Simulation modelling of mechanical systems for intra-row weeding in a precision farming approach

Aim of study: To test new approaches to perform mechanical weeding inside the row in horticulture and tree fruit fields. The idea is to weed the row by skipping the crop by means of a rotating system instead of a traditional crosswise one. Area of study: North of Italy. Material and methods: Numerical models have been developed to simulate mechanical weeding over time by generating numerical maps to quantify the different kind of worked areas. Main results: Considering the efficiency of weed control on the row, the rotating plant-skipping system with vertical axis (RPSS-VA model) with two working tools gives the best performance index (1.1.RWA% = 95.9%). A similar performance can be obtained by the crosswise displacement plant-skipping system (CDSS model, 1.1.RWA% = 95.9 %), but with very high crosswise translation velocity (with va/vr ratio = 1/5, 1.1.RWA% = 94.5%). With regard to the outwards worked area the RPSS-VA models give the best performances (2.2.%OWAR index from 127.2% up to 282.3%). To reduce the worked area outside the row, the FBTS models give lower index (2.1.OWAR%), while the RPSS-HA works only on the row, but with the lower 1.1.RWA% index among all tested models (55.8%). Research highlights: Rotating systems resulted more efficient than traditional ones, and provide considerations on the use of electric drive power instead of hydraulic one. This study highlights also the need of new approaches in designing lighter working tools. Lastly, the proposed classification of the worked areas could be used as reference standard.

Determining the Number of Topics to Retain using Tools from Factor Analysis

Determining the optimal number of topics to retain in the conduct of topic modeling (TM) has received much attention over the last decade. Despite this work, issues remain regarding the best methods to use for making such determinations. Approaches involving the use of relatively simple statistics, most notably perplexity, have proven to be somewhat inconsistent. Recently, researchers have suggested the use of change in perplexity scores as a useful heuristic for determining the optimal number of topics to retain. The current study builds on this earlier work by assessing the utility of several methods borrowed from factor analysis and applied to statistics commonly used in topic modeling, including perplexity and Alpha. These new approaches are applied to several textual datasets and compared with more traditional methods for determining the number of topics to retain. Results of these analyses demonstrate that application of these methods borrowed from factor analysis does appear to be effective for identifying the number of topics to retain.

The Main Threats and Challenges for Russia in the First Half of the XXI Century and Possible Areas of Work to Mitigate their Consequences

This article analyzes threats and challenges for the Russian Federation in the first half of the XXI century and identifies possible directions for improving security in emergency situations based on the use of new approaches in organizational, legal, scientific and technical support of measures, management bodies and civil defense forces and the unified state system of emergency prevention and response (RSChS).