• 제목/요약/키워드: Multi-step

검색결과 1,474건 처리시간 0.029초

A Multi-step Time Series Forecasting Model for Mid-to-Long Term Agricultural Price Prediction

  • Jonghyun, Park;Yeong-Woo, Lim;Do Hyun, Lim;Yunsung, Choi;Hyunchul, Ahn
    • 한국컴퓨터정보학회논문지
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    • 제28권2호
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    • pp.201-207
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    • 2023
  • 본 논문에서는 Multi-Step Time Series의 세 가지 전략을 비교 분석하기 위해 LGBM, MLP, LSTM, GRU를 사용하여 농산물 중장기 가격 예측에 대한 최적의 모형을 제안한다. 제안 모형은 다각도로 전략을 선택하여 모델과 전략간 최적의 조합을 찾도록 설계되었다. 기존 농산물 가격 예측 연구에서는 전통 계량경제 모델인 ARIMA를 비롯하여 LSTM 계열 모델이 주로 사용된 반면 Multi-Step Time Series 관련 농산물 가격 예측 연구는 매우 제한적이다. 본 연구에서는 농산물 가격의 변동성 정도에 따라 두 개의 기간으로 나누어 실험을 진행하였으며, Direct, Hybrid, Multiple Outputs 등 세 전략의 중장기 가격 예측 결과 Hybrid 접근법이 상대적으로 우수한 성능을 보였다.본 연구 결과는 중장기 일별 가격 예측을 고도화할 수 있는 효과적인 대안을 제시한다는 측면에서 학술적, 실무적 의의를 갖는다.

SVC를 위한 새로운 이중접속방식의 멀티스텝 인버터 (New Double-Connected Multi-Step Inverter for SVC)

  • 최세완;양승욱;김기용
    • 전력전자학회:학술대회논문집
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    • 전력전자학회 1999년도 전력전자학술대회 논문집
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    • pp.460-463
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    • 1999
  • A new multi-step voltage source inverter is proposed in this paper. The proposed scheme is composed of the double-connected 12-step inverter with an auxiliary circuit. The auxiliary circuit includes two voltage dividing capacitors, two switching devices and a low KVA autotransformer. The resultant system is shown to be a 24-step inverter suitable for large scale SVC applications in which the PWM method can not be employed. The design parameters are derived from the analysis of voltages and currents by means of switching functions. The simulation results verify the proposed concept.

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Development of higher performance algorithm for dynamic PIV

  • NISHIO Shigeru
    • 한국가시화정보학회:학술대회논문집
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    • 한국가시화정보학회 2004년도 Proceedings of 2004 Korea-Japan Joint Seminar on Particle Image Velocimetry
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    • pp.25-32
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    • 2004
  • The new algorithm for higher performance of dynamic PIV has been proposed. Present study considered mathematical basis of PIV analysis for multiple-time-step images and it enables us to analyze the high time-resolution PIV, which is obtained by dynamic PIV system. Conventional single pair image PIV analysis gives us the velocity field data in each time step but it sometimes contains unnecessary information of target flow. Present technique utilize multi-time step correlation information, and it is analyzed.

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3D 시뮬레이션과 측정값을 이용한 Q-band 정밀 초소형 동축 어댑터의 설계 (Design Approach of Q-band Precision Subminiature Coaxial Adaptor Using 3D Simulator and Its Experimental Results)

  • 왕종;전정;조원용;김남영
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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    • pp.387-388
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    • 2008
  • This paper presents the design approach and test results of the Q-band precision subminiature coaxial adaptor based on transmission line theory using multi-step impedance and air-holes to increase its cutoff frequency. In order to increase the frequency performance, the adaptor is designed with hooked structure, fixing step, multi-air-holes, and outer conductor. The return loss increments due to the hooked structure and multi air-holes are minimized to 2 dB and 1.5 dB, respectively. A VSWR(Voltage Standing Wave Ratio) of <1.2 is obtained from DC to 40 GHz, while guaranteeing the durability of the adaptor from room-temperature$(25^{\circ}C)$ to $120^{\circ}C$.

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On the natural frequencies and mode shapes of a multi-span and multi-step beam carrying a number of concentrated elements

  • Lin, Hsien-Yuan
    • Structural Engineering and Mechanics
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    • 제29권5호
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    • pp.531-550
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    • 2008
  • This paper adopts the numerical assembly method (NAM) to determine the exact solutions of natural frequencies and mode shapes of a multi-span and multi-step beam carrying a number of various concentrated elements including point masses, rotary inertias, linear springs, rotational springs and springmass systems. First, the coefficient matrix for an intermediate station with various concentrated elements, cross-section change and/or pinned support and the ones for the left-end and right-end supports of a beam are derived. Next, the overall coefficient matrix for the entire beam is obtained using the numerical assembly technique of the conventional finite element method (FEM). Finally, the exact solutions for the natural frequencies of the vibrating system are determined by equating the determinant of the last overall coefficient matrix to zero and the associated mode shapes are obtained by substituting the corresponding values of integration constants into the associated eigenfunctions.

