CALCULATION OF LOSSES OF ACTIVE POWER AND ENERGY IN TRANSMISSION LINES AND TRANSFORMERS, AS A PART OF THE ELECTRICAL DISTRIBUTION POWER NETWORK

The paper inhere discusses the impact of renewable distributed generation sources upon the power and energy losses in electrical distribution power networks where these sources are attached. In addition a set of mathematical expressions to calculate these active power and energy losses are presented with the respective examples and implementation

Prognostic factors for anastomotic insufficiency in elective colorectal surgery

Introduction: Anastomotic insufficiency is a severe, potentially fatal complication of colorectal surgery. Its frequency, according to different authors, reaches up to 20%. It is related to two main types of risk factors: associated with the patient and associated with the therapeutic approach.Aim: The aim of the study is to determine prognostic factors for anastomotic insufficiency. The collected data from patients operated on for a period of 5 years (2013-2017) in the Second Surgery Clinic, Alexandrovska University Hospital, Sofia, were analyzed.Materials and Methods: A total of 158 patients undergoing elective colorectal surgery have been retrospectively included. These on emergency, non-proven malignancies and with preoperative haemotransfusion were excluded from the study. All patients were evaluated by age, gender, BMI, ASA score, Charlson Comorbidity Score, localization, TNM stage and histological type. The surgical approach and the method of resection were determined. The postoperative period and complications were classified according to the Clavien-Dindo scale. The number of leukocytes, platelets, RDW, CRP and albumin were examined preoperatively, and on the day 1 and day 4, in the early postoperative period.Results: The average age of the patients was 67 (29-87). Of these, 100 (63.3%) were men, and 58 (36.7%) are women. The mean BMI was 27.1 (23-33). A total of  78.9% of the operated patients weree in TNM stage II and III. Histologically, 77.8% were moderately differentiated adenocarcinomas. The mean Charlson Comorbidity Score for the sample was 7.1 (range: 2-13), and the ASA score was 3 (2-4). The rectum was the most common localization - 40.1%, followed by right colon 22.8%, and the sigmoid colon 20.9%. Over the review period, most resections were conventional, with only 15.2% laparoscopic approach. The operations performed were right hemicolectomy - 36 (22.8%), left hemicolectomy -15 (9.5%), segmental resection - 38 (24.1%), total colectomy - 4 (2.5%) resection of the rectum - 44 (27.9%), and other - 21 (13.3%). In 12 (7.6 %) of the patients insufficiency was reported between day 2 and day 3, postoperatively. Five of them were treated conservatively and the other six were reoperated. Seven of the insufficiencies were after anterior resection of the rectum, 2 were after left hemicolectomy, 1 after resection of the sigmoid colon, one was after right hemicolectomy, which had been treated conservatively. The mean postoperative period of patients with insufficiency was 22 days (range: 9-45). For patients without complications, the postoperative period was 9.4 days (range: 4-21) and there was a strict statistical difference (P <0.05). All patients experienced an increase in leukocyte counts postoperatively, albumin drop, increased CRP and ESR. The mean platelet counts depended on the presence of insuffiency.Conclusion: The anterior resection, which is associated with technically more difficult anastomosis and neoadjuvant radiotherapy is a potential risk factor for anastomotic insufficiency. The use of blood parameters in the postoperative period allows early diagnosis of the complication and possible change of the therapeutic strategy

Approach for preliminary determination of the type and number of vertical rods in grounding installations

The paper inhere describes a new practical approach for fast preliminary onsite estimation of the number and the kind of vertical grounding rods as essential components of all grounding systems in electrical power facilities, networks and installations in industry, communal services, mining enterprises, etc

Natural Vegetation Recovery on Excavated Archaeological Sites: A Case Study of Ancient Burial Mounds in Bulgaria

