خيارات البحث
النتائج 51 - 60 من 126
Investment costs optimization of multi-robot system using genetic algorithm
2012
Komasilovs, V., Latvia Univ. of Agriculture, Jelgava (Latvia)
Forethought deployment of an industrial production system is a significant step towards improving economic benefit of an industrial company. The author proposes the procedure for finding an optimal specification of multirobot system, which considers it on the level of components of the robotic system. Components are grouped into mobile or stationary units of the system. A set of agents is considered as a solution for particular mission, it defines a specification of a heterogeneous multi-robot system. The paper presents the concept of the optimization procedure and describes the implementation of investment costs optimization step, which uses genetic algorithm.
اظهر المزيد [+] اقل [-]Children with special needs family education as a partnership comprehension in rural area
2012
Kokle-Narbuta, I., Latvia Univ. of Agriculture, Jelgava (Latvia)
Family education as a support to families where children are with special needs is mentioned in family politics statements. Unfortunately, family education problems in rural areas characterise present day situation in Latvia. Professionals with less specific knowledge essential to deal with special needs satisfaction is a reality in rural areas in Latvia. It is vital to advance family autonomy, develop an opportunity to deal with consequences that disabilities cause and, improve environmental conditions for children with special needs. The aim of this article is to fortify necessity of family education as a partnership comprehension development to children with special needs in rural area. The investigation was carried out in National Rehabilitation centre ”Vaivari” in April 2012, by involving families with children with special needs. Analysis of scientific resources has been done; survey and statistical analysis of data were carried out, by using non-parametric method - Mann Whitney U test. During the research, the main family education comprehension aspects to families living in rural or city area and having children with special needs are identified. The advantages in special needs satisfaction context in rural areas and city environment are analysed. Measurements of respondent attitude to innovative family education e-solutions are made. Objectively and subjectively determined social isolation risk of families having children with special needs in rural area show the necessity to use family resources related to consequences that disabilities create. It is necessary to develop ways to use modern technological opportunities, provide appropriate family education and partnership with professionals.
اظهر المزيد [+] اقل [-]Individual tree identification using combined LIDAR data and optical imagery
2012
Prieditis, G., Latvia Univ. of Agriculture, Jelgava (Latvia) | Smits, I., Latvia Univ. of Agriculture, Jelgava (Latvia) | Dagis, S., Latvia Univ. of Agriculture, Jelgava (Latvia) | Dubrovskis, D., Latvia Univ. of Agriculture, Jelgava (Latvia)
The most important part in forest inventory based on remote sensing data is individual tree identification, because only when the tree is identified, we can try to determine its characteristic features. The objective of research was to explore remote sensing methods to determine individual tree position using LiDAR and digital aerial photography in Latvian forest conditions. The study site was a forest in the middle of Latvia – in Jelgava district (56º39’ N, 23º47’ E). Aerial photography camera (ADS 40) and laser scanner (ALS 50 II) were used to capture the data. LiDAR resolution was 9p m2 (500 m altitude). The image data is RGB, NIR and PAN spectrum with 20 cm pixel resolution. Image processing was made using Fourier transform, frequency filtering, and reverse Fourier transform. LiDAR data processing methods was based on canopy height model, Gaussian mask, and local maxima. Field measurements were tree coordinates, species, height, diameter at breast height, crown width and length. Using combined LiDAR and optical imagery data allows detecting at least 63% of all trees and about 85% of the dominant trees.
اظهر المزيد [+] اقل [-]Litter invertebrate communities in pine forests of different age (Baranivka area, Ukraine)
2012
Kalynovskyi, N., Zhytomyr National Agroecological Univ. (Ukraine)
Litter invertebrate communities in pine forests of different age (cut, six-year-old, 45-, 62-, and 105-year-old) in the Baranivka area of Zhytomyr Polissya (northwestern part of Ukraine) were studied. Samples were collected in April, August, and November 2011. 99% of extracted invertebrates were represented by mites (Acari) and springtails (Collembola). With forest age, the following tendencies were observed: mean absolute density of mites, springtails, and all litter-inhabiting animals increased; relative abundance of mites increased, but relative abundance of springtails decreased; taxonomic richness of invertebrate communities increased. In all samples, the most represented taxon was suborder Oribatida. The most diverse litter invertebrate community was in the 45-year-old forest. Similar compositions of invertebrate community were in the 45-, 62-, and 105-year-old forests as well as the cut and six-year-old ones.
