Estimation of Turbulent Triplet Covariances for Bora Flows

Bora is a strong or severe, relatively cold, gusty wind that usually blows from the northastern quadrant at the east coast of the Adriatic Sea. In this study bora’s turbulence triplet covariances were analysed, for the first time, for bora flows. The measurements used were obtained from the measuring tower on Pometeno brdo (“Swept-Away Hill”), in the hinterland of the city of Split, Croatia. From April 2010 until June 2011 three components of wind speed and sonic temperature were measured. The measurements were performed on three heights, 10, 22 and 40 m above the ground with the sampling frequency of 5 Hz. During the observed period, total of 60 bora episodes were isolated. We analyse the terms in prognostic equations for turbulence variances. In that respect, the viscous dissipation term was calculated using two approaches: (i) inertial dissipation method (εIDM) and (ii) direct approach from the prognostic equations for variances of turbulence (εEQ). We determine that the direct approach can successfully reproduce the shape of the curve, but the values are for several orders of magnitudes smaller compared to the real data. Further, linear relationship between εIDM and εEQ was obtained. Using the results for εEQ, viscous dissipation rate in longitudinal, transversal and vertical direction was determined. It is shown that viscous dissipation has the greatest impact on bora’s longitudinal direction. The focus is on the turbulence transport term, i.e., the triplet covariance term. For the first time, it is found that turbulence transport is very significant for the intensity of near−surface bora flows. Furthermore, turbulence transport can be both positive and negative, yet intensive. It is mostly negative at the upper levels and positive at the lower levels. Therefore, turbulence transport, in most cases, takes away turbulence variance from the upper levels and brings it down to the lower ones. This is one of the main findings of this study; it adds to the understanding of peculiarities of bora wind, and perhaps some other severe winds.

Adjustment of drilling slurry density during transportation by Platform Supply Vessels

Annotation – The issues of maintaining the drilling fluid density during its transportation from shore to the oil drilling platform by the Platform Supply Vessels were considered. The research was carried out on the vessel of 5650 deadweight tons, which made 2 ... 2.5 day voyages from port to drilling platform with possible waiting for direct approach to the platform for 1 ... 1.5 days. The drilling fluid was transported in four tanks of equal-size, arranged in pairs on each side of the vessel. It was found that during this period of time there is a latent stratification of drilling fluid along the depth of cargo tank, causing stratification of its density. The density of the drilling fluid was measured at depths corresponding to 10, 50 and 90 % of the total tank depth. The drilling fluid density stratification is defined as the relative density change in the upper (at 10 % depth) and lower (at 90 % depth) parts of the cargo tank. The hydrometer was used to measure density, allowing measurements in the range of 650 ... 1630 kg/m3 with an accuracy of 1 kg/m3 while controlling the temperature. Density measurements were taken at 6-hour intervals. It has been experimentally proved that during the 48-hour transportation of the drilling fluid with the density of 1295 kg/m3, the density value at the indicated depths is 1163 and 1524 kg/m3 respectively, while the density stratification reaches 31 %. It is offered to prevent the density stratification by creating a forced X-shaped circulation of the drilling fluid between cargo tanks which stand side by side. It is offered to regulate and maintain automatically the drilling fluid density in the range of 2 ... 7 % by using programmable controllers. When the density stratification reaches 7 %, the controller switches on the circulation pumps and circulates the drilling fluid between tanks which stand side by side. This increases the drilling fluid uniformity and helps to reduce the density stratification along the depth of the cargo tank. The process of additional circulation of the drilling fluid is rationally ensured until the density stratification reaches a value of 2 %. Fulfilment of the above-mentioned conditions will ensure that the drilling fluid maintains its operational properties and the energy consumption associated with the additional operation of the circulation pumps is minimised.

Direct Approach or Detour: A Comparative Model of Inhibition and Neural Ensemble Size in Behavior Selection

Organisms must cope with different risk/reward landscapes in their ecological niche. Hence, species have evolved behavior and cognitive processes to optimally balance approach and avoidance. Navigation through space, including taking detours, appears also to be an essential element of consciousness. Such processes allow organisms to negotiate predation risk and natural geometry that obstruct foraging. One aspect of this is the ability to inhibit a direct approach toward a reward. Using an adaptation of the well-known detour paradigm in comparative psychology, but in a virtual world, we simulate how different neural configurations of inhibitive processes can yield behavior that approximates characteristics of different species. Results from simulations may help elucidate how evolutionary adaptation can shape inhibitive processing in particular and behavioral selection in general. More specifically, results indicate that both the level of inhibition that an organism can exert and the size of neural populations dedicated to inhibition contribute to successful detour navigation. According to our results, both factors help to facilitate detour behavior, but the latter (i.e., larger neural populations) appears to specifically reduce behavioral variation.

