• Title/Summary/Keyword: analysis and design

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A Study for Optimization of Armed Flight Test Ammunition Requirement for the Development of Attack Helicopter (공격헬기 개발을 위한 무장 비행시험 탄약발수 최적화 연구)

  • Lee, Myeong-Seok;Hur, Jang-Wook
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.21 no.8
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    • pp.147-153
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    • 2020
  • Developments in aircraft require safety verification through flight testing for many hours with prototype design and production. The test evaluation step of performing flight tests was an important process that determines the success in the development of the system. In particular, safety development through flight tests in the armed flight test is important for the development of attack helicopters. In the development of attack helicopters, the evaluation period and cost related to the armed flight test are closely related to the required ammunition requirement. Therefore, this paper presents the amount of ammunition required for the military flight test between attack helicopter developments through an analysis of the AH-1 helicopter in a similar case and ADS-44-HDBK of military specification. The AH-1 can be used to calculate the ammunition demand by considering the exclusion of redundant firing tests and configuration differences. In the case of the machine gun-equipped configuration, approximately 10,500R was required, and approximately 324R was required in the case of a rocket-mounted configuration. In addition, if the armed integrated bench is used properly, it is expected to promote efficiently the flight test in the armed flight by identifying the possible risk factors with armed flight tests and excluding them.

Design of V-Band Waveguide Slot Sub-Array Antenna for Wireless Communication Back-haul (무선통신 백-홀용 V-밴드 도파관 슬롯 서브-배열 안테나의 설계)

  • Noh, Kwang-Hyun;Kang, Young-Jin
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.7
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    • pp.334-341
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    • 2016
  • In this paper, the study of a waveguide aperture-coupled feed-structured antenna has been conducted for the purpose of applying it to a wireless back-haul system sufficient for high-capacity gigabits-per-second data rates. For this study, a $32{\times}32$ waveguide slot sub-array antenna with a corporate-feed structure was designed and produced. Also, this antenna is used at 57 GHz to 66 GHz in the V-band. The construction of the antenna is a laminated form with radiating parts (outer groove and slot, cavity), a coupled aperture, and feeds in each. The antenna was designed with HFSS, which is based on 3D-FEM, produced with aluminum processed by a precision-controlled milling machine, and assembled after a silver-plating process. The measurement result from analysis of the characteristics of the antenna shows that return loss is less than -12 dB, VSWR < 2.0, and a wide bandwidth ranges up to 16%. An overall first side lobe level is less than -12.3 dB, and a 3 dB beam width is narrow at about $1.85^{\circ}$. Also, antenna gain is 38.5 dBi, offering high efficiency exceeding 90%.

Two Class Approximation of TLB (Tomato Late Blight) Activity Data (토마토 역병균 항균 활성 데이터의 이분번 근사모델링)

  • Hahn, Hoh-Gyu;M.D., Ashek Ali;Cho, Seung-Joo
    • The Korean Journal of Pesticide Science
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    • v.9 no.2
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    • pp.140-145
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    • 2005
  • Quantitative Structure Activity Relationship (QSAR) assumes the relatedness between physical property and biological activity. However, activity data measured at single concentration such as percent activity have not been used extensively for modeling purpose. This probably comes from the fact that these values are qualitative instead of quantitative. To utilize percent activity data for molecular modeling, we classified the whole data into two classes. One class represents the active while the other signifies the inactive. The percent activity data of ${\beta}$-Ketoacetoanilides measured for TLB (Tomato Late Blight) were investigated. CoMFA (Comparative Molecular Field Analysis) was used as a discriminant function. Using CoMFA provides 3D (three dimensional) information, which is crucial for chemical insight. It can also serve as a predictive model. The resultant model classified the given data correctly (98%). When LOO (leave-one-out) crossvalidation procedure was applied, the classification accuracy was 69%. Therefore two class approximation of percent activity data with CoMFA can be utilized to understand the relationship between chemical structure and biological activity and design subsequent chemical analogs.