اظهر المزيد [+] اقل [-]Distribution and status of common juniper (Juniperus communis L.) in Lithuanian pine stands
2012
Vaitkeviciute, R., Aleksandras Stulginskis Univ., Akademija, Kauno reg. (Lithuania)
Distribution and status of common juniper (Juniperus communis L.) in Lithuanian Pine stands are investigated in the study. The research was conducted in pure pine stands on sites with normal humidity and poor fertility in South – South Eastern parts of Lithuania. 40 stands were selected for data collection. Temporary rectangular sample plots with area of 10 square m were selected. According to method of underbrush evaluation, diameter root neck level, height and state index was measured for 3 juniper individuals located near the centre of sample plots. The number of sample plots depended on the area of each stand, but it was not lower than 10 in each stand. Average diameter of junipers was 3.03 cm, average height – 2.03 m. It was determined that average density of juniper individuals is 5055 individuals per hectare, and separately in vacciniosum and vaccinio – myrtilosum forest types - 4844 and 5282 individuals per hectare respectively. Average state index of juniper individuals in 6 grade scale was 2.96, which is near to grade 3 (slightly damaged). Results of the study show that distribution, status and dendrometric characteristics of junipers are different in adjacent regions of pine provenance.
اظهر المزيد [+] اقل [-]The assessment of vegetation diversity in black alder woodland key habitats in Zemgale [Latvia]
2012
Liepa, L., Latvia Univ. of Agriculture, Jelgava (Latvia) | Straupe, I., Latvia Univ. of Agriculture, Jelgava (Latvia
The article focuses on vegetation diversity in the black alder Alnus glutinosa (L.) Gaertn. woodland key habitats in Zemgale, Latvia. Together nine sample plots were established on these habitat types, where next stand South – South West (S-SW) side at the age 1-10; 20-30 and 40-50 years. The vegetation survey has been made in vegetation period of 2010 and 2011. Braun – Blanque method has been used to estimate the projective coverage (%) of tree layer (E3), shrub layer (E2), herb layer (E1) and moss layer (E0) in order to assess the edge effect impact on vegetation diversity according to different ages classes in a next stands of sample plots. The analysis of edge effect verifies that there is a significant influence from the edge in 1st and 3rd zones of sample plots, which lies at S-SW side at the ages 1-10 and 20-30. In sample plots several indicator species of black alder woodland key habitats have been found: Vaccinium myrtillus L., Lycopus europaeus L., Iris pseudacorus L., Comarum palustre L., Plagiomnium ellipticum (Brid.)T.kop. Ordination confirmed that composition of species are relatively close, which demonstrate that species are able to live in similar type growing conditions. Protective species Circaea lutetiana L. and Plagiothecium undulatum (Hedw.) B., S. et G were found on the study sites. Also, adventive species Impatiens parviflora DC was found. Comparing the analysis by zones and sample plots and different age classes, the impact on edge effect has been distinguished in black alder woodland key habitats.
اظهر المزيد [+] اقل [-]Thermal weed control in Norway spruce (Picea abies (L.) H.Karst.) nursery
2012
Silingiene, G., Aleksandras Stulginskis Univ., Akademija, Kauno reg. (Lithuania) | Vasinauskiene, R., Aleksandras Stulginskis Univ., Akademija, Kauno reg. (Lithuania) | Racinskas, J., Aleksandras Stulginskis Univ., Akademija, Kauno reg. (Lithuania)
Growing of economics and new technologies has caused the environment pollution and more intensive use of natural resources. The principles of stable and balanced forestry became more and more important. Ecologization forests economy directly and indirectly impacts environment, water, air, landscape. It is not allowed to use chemicals in ecological farms. In Lithuania the number of ecological farms is growing that is why the new effective ecological methods are needed to protect seedlings from weeds. Alternative to mechanical control of weed is to use high temperature. In ecological farms weed control after sowing time is pursued in mechanic, and recently in thermal way. In thermal weed control the surface of soil remains mechanically undisturbed, the roots of cultural plants remain undisturbed, too. These features are very important in forest nurseries, where different kinds of tree species are growing. Seedlings are very small at the beginning of growing, so mechanical weed control is difficult. Thermal weed control could be a good alternative. Comparable data of 2009-2011 thermal weed control research in Norway spruce (Picea abies (L.) H. Karst.) nursery is given. The efficiency of destroyed 16 weed sorts using thermal and mechanical ways of weed control is given. Thermal weed control for short age weeds is 20.3% more effective in comparison with mechanical way. Mechanical way is 35.2% more effective for perennial weeds. It was detected that in order to control weeds of different growth stages, it is necessary to use different treatment time of damp water stream.
