and the 33 patients who felt only back or hip or leg pain without HIVD, stenosis, spondylolisthesis which causing radiculopathy. The test sites were toe1, toe3 and toe5 related to L4, L5 and S1 nerve roots. Results : The mean values of the CPT of HIVD group was stiatically lower than LBP group at toe1-250Hz, toe3-2000Hz, 250Hz and toe5-250Hz, 5Hz. The grading CPT score of HIVD group was stastically higher than LBP group at the toe3(L5). The VAS of HIVD group was stastically higher than LBP group. Conclusion : These results suggest that the CPT test can be a valuable testing for diagnosing radiculopathy in Korean. In using CPT test further study is needed for the diagnosis and evaluation of sensory nerve dysfunction in the musculoskeletal disease.

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Adjustment of 1st order Level Network of Korea in 2006 (2006년 우리나라 1등 수준망 조정)

  • Lee, Chang-Kyung;Suh, Young-Cheol;Jeon, Bu-Nam;Song, Chang-Hyun
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.26 no.1
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    • pp.17-26
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    • 2008
  • The 1st order level network of Korea was adjusted simultaneously in 1987. After that, the 1 st order level network of Korea was adjusted simultaneously by National Geographic Information Institute in 2006. The levelling data were acquired by digital level with invar staff from 2001 through 2006. The 1st order level network consists of 36 level lines. Among them, 34 level lines comprise 11 level loops. Among 36 level lines, 4 level lines have fore & back error larger than the regulations for the 1st order levelling of NGII, Korea. Also, the closing error of 3 loops of level network exceed the regulation for the 1st order levelling of NGII. The standard error of fore and back leveling between bench marks(${\eta}_1$) are distributed between 0.2 $mm/{\surd}km$ and 1.7 $mm/{\surd}km$. The standard error of loop closing(${\eta}_2$) is 2.0 $mm/{\surd}km$. This result means that the 1st order level network of Korea qualifies for the high precision leveling defined by International Geodetic Association in 1948. As the result of the 1st order level network adjustment, the reference standard error($\hat{{\sigma}_0}$) of the level network was 1.8 $mm/{\surd}km$, which is twice as good as that of the 1st adjustment of level networks in 1987.

Fingerprint Verification Based on Invariant Moment Features and Nonlinear BPNN

  • Yang, Ju-Cheng;Park, Dong-Sun
    • International Journal of Control, Automation, and Systems
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    • v.6 no.6
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    • pp.800-808
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    • 2008
  • A fingerprint verification system based on a set of invariant moment features and a nonlinear Back Propagation Neural Network(BPNN) verifier is proposed. An image-based method with invariant moment features for fingerprint verification is used to overcome the demerits of traditional minutiae-based methods and other image-based methods. The proposed system contains two stages: an off-line stage for template processing and an on-line stage for testing with input fingerprints. The system preprocesses fingerprints and reliably detects a unique reference point to determine a Region-of-Interest(ROI). A total of four sets of seven invariant moment features are extracted from four partitioned sub-images of an ROI. Matching between the feature vectors of a test fingerprint and those of a template fingerprint in the database is evaluated by a nonlinear BPNN and its performance is compared with other methods in terms of absolute distance as a similarity measure. The experimental results show that the proposed method with BPNN matching has a higher matching accuracy, while the method with absolute distance has a faster matching speed. Comparison results with other famous methods also show that the proposed method outperforms them in verification accuracy.

A Study on Numerical Modeling of Dynamic CPT using Particle Flow Code (입자결합모델을 이용한 동적콘관입시험(DCPT)의 수치해석 모델링에 관한 연구)

  • You, Kwang Ho;Lee, Chang Su;Choi, Jun Seong
    • International Journal of Highway Engineering
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    • v.16 no.2
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    • pp.43-52
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    • 2014
  • PURPOSES : To solve problems in current compaction control DCPT(Dynamic Cone Penetrometer Test), highly correlated with various testing methods, simple, and economic is being applied. However, it、s hard to utilize DCPT results due to the few numerical analyses for DCPT have been performed and the lack of data accumulation. Therefore, this study tried to verify the validation of numerical modeling for DCPT by comparing and analyzing the results of numerical analyses with field tests. METHODS: The ground elastic modulus and PR(Penetration Rate) value were estimated by using PFC(Particle Flow Code) 3D program based on the discrete element method. Those values were compared and analyzed with the result of field tests. Also, back analysis was conducted to describe ground elastic modulus of field tests. RESULTS : Relative errors of PR value between the numerical analyses and field tests were calculated to be comparatively low. Also, the relationship between elastic modulus and PR value turned out to be similar. CONCLUSIONS : Numerical modeling of DCPT is considered to be suitable for describing field tests by carrying out numerical analysis using PFC 3D program.