Low-power FFT/IFFT Processor for Wireless LAN Modem (무선 랜 모뎀용 저전력 FFT/IFFT프로세서 설계)

  • Shin Kyung-Wook
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.11A
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    • pp.1263-1270
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    • 2004
  • A low-power 64-point FFT/IFFT processor core is designed, which is an essential block in OFDM-based wireless LAM modems. The radix-2/418 DIF (Decimation-ln-Frequency) FFT algorithm is implemented using R2SDF (Radix-2 Single-path Delay Feedback) structure. Some design techniques for low-power implementation are considered from algorithm level to circuit level. Based on the analysis on infernal data flow, some unnecessary switching activities have been eliminated to minimize power dissipation. In circuit level, constant multipliers and complex-number multiplier in data-path are designed using truncation structure to reduce gate counts and power dissipation. The 64-point FFT/IFFT core designed in Verilog-HDL has about 28,100 gates, and timing simulation results using gate-level netlist with extracted SDF data show that it can safely operate up to 50-MHz@2.5-V, resulting that a 64-point FFT/IFFT can be computed every 1.3-${\mu}\textrm{s}$. The functionality of the core was fully verified by FPGA implementation using various test vectors. The average SQNR of over 50-dB is achieved, and the average power consumption is about 69.3-mW with 50-MHz@2.5-V.

Improvement of Fatigue Model of Concrete Pavement Slabs Using Environmental Loading (환경하중을 이용하는 콘크리트 포장 슬래브 피로모형의 개선)

  • Park, Joo-Young;Lim, Jin-Sun;Kim, Sang-Ho;Jeong, Jin-Hoon
    • International Journal of Highway Engineering
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    • v.13 no.4
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    • pp.103-115
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    • 2011
  • Concrete slab curls and warps due to the uneven distribution of temperature and moisture and as the result, internal stress develops within the slab. Therefore, environmental loads must be considered in addition to the traffic loads to predict the lifespan of the concrete pavement more accurately. The strength of the concrete slab is gradually decreases to a certain level at which fatigue cracking is generated by the repetitive traffic and environmental loadings. In this study, a new fatigue regression model was developed based on the results from previously performed studies. To verify the model, another laboratory flexural fatigue test program which was not used in the model development, was conducted and compared with the predictions of other existing models. Each fatigue model was applied to analysis logic of cumulative fatigue damage of concrete pavement developed in the study. The sensitivity of cumulative fatigue damage calculated by each model was analyzed for the design factors such as slab thickness, joint spacing, complex modulus of subgrade reaction and the load transfer at joints. As the result, the model developed in this study could reflect environmental loading more reasonably by improving other existing models which consider R, minimum/maximum stress ratio.

Analysis of the trends of research education on death (죽음준비교육의 연구동향 분석)

  • Kim, Sin-Hayng;Byun, Soung-Won
    • Journal of Digital Convergence
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    • v.12 no.12
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    • pp.469-475
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    • 2014
  • This study analyzed the studies and their trends, specifically 124 master's and doctoral theses, as well as research papers on the topic of education on death published from 1990 to 2014. The study's findings are as follows. First, in terms of trends by year, there were only 8papers in the 1990s but this figure saw a dramatic jump from 2005 to 2009 to a total of 50papers(40.3%). The majority of them, 59papers in total, were master's theses(47.6%). Second, in terms of the study field, theological studies took the lead and studies on social welfare accounted for 29papers(28.4%) which was the largest share. Third, in terms of study subjects, senior citizens were used in the majority of papers or 35papers(40.7%) in total. Fourth, in terms of methodology, literature studies accounted for 61papers(49.2%) which was the largest share. Fifth, for mediation programs education on death, the preferred method of study was to have a before-after design using a control group and experiment group. The most common number of total sessions was 5-8sessions with one session per week and each session lasting for about 100-120minutes. Sixth, as for the effect variable of mediation programs for education on death, death anxiety was the most frequently studied variable at 23 papers(31.5%).

A Study on Maximum Responses of Rotational Shells Subjected to Uneven Settlements by Stochastic Method (부등침하를 받는 회전 쉘의 최대응답 추정에 관한 연구)

  • 정명채
    • Computational Structural Engineering
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    • v.10 no.3
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    • pp.175-184
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    • 1997
  • The objective of this paper is to study arelationship between maximum response and its standard deviation of rotational shells that are subjected to uneven settlements. For this, the ratio, .eta, of the maximum response to standard deviation and it's approximate, .eta./sub apr/, are investigated by stochastic methods. Also, an equation for .eta./sub apr/, that is a function of predominant harmonic number is suggested. The settlements are represented by the Fourier series. Each term in the series contains two coefficients; the amplitude and the phase angle. It is assumed that phase angles are random variables and amplitudes are deterministic. To investigate the characteristics of .eta. and .eta./sub apr/, 100 phase angles for two types of artificial amplitudes spectra are used in the analysis. .eta. and .eta./sub apr/, are almost constant regardless of amplitude type, position of a shell or type of responses; they fall into from 2.0 to 2.5. .eta./sub apr/ is always close to .eta., but tends to be somewhat greater. It may be concluded that a maximum responses of rotational shells subjected to uneven settlements are .eta./sub apr/ (about 2.5) times of its standard deviation. It is considered that this result is used when we design rotational shell structures subjected to differential settlements.

