1,721,098 research outputs found
A Metastore-based Data Warehouse Development Methodology
No full textData warehouse (DW) is important for analytical processing. Metadata is a key to its architecture. This paper proposes an architecture that consists of seven components. To illustrate data warehouse environment(DWE), this paper proposes taxonomies having four flows. On the basis of the taxonomies and metadata, this paper proposes a methodology for building the data warehouse and metadata simultaneously. This integrated development methodology (IDM) consists of seven phases: (ⅰ) preparatory phase, (ⅱ) requirement analysis phase, (ⅲ) data warehouse development phase, (ⅳ) operational data store development phase, (ⅴ) data mart development phase, (ⅵ) metastore development phase, and (ⅶ) maintenance phase. A metastore system is proposed to help develop metadata interactively. An illustrative example is investigated to demonstrate the usefulness of IDM
Missile autopilot design for agile turn using time delay control with nonlinear observer
No full textThis paper deals with missile autopilot design for agile turn phase in air-to-air engagement scenarios. To attain a fast response, angle-of-attack (AOA) is adopted for an autopilot command structure. Since a high operational AOA is generally required during the agile turn phase, dealing with the aerodynamic uncertainties can be a challenge for autopilot design. As a remedy, a new controller design method based on robust nonlinear control methodology such as time delay control is proposed in this paper. Nonlinear observer is also proposed to estimate the AOA in the presence of the model uncertainties. The performance of the proposed controller with variation of the aerodynamic coefficients is investigated through numerical simulations. © The Korean Society for Aeronautical & Space Sciences.
From whales to minnows: The impact of crypto-reward fairness on user engagement in social media
No full textIn an era where user-generated content drives social media growth, effectively incentivizing contributions remains a challenge. This study explores the empirical impact of a crypto-integrated platform, Steemit, focusing on a system transition designed to enhance fairness in reward distribution. We assess how this shift affects user engagement, specifically through the volume of posts. Our findings indicate that a fairer crypto-reward distribution boosts user-generated posts, though the increase is less pronounced for users with higher capital or reputation. Further analysis reveals the complex dynamics of cryptocurrency rewards and their role in fostering individual contributions and platform growth, while offering financial incentives. The effects of fair distribution are consistent across diverse user groups, highlighting novel incentivization strategies in social media and the transformative potential of integrating cryptocurrencies into reward systems.
Three-dimensional biased proportional navigation guidance based on spatial rotation of predicted final velocity
Full text linkThis study presents the design of three-dimensional biased proportional navigation guidance laws for arrival at a stationary target along a desired direction based on spatial rotation of predicted final velocity vector. The focus is on full constructive derivation using vector-form expressions without introducing local representation of rotation such as Euler angles or quaternions. The proposed approach synthesises the bias command in the form of an angular velocity vector through realisation of the predictive control design philosophy, the direction which has been unexplored in a three-dimensional setting. The proposed approach avoids heuristic choices and approximations in the design process and hence overcomes the limitation of earlier studies. The vector-form design approach provides theoretical and practical advantages including rigour in derivation, clear geometric understandings about the problem provided by identification of the most effective direction for rotation of final velocity, independence from selection of a fixed coordinate system, avoidance of singularities in local representations, more direct trajectory shaping, and simple implementation
Entry Vehicle Trajectory Optimization using Convex Programming and Post-correction Technique
No full textThis paper considers the trajectory optimization of entry vehicles using convex programming. Optimal entry trajectory satisfying path constraints on heating rate, dynamic pressure, and load factor is btained with sequential second-order cone programming (SOCP). The nonlinear dynamics and path constraints are simplified by changing the independent variable into energy. To mitigate infeasibility and solution divergence problems, the post-correction technique is utilized as well as slack variables and trust-region. The step length of obtained solution at each iteration is modified based on the amount of linearization error. The robustness and effectiveness of the proposed method is demonstrated through numerical simulation
Biased PNG With Terminal-Angle Constraint for Intercepting Nonmaneuvering Targets Under Physical Constraints
No full textA biased proportional navigation guidance law, considering the seeker's look angle and acceleration capability limits, for impact-angle-control against nonmaneuvering targets is proposed. The proposed law consists of two time-varying biases: One is to achieve the desired impact angle within the command limit; the other is to keep the look angle constant for not exceeding the boundary value. Under physical constraints, the maximum achievable impact angle is obtained for practical implementation. The performance of the proposed law is demonstrated through nonlinear simulations.
Enhanced Longitudinal Controller of Hypersonic Vehicle based on Nonlinear Dynamic Inversion with Nonlinear Disturbance Observer
No full textCirculating tumor cells are associated with poor outcomes in early-stage hepatocellular carcinoma: a prospective study
No full textBackgroundPrevious studies evaluating association between circulating tumor cells (CTCs) and clinical outcomes in hepatocellular carcinoma (HCC) have shown inconsistent results due to suboptimal detection methods and patient heterogeneity.MethodsPatients undergoing surgery for early-stage HCC were prospectively enrolled. The CTC numbers were determined using a tapered slit platform, which detects CTCs based on the cell size and morphology. Survival and recurrence were evaluated, and Cox proportional hazards models were used to demonstrate the prognostic significance of CTC.ResultsOf 105 patients, 25 had increased CTC numbers after surgery (Delta CTC>0, defined as positive) and a significantly higher level of recurrence (p=0.042). A positive Delta CTC was seen to be an independent predictor of recurrence (hazard ratio 2.28), along with hepatitis B virus infection, alanine aminotransferase level, and the presence of satellite nodules (all p<0.05). Subgroup analyses showed that a positive Delta CTC was associated with lower survival and higher recurrence among patients with low alpha-fetoprotein levels and cirrhosis (all p<0.05).ConclusionCalculation of Delta CTC based on the physical properties of the cells is predictive of recurrence in patients with early HCC undergoing surgery.
Prediction of Instantaneous Impact Point of Launch Vehicle, Including Drag Effect
No full textThis study proposes an application algorithm for two existing methods to predict the instantaneous impact point of a rocket. The effect of atmospheric drag was modeled to improve the accuracy of the prediction. The Keplerian method assumes that a launch vehicle is in ballistic motion in a global coordinate system. The other method predicts the instantaneous impact point of long-range artillery, which includes modeling the drag effect during free-fall in the local coordinate system. Combining the two methods based on critical altitude improved the prediction accuracy while maintaining real-time performance. The proposed method allows users to select the parameters for the method, which can regulate the prediction accuracy and real-time performance. The performance of the proposed method was verified by comparing it with the performance of the Keplerian method, which is conventionally used for the instantaneous impact point prediction of launch vehicles.
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