Minimum constraint removal problem for line segments is NP-hard

In the minimum constraint removal ([Formula: see text]), there is no feasible path to move from a starting point towards the goal, and the minimum constraints should be removed in order to find a collision-free path. It has been proved that [Formula: see text] problem is NP-hard when constraints have arbitrary shapes or even they are in shape of convex polygons. However, it has a simple linear solution when constraints are lines and the problem is open for other cases yet. In this paper, using a reduction from Subset Sum problem, in three steps, we show that the problem is NP-hard for both weighted and unweighted line segments.

Sustainable Production Enhancement of Valuable Products Via Operational Rectification

ADNOC LNG lies in the middle stream of the value chain, receiving and processing LP and HP gases from ADNOC Offshore. Supporting ADNOC Upstream's current oil production and future growth strategy while reducing its associated emissions of the process by delivering the associated gases to ADNOC LNG battery limit ADNOC LNG processes associated and non-associated gases to produce LNG (Liquefied Natural Gas), Propane, Butane, Paraffinic Naphtha (P. Naphtha) and Sulfur. LNG constitutes Methane, Ethane and a little Propane and butane, with minimum constraints on GHV and density. In order to deal with market competitiveness in the context of a potentially prolonged low-price environment, ADNOC LNG has embarked on various initiatives to maximize its production by driving agility and efficiency throughout the value chain process. Delivering upon efficiency improvements, one of the contributing studies included optimizing the propane content i.e. reducing the C3 content, in LNG Propane content in LNG has been varied, within operational limits, to maximize production of propane, which is more valuable/profitable when compared to LNG, whilst maintaining minimum LNG specification. In addition, slighting higher feed gas has been processed, to maintain LNG production rate. This has been achieved without hampering the plant stability. The extensive review and analysis of the rectification units has been conducted as well as optimization in terms of temperature profiles and reflux flow rates was able to generate overall better product purification, thereby increasing production of desired and more valuable products. This study has driven the investigation of additional benefits in production enhancement and quality improvements as the market value of Propane is relatively higher than that of LNG and thus yielding greater benefits. The overall performance trial basis deduced a total added benefit equivalent to 9 MMUSD/year YTD for train 3.

Verification of the Polish Geodetic Reference Frame by Means of a New Solution Based on Permanent GNSS Data from the Years 2011-2014

The new solution for the Polish geodetic primary GNSS network was created to verify the currently used reference frame (PL-ETRF2000). The new solution is based on more GNSS data (more daily observation sessions included, a longer data timespan, GLONASS observations added) which were processed in a newer reference frame (IGb08) according to up-to-date methodology and using the latest version of Bernese GNSS Software. The new long-term solution (spanning 3.7 years) was aligned to the IGb08 reference frame using a minimum constraints approach. We categorized Polish reference stations into two categories according to their data length. We obtained good agreement of the new solution with the PL-ETRF2000: for most stations position differences did not exceed 5 mm in horizontal, and 10 mm in vertical components. However, for 30 stations we observed discontinuities in position time series, mostly due to GNSS equipment changes, which occured after the introduction of PL-ETRF2000. Position changes due to the discontinuities reached 9.1 mm in horizontal components, and 26.9 mm in vertical components. The new solution takes into account position discontinuities, and in addition also includes six new stations which were installed after the introduction of the PL-ETRF2000. Therefore, we propose to update the currently-used reference frame for the Polish geodetic primary network (PL-ETRF2000) with the new solution. The new solution was also accepted by the EUREF Technical Working Group as a class A solution (highest accuracy) according to EUREF standards.

Efficient Mining of Partial Periodic Patterns with Individual Event Support Thresholds Using Minimum Constraints

Partial periodic patterns are commonly seen in real-life applications and provide useful prediction with uncertainty. Most previous approaches have set a single minimum support threshold for all events to assume they have similar frequencies which is not practical for real-world applications. Instead of setting a single minimum support threshold for all events, Chen et al. proposed an FP-tree-like algorithm to allow multiple minimum supports for reflecting the natures of the events. However, such a tree-based algorithm encountered an efficiency problem while period length is long or event sequential orders in period segments are varied. Under the circumstance, many tree branches are created and much execution time is spent to find partial periodic patterns. In this paper, we thus propose a projection-based algorithm which examines only prefix subsequences and projects only corresponding postfix subsequences with multiple minimum supports to quickly find the partial periodic patterns in a recursive process. Experiments on both synthetic and real-life datasets show that the proposed algorithm is more efficient than the previous one.

Extraction of the deterministic ingredient of a dynamic geodetic control network

Extraction of the deterministic ingredient of a dynamic geodetic control networkA minimum constraints solution, which resolves the datum defect of a control network, is an arbitrary solution that may result in a systematic error in the estimation of the deformation parameters. This error is not derived from measurements and is usually inconsistent with the geophysical reality. A free network is affected only by errors of measurement and, therefore, a free network is an accepted way of coping with this problem. Study of deformations, which is based on the use of geodetic measurements, is usually performed today by defining a kinematic model. Such a model, when used to describe a complex geophysical environment, can lead to the partial estimation of the deterministic dynamics, which characterize the entire network. These dynamics are themselves expressed in measurements, as the adjustment systems' residuals. The current paper presents an extension of the definition of the parameters that are revalued. This extension enables the cleaning of measurements by means of the extraction of datum elements that have been defined by geodetic measurement. This cleaning minimizes the effects of these elements on the revaluated deformation. The proposed algorithm may be applied to achieve the simultaneous estimation of the physical parameters that define the geophysical activity in the network.