اظهر المزيد [+] اقل [-]Below-ground biomass production in young stands of Scots pine (Pinus sylvestris L.) on abandoned agricultural land
2012
Bardulis, A., Latvia Univ. of Agriculture, Jelgava (Latvia);Latvian State Forest Research Inst. Silava, Salaspils (Latvia) | Jansons, A., Latvian State Forest Research Inst. Silava, Salaspils (Latvia) | Liepa, I., Latvia Univ. of Agriculture, Jelgava (Latvia)
Tree roots take up a high proportion of forest biomass, and nowadays we use different methods to estimate the root biomass. Methods vary greatly due to the different studies and different excavation methods used. In the summer 2010, a study of the below-ground biomass of young Scots pine Pinus sylvestris L. stands was carried out in central Latvia. In this paper, different below-ground biomass fractions data of 10 sample trees from the abandoned agricultural land plantations were approximated by allometric functions depending on tree stem diameter at breast height 1.3 m (DBH). The main objective was to determine the average below-ground biomass and approximated below-ground biomass fractions by allometric functions depending on tree DBH of young stands of Scots pine on abandoned agricultural land. Our regressions offer good overall approximations of the data. DBH – stump, coarse root and small root and total biomass regressions were highly significant (p is less than 0.001). The most substantial part of total below-ground biomass was from stumps (45%). The smallest shares of the biomass were coarse roots 38% and small roots 16%. The largest portion (52%) of the total fine-root biomass of 12- and 14-year-old Scots pine stands was located at a depth of 0–10 cm, decreasing in deeper mineral soil layers. Total dry (DM) below-ground biomass including fine-root biomass was 19.0 ±5.2 t DM ha-E1.
اظهر المزيد [+] اقل [-]Evaluation of forest regeneration results after stump extraction in Joint stock company ''Latvian State Forests''
2012
Zimelis, A., Latvia Univ. of Agriculture, Jelgava (Latvia);Latvian State Forest Research Inst. Silava, Salaspils (Latvia) | Lazdans, V., Latvian State Forest Research Inst. Silava, Salaspils (Latvia) | Lazdina, D., Latvian State Forest Research Inst. Silava, Salaspils (Latvia)
With the increase in demand for renewable energy resources, new studies are carried out about under - utilized resources, namely, stumps. To begin to use stumps in industrial application, it is necessary to find out stump extraction influence on the environment, biodiversity, forest regeneration and other important factors. In Zemgale forestry, Misas and Klīves forest districts managed by Joint stock company “Latvian State Forests” (LSF) study on stump extraction in woodlands where clear-cuttings done in 2006 was carried out in the block No. 177, compartments No. 1 and 5, as well as the block No. 176, compartments No. 3 and 9. In these territories two research objects were made where in November-December 2007 stump extraction as well as soil preparation were performed. Main tasks of the project were to evaluate the results of forest natural seeding and coppice ingrowths in natural regeneration areas and evaluate the use of different methods for artificial reforestation with spruce and pine containerized seedlings. It was observed that more seedlings were cut off in the areas where soil scarification with stump extractor was performed if compared to areas prepared with a disc trencher.
اظهر المزيد [+] اقل [-]Monitoring results of round wood utilization and wood processing sustainability in Latvia
2012
Krumins, J., Latvia Univ. of Agriculture, Jelgava (Latvia) | Smits, I., Latvia Univ. of Agriculture, Jelgava (Latvia) | Dagis, S., Latvia Univ. of Agriculture, Jelgava (Latvia) | Dubrovskis, D., Latvia Univ. of Agriculture, Jelgava (Latvia)
In society, discussions occasionally raise whether current level of wood cutting in Latvia is not too high to maintain sustainable forest industry and biodiversity. Cutting volumes for the state owned forests are calculated based on the model whose aim is to even the timber stock of each tree species in a long term period. The wood resource extraction in the private forests takes place according to free market conditions and depending on market prices. Therefore amount of round wood delivered from private forests can shift in a large range. The research had two main tasks. First task was to survey primary wood processing companies in Latvia and gather information about their round wood processing volumes, how their processing volumes divides between softwoods and hardwoods, dimensions of round wood companies demand for production and assortment of produced materials. Second task was to evaluate round wood utilization balance in the territory of Latvia and estimate if current use of timber resources in Latvia corresponds to amounts that are sustainable. Research results showed that consumption of softwood timber in Latvia is close to maximum to perform sustainable forestry, but consumption of hardwoods is possible to increase at least by 20–25%. Survey of primary wood processing companies showed that round wood processing volumes in Latvia vary from 6 to 7 million m3 annually and that large enterprises, which count only for 4% from total number of primary wood processing entities, process two thirds from annual round wood volume in country.
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