Application of hydraulic cylinder testing to determine the geotechnical properties of earth-filled dams

  • Rodriguez, Roman F.;Nicieza, Celestino G.;Gayarre, Fernando L.;Lopez, Francisco L. Ramos
    • Geomechanics and Engineering
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    • v.9 no.4
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    • pp.483-498
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    • 2015
  • This article describes a new in-situ load test called the Hydraulic Cylinder Test (HCT) and its application to determine the geotechnical properties of soil-rock mixtures. The main advantages of the test are its easy implementation, speed of execution and low-cost. This article provides a detailed description of the equipment and the test procedure, and examines a case study of its application to determine the geotechnical properties of an earth-filled dam for a tailings pond. The containment dams of the ponds are made from blocks of gypsum and marl, obtained from the excavation of the ponds, mixed in a matrix of sands and clays. The size of the rocks varies between 1 and 30 cm. The HCT is particularly useful for determining the geotechnical properties of this type of soil-rock mixture. Nine HCTs were carried out to determine its strength (c, ${\phi}$) and deformation (B, G) properties. The results obtained were validated using the Bim strength criterion, recently proposed, and some pressure meter tests carried out beforehand. The properties obtained are used to analyze the stability of the dam using computer simulations and a modification to its design is proposed.

The Nail Jointing Properties and Checking Mechanism of Thinned Japanese Cedar (Cryptomeria japonica D. Don.) Boards Grown in Southern District (남부지역 삼나무 간벌목재의 못접합특성과 할렬발생)

  • So, Won-Tek
    • Journal of the Korea Furniture Society
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    • v.22 no.1
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    • pp.18-25
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    • 2011
  • This experiment was carried out to investigate the effects of nail diameter, driving distance from end on the nail check length, and the effects of nail diameter, prehole for nail driving, and nail driving slope on the nail withdrawal resistance, by the static test of universal testing machine. The test specimen were Japanese cedar (Cryptomeria japonica D. Don.) boards grown in southern district of Korea, and the nails for test were 2.02~4.82 mm in diameter. After nail driving, the back face checks of test boards were longer than the surface checks. The optimum nail diameter without checks or loss of nail withdrawal resistance were below 10% of board width and the optimum driving distance from end of boards were ten multiple of nail diameter. The relation between nail diameter (x) and withdrawal resistance (y) was linear and the regression formulae for Japanese cedar board was y = 8.66x + 7.6 ($R^2=0.978$). As both of the prehole diameter and driving slope were increased, the withdrawal resistances were significantly decreased.

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The Development of Pants Pattern for the Improvement of Obese Women's Fit (피트성 향상을 위한 비만여성의 바지패턴 개발)

  • Lee, Jin-Suk;Lee, Jeong-Ran
    • Fashion & Textile Research Journal
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    • v.13 no.2
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    • pp.253-262
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    • 2011
  • The purpose of this study was improvement of the pants fit for obese women. The results were as follows; 5 obese women in their 20s and 30s were selected for the testing 3D body. They showed no significant differences in all items, comparing with the data of 5th Size Korea body dimensions. The average waist circumstance of the subjects' 3D body dimensions was 87.0 cm and hip circumstance was 102.4 cm, and their obese body types had similar mean values. Based on the survey results and the 3D body dimensions of 5th Size Korea body dimensions, a pants pattern to supplement their body type and improve a fit was designed with waist circumference(88 cm), hip circumference(103 cm), crotch length(27.1 cm), thigh circumference(62 cm), pants length(97 cm), pants hem line circumference(44 cm). Based on the detailed design of ready made pants and the study results of young obese women's preference for pants design, pants of straight silhouette and semi-tight fit which have waist line lowered by 3.5 cm from the waist circumference line, 3.5 cm belt width, no front dart and one back dart, were manufactured with 100% black cotton and cotton spandex mixed fabrics.