As a distinctive component of the cultural landscape in Eurasia, burial mounds are well known for their historical value. Recently their role as biodiversity hotspots, especially in the homogenous agricultural landscape, has become particularly important. Archaeological excavations, although necessary, are destructive to the natural elements on the mounds. Restoration and vegetation recovery after such disturbances are needed for the preservation of biodiversity and for the cultural landscape integrity. In this study, we aimed to find out how effective is the natural vegetation recovery on the mounds after archaeological excavations. Successional stages between 2- and 30-years post-excavations have been studied. Vegetation sampling was performed on 15 mounds within 300 plots (1 × 1 m). Spontaneous succession was found to start immediately, and during the first decade, anthropophytes prevailed. In the subsequent years, their cover significantly decreased at the expense of species typical for the natural communities in the surroundings. Total species richness increased with the successional age and the vegetation composition became more similar to the semi-natural communities commonly established on mounds in Bulgaria. In the advanced successional stages, we registered a high rate of heterogeneity on the mounds, facilitated by the establishment of target plant species with different ecological requirements, including bryophytes. Provided the obtained results, we conclude that the natural vegetation recovery on the excavated and subsequently recovered mounds were very successful, and the current practice must continue in the future

First Survey of the Vascular and Cryptogam Flora on Bulgaria’s Ancient Mounds

This work represents the first study of the floristic diversity on Bulgaria’s ancient mounds. The objective of this research was to assess the importance of the mounds for the preservation of the native vascular and cryptogam flora. Our sampling design included 111 ancient mounds distributed throughout the country. We recorded a total of 1059 vascular plants, 58 bryophytes and 61 lichen taxa. Despite their small area, the mounds were shown to preserve nearly a quarter of the Bulgarian flora. The vegetation cover on the mounds included 61% perennials indicating a long-term persistence and stability. The majority (98%) of the established vascular plants were native species. Although the conservation significance of the vascular plant species were not common, we recorded 2 critically endangered, 9 endangered and 14 Balkan endemics during the present study. The lichen Arthopyrenia salicis was recorded for the first time in Bulgaria and a new locality of the rare bryophyte Ceratodon conicus was discovered. The established compositional difference between plots from the northern and southern slopes of the mounds (88.95%) is a testament to the high local habitat diversity. The prevalence of species characteristic for Festuco-Brometea suggests that the mounds preserve fragments of native grasslands and steppes. The variation in cover of agricultural and other human modified areas in the mounds’ immediate surroundings did not substantially affect their species richness. We argue that the ancient mounds should be taken into consideration in future green space planning

Balkan Vegetation Database: historical background, current status and future perspectives

The Balkan Vegetation Database (BVD; GIVD ID: EU-00-019; http://www.givd.info/ID/EU-00- 019) is a regional database that consists of phytosociological relevés from different vegetation types from six countries on the Balkan Peninsula (Albania, Bosnia and Herzegovina, Bulgaria, Kosovo, Montenegro and Serbia). Currently, it contains 9,580 relevés, and most of them (78%) are geo-referenced. The database includes digitized relevés from the literature (79%) and unpublished data (21%). Herein we present descriptive statistics about attributive relevé information. We developed rules that regulate governance of the database, data provision, types of data availability regimes, data requests and terms of use, authorships and relationships with other databases. The database offers an extensive overview about studies on the local, regional and SE European levels including information about flora, vegetation and habitats

Balkan Vegetation Database (BVD) – updated information and current status

The Balkan Vegetation Database (BVD; GIVD ID: EU-00-019) is a regional database, which was established in 2014. It comprises phytosociological relevés covering various vegetation types from nine countries of the Balkan Peninsula (Albania – 153 relevés, Bosnia and Herzegovina – 1715, Bulgaria – 12,282, Greece – 465, Croatia – 69, Kosovo – 493, Montenegro – 440, North Macedonia – 13 and Serbia – 2677). Currently, it contains 18,306 relevés (compared to 9.580 in 2016), and most of them (82.8%) are geo-referenced. The database includes both digitized relevés from the literature (65.6%) and unpublished data (34.5%). Plot size is available for 84.7% of all relevés. During the last four years some “header data information” was improved e.g. elevation (now available for 83.4% of all relevés), aspect (67.7%), slope (66%), total cover of vegetation (54.3%), cover of tree, shrub, herb, bryophyte and lichen layers (27.1%, 20.1%, 40.2%, 11.5% and 2.1%), respectively. Data access is either semi-restricted (65.6%) or restricted (34.4%). Most relevés (84.6%) are classified to syntaxa of different levels. The database has been used for numerous studies with various objectives from floristic, vegetation and habitat-related topics, to macroecological studies at the local, regional, national, continental and global levels. During the last four years, BVD data were requested from 111 different projects via the EVA and sPlot databases