A Categorization of Power Measurement and Power Consumption Models in the Telco Cloud

This article surveys the literature, over the period 2010-2020, on measurement of power consumption and relevant power models of virtual entities as they apply to the telco cloud. Hardware power meters are incapable of measuring power consumption of individual virtual entities co-hosted on a physical machine. Thus, software power meters are inevitable, yet their development is difficult. Indeed, there is no direct approach to measurement and, therefore, modeling through proxies of power consumption must be used. In this survey, we present trends, fallacies and pitfalls. Notably, we identify limitations of the widely-used linear models and the progression towards Artificial Intelligence / Machine Learning techniques as a means of dealing with the seven major dimensions of variability: workload type; computer virtualization agents; system architecture and resources; concurrent, co-hosted virtualized entities; approaches towards attribution of power consumption to virtual entities; frequency; and temperature.

System Calibration Including Time Delay Estimation for GNSS/INS-Assisted Pushbroom Scanners Onboard UAV Platforms

Unmanned aerial vehicles (UAVs ) equipped with imaging sensors and integrated global navigation satellite system/inertial navigation system (GNSS/INS ) units are used for numerous applications. Deriving reliable 3D coordinates from such UAVs is contingent on accurate geometric calibration, which encompasses the estimation of mounting parameters and synchronization errors. Through a rigorous impact analysis of such systematic errors, this article proposes a direct approach for spatial and temporal calibration (estimating system parameters through a bundle adjustment procedure) of a GNSS/INS -assisted pushbroom scanner onboard a UAV platform. The calibration results show that the horizontal and vertical accuracies are within the ground sampling distance of the sensor. Unlike for frame camera systems, this article also shows that the indirect approach is not a feasible solution for pushbroom scanners due to their limited ability for decoupling system parameters. This finding provides further support that the direct approach is recommended for spatial and temporal calibration of UAV pushbroom scanner systems.

Combined Coulomb and Viscous Damping Estimation Using Topological Signal Processing

In this work we develop a novel time-domain approach for the simultaneous estimation of the damping parameters for a single degree of freedom oscillator with both viscous and coulomb damping. Our approach leverages zero-dimensional sublevel set persistence — a tool from Topological Signal Processing (TSP) — to analyze the ring down vibration of the signal. Sublevel set persistence is used as it alleviates the need for peak selection when analyzing the time-domain of the signal and provides an alternative noise-robust method for visualizing the damping envelope. We are able to successfully estimate the damping parameters using both a direct approach and a function fitting method. We show that the direct approach is only appropriate for low levels of additive noise, but allows for a less computationally demanding estimation of the parameters. Alternatively, the function fitting method provides accurate estimates for significantly higher levels of additive noise. The results are provided through a numerically simulated example with mixed coulomb and viscous damping. We demonstrate the robustness of our method for accurately estimating both damping parameters for various levels of additive noise, a wide range of sampling frequencies, and both high and low levels of damping. This analysis includes providing suggested limitations of the method when applied to real-world signals.

PENINGKATAN KEMAMPUAN PENULISAN SURAT DINAS DI KECAMATAN PONTANG KABUPATEN SERANG, PROVINSI BANTEN

Socialization and training on writing official letters were held in Kubang Puji Village, Pontang District, Serang Regency, Banten Province. The activity was carried out as a result of the collaboration of a team of Indonesian language lecturers from several different departments at the Politeknik Negeri Jakarta to jointly go down to the community to carry out service in the form of socializing and training official letters for staff in the village and sub-district environment. This activity begins with socialization which aims to regenerate public awareness to be able to use the Indonesian language properly and correctly, both orally and in writing, as well as socialize matters related to correspondence material, especially official letters. After that, the lecturer team made a direct approach to the community to carry out technical guidance on writing official letters. The result of this activity is that the community is reminded of the importance of communicating using good and correct Indonesian, as well as increasing knowledge and skills in writing official letters. Keywords –socialization, training, official letter, Pontang District, Serang-Banten Abstrak Sosialisasi dan pelatihan penulisan surat dinas dilaksanakan di Desa Kubang Puji, Kecamatan Pontang, Kabupaten Serang, Provinsi Banten. Kegiatan tersebut dilaksanakan hasil kolaborasi di antara tim dosen bahasa Indonesia yang berasal dari beberapa jurusan yang berbeda di Politeknik Negeri Jakarta untuk sama-sama turun ke masyarakat untuk melakukan pengabdian berupa sosialisasi dan pelatihan surat dinas bagi para staf di lingkungan desa dan kecamatan. Kegiatan ini diawali dengan sosialisasi yang bertujuan untuk menumbuhkan kembali kesadaran masyarakat untuk dapat menggunakan bahasa Indonesia dengan baik dan benar, baik secara lisan maupun tertulis, serta menyosialisasikan juga hal-hal yang terkait dengan materi korespondensi, khususnya, surat dinas. Setelah itu, tim dosen melakukan pendekatan secara langsung dengan masyarakat untuk membimbing secara teknis dalam penulisan surat dinas. Hasil dari kegiatan ini masyarakat tersadarkan kembali akan pentingnya berkomuniasi menggunakan bahasa Indonesia yang baik dan benar, serta adanya peningkatan pengetahuan dan keterampilan dalam menulis surat dinas. Kata kunci –sosialisasi, pelatihan, surat dinas, Kecamatan Pontang, Serang-Banten