Designing a nanocrystal-based temperature and strain multi-sensor with one-step inkjet printing

  • Bang, Junsung;Ahn, Junhyuk;Oh, Soong Ju
    • 센서학회지
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    • 제30권4호
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    • pp.218-222
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    • 2021
  • Wearable multi-sensors based on nanocrystals have attracted significant attention, and studies on patterning technology to implement such multi-sensors are underway. Conventional patterning processes may affect material properties based on high temperatures and harsh chemical conditions. In this study, we developed an inkjet printing technique that can overcome these drawbacks through the application of patterning processes at room temperature and atmospheric pressure. Nanocrystal-based ink is used to adjust properties efficiently. Additionally, the viscosity and surface tension of the solvents are investigated and optimized to increase patterning performance. In the patterning process, the electrical, electrothermal, and electromechanical properties of the nanocrystal pattern are controlled by the ligand exchange process. Experimental results demonstrate that a multi-sensor with a temperature coefficient of resistance of 3.82 × 10-3 K-1 and gauge factor of 30.6 can be successfully fabricated using one-step inkjet printing.

경방향 진동모드를 이용한 적층형 압전변압기의 강압특성 (Step-Down Characteristics of Multi-layed Piezo Transformer for Transverse Vibration Mode)

  • 정현호;박태곤;김명호
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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    • pp.340-343
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    • 2003
  • This paper presents characteristics of piezo transformer for AC-DC converter. This transformer uses transverse vibration mode and the origin of the structure was the ring dot type transformer. Because, the ring dot type transformers produce only step-up phenomenon, we made a multi-layered ring dot structure for a step-down output. The characteristics of the transformer were simulated by using the ANSYS. And frequency and voltage were measured by changing the load resistance and current. Frequencies that have the maximum output voltage and current were gradually increased, when the resistance were increased. Output voltage and current show a stable linearity according to the input voltage. The maximum output power was expected greater than 20 [W]. So, we expect that this type of multi-layered step-down ring dot transformer can be adopted for a small AC adapters.

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다단계최적화방법에 의한 선박구조물의 동특성의 최적변경법에 관한연구 (Study on Optimum Modification Method of Dynamic Charcteristics of Ship Structures by Multi-level Optimization)

  • 박석주
    • Journal of Advanced Marine Engineering and Technology
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    • 제23권4호
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    • pp.574-582
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    • 1999
  • This paper discusses the multi-level optimization method in dynamic optimization problems through stiffened plate of ship structures. In structural optimization the computational cost increases rapidly as the number of design variables increases. And we need a great amount of cal-culation and time on problems of modified dynamic characteristics of large and complicated struc-tures. In this paper the multi-level optimization is proposed which decreases computational time and cost. the dynamic optimum designs of stiffened plate that control the natural frequency and minimize weight subjected to constraints condition are derived. The way to apply the multi-level optimization methods in this study follow: In the first step the dynamic characteristics is controlled for the two-dimensional model of stiffened plate by sensitivity analysis and quasi-least squares methods. In the second step the cross-section of the stiffener is decided so that the weight is minimized under needed constraints by the steepest descent or ascent method. In the third the three-dimensional model is made based on the results of the first step and the second step confirmation and finer tuning of the objective function are carried out. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate.

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그래핀 원스텝 전사(Graphene One-Step Transfer) 공정 기반 다층 그래핀 잔여분말 제거 기술 연구 (A Study on Residual Powder Removing Technique of Multi-Layered Graphene Based on Graphene One-Step Transfer Process)

  • 우채영;조영수;홍순규;이형우
    • 한국분말재료학회지
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    • 제26권1호
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    • pp.11-15
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    • 2019
  • In this study, a method to remove residual powder on a multi-layered graphene and a new approach to transfer multi-layered graphene at once are studied. A graphene one-step transfer (GOST) method is conducted to minimize the residual powder comparison with a layer-by-layer transfer. Furthermore, a residual powder removing process is investigated to remove residual powder at the top of a multi-layered graphene. After residual powder is removed, the sheet resistance of graphene is decreased from 393 to 340 Ohm/sq in a four-layered graphene. In addition, transmittance slightly increases after residual powder is removed from the top of the multi-layered graphene. Optical and atomic-force microscopy images are used to analyze the graphene surface, and the Ra value is reduced from 5.2 to 3.7 nm following residual powder removal. Therefore, GOST and residual powder removal resolve the limited application of graphene electrodes due to residual powder.

상용압연 형강과 콘크리트 합성거더의 다단계 긴장력 최적설계 (Optimal Tension Forces of Multi-step Prestressed Composite Girders Using Commercial Rolled Beams)

  • 정홍시;김영우;박재만;신영석
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 2004년도 봄 학술발표회 논문집
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    • pp.95-102
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    • 2004
  • The 1st and 2nd tension forces of the PSSC(Prestressed Steel and Concrete) girder constructed with commercial rolling beams and concrete are optimally designed. The design variables are the 1st and 2nd tension forces due to multi-step prestressing and live load. The objective function is set to the maximum live load. Design conditions are allowable stress at the top and bottom of slab, beam and infilled concrete due to a construction step. An Optimization of Matlab based program Is developed. The results show that the tendon position and concrete compression strength etc are important.

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