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A Study of Governing Factors on the Engineering Behaviour of a Single Pile in Consolidating Ground (압밀이 진행중인 지반에 설치된 말뚝의 공학적 거동을 지배하는 주요인자들에 대한 연구)

  • Kim, Sung-Hee;Jeon, Young-Jin;Kim, Jeong-Sub;Lee, Cheol-Ju
    • Journal of the Korean GEO-environmental Society
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    • v.18 no.5
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    • pp.5-16
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    • 2017
  • In the present work, a number of advanced three-dimensional (3D) parametric finite element numerical analyses have been conducted to study the behaviour of a single pile in consolidating ground from coupled consolidation analyses. A single pile with typical minimum and maximum ranges of fill height and clay stiffness has been modelled. The computed results demonstrate that the higher the height of the fill above the clay surface and the smaller the stiffness of the clay, the higher the dragloads and the negative skin friction-induced pile settlements. It has been found that the development of dragloads and pile settlement is more governed by the stiffness of the clay rather than the height of the fill. Positive shaft resistance is mobilised only after the average degree of consolidation is larger than 50%. Although the pile is installed when the degree of consolidation is 50% or more, relatively large negative skin friction can nevertheless develop on the pile. On the other hand, when a load is applied on the pile experiencing an increase in the negative skin friction with time during consolidation, the pile undergoes a large increase in the final settlement of up to 95% compared to that of a pile without axial load on the pile head. The allowable pile capacity when there is negative skin friction on the pile is reduced by about 4-11% compared to a pile without negative skin friction.

A Study on Limesurvey in the Form of Open Source Online Survey System for Curriculum Organizing (학교 교육과정 편성을 위한 오픈 소스 온라인 설문조사 시스템 Limesurvey 활용 방안)

  • Han, Ki-Sun;Chun, Seok-Ju
    • 한국정보교육학회:학술대회논문집
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    • 2011.01a
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    • pp.91-101
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    • 2011
  • The purpose of this paper is to quickly identify school parents, teachers, students, community needs and opinions for curriculum organizing and the implementation of an online survey system for operating educational activities. Online survey system should be implemented based on Limesurvey to reduce costs and administrative costs. Limesurvery is available without the development of the separate program and offers the form of web-based template system, complete design, layout. Also, Limesurvey offers basic statistical analysis of survey data. Limesurvey can be executed by installing the program on a web hosting, typing database information. Limesurvey can be made a graph of the statistical results. Besides, Limesurvery can be stored in the form of HTML, Word, Excel, CSV Files and can be stured as basic datas for SPSS or PASW, R data, other statistical processing programs. If we could be operate Limesurvey in the form of open source-based survey program in elementary school, we could be reduced teacher's unnecessary work for statistics and overcame the problem of offline survey system.

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A Study on the Next VWorld System Architecture: New Technology Analysis for the Optimal Architecture Design (차세대 브이월드 시스템 아키텍처 구성에 관한 연구: 최적의 아키텍처 설계를 위한 신기술 분석)

  • Go, Jun Hee;Lim, Yong Hwa;Kim, Min Soo;Jang, In Sung
    • Spatial Information Research
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    • v.23 no.4
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    • pp.13-22
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    • 2015
  • There has been much interest in the VWorld open platform with the addition of a variety of contents or services such as 2D map, 3D terrain, 3D buildings, and thematic map since 2012. However, the VWorld system architecture was not stable for the system overload. For example, the system was stopped due to the rapidly increasing user accesses when the 3D terrain service of the North Korea and the Baekdu mountain was launched at September 2012 and September 2013, respectively. It was because the system architect has just extended the server system and the network bandwidth whenever the rapid increase of user accesses occurs or new service starts. Therefore, this study proposes a new VWorld system architecture that can reliably serve the huge volume of National Spatial Data by applying the new technologies such as CDN, visualization and clustering. Finally, it is expected that the results of this study can be used as a basis for the next VWorld system architecture being capable of a huge volume of spatial data and users.