Jiří Dvořák

Jiří Dvořák

orcid

Research Focus & Metrics

Academic Career Length

8Years (2019-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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12 October 2021 in Forests
Verified
Journal Article
Open access
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MJMartin Jankovský
Martin Jankovský
SJSandra Paola Garcia Jacome
Sandra Paola Garcia Jacome
Jiří DvořákJiří Dvořák
Jiří Dvořák
Isaac NyarkoIsaac Nyarko
Isaac Nyarko
MHMiroslav Hajek
Miroslav Hajek
Innovations are a key component of the forest bioeconomy. Many types of innovations are needed for an efficient forest bioeconomy to be deployed. This article aimed to analyze the scientific literature on the topic of innovations in the forest bioeconomy, to understand where we are and where we are likely to be in the future, considering technologies, business models, etc. First, the scientific literature, in the form of peer-reviewed articles indexed in the Web of Science, was compiled in a comprehensive dataset, on which we analyzed the most important authors, their affiliations, regions they come from, journals where papers were most commonly published, and under which categories the papers were indexed. The total number of papers matching the keywords was 161. We found that the number of papers published on the topic is increasing and that, on average, each paper was cited 18 times. A total of 504 authors dealt with the topic, presenting a rather small community. This finding was reinforced by the outcomes of the analysis of regions where the authors of the papers were affiliated—Europe being the region to which most papers were affiliated. We conducted a qualitative synthesis of the literature on forest bioeconomy innovations. We found that authors dealt with the necessary adaptation of policies, while innovations were mainly focused on biorefining, biotechnology, production of various biomaterials, as well as innovations of business models and stakeholder interactions.

10 November 2023 in Croatian journal of forest engineering
Verified
Journal Article
Open access
Kalle KärhäKalle Kärhä
Kalle Kärhä
MSMilla Seuri
Milla Seuri
ABAllan Bradley
Allan Bradley
DRDominik Roser
Dominik Roser
CPCristian Pinto
Cristian Pinto
TKTihomir Krumov
Tihomir Krumov
The aim of the study was to provide a comprehensive overview of global long-distance road transportation of industrial roundwood. The study focused on the maximum gross vehicle weight (GVW) limits allowed with different timber truck configurations, typical payloads in timber trucking, the road transportation share of the total industrial roundwood long-distance transportation volume, and the average long-distance transportation distances and costs of industrial roundwood. The study was carried out as a questionnaire survey. The questionnaire was sent to timber transportation logistics experts and research scientists in the 30 countries with the largest industrial roundwood removals in Europe, as well as selected major forestry countries in the world (Argentina, Australia, Brazil, Canada, Chile, China, Japan, New Zealand, South Africa, Türkiye, the United States of America and Uruguay) in February 2022, and closed in May 2022. A total of 31 countries took part in the survey. The survey illustrated that timber trucking was the main long-distance transportation method of industrial roundwood in almost every country surveyed. Road transportation averaged 89% of the total industrial roundwood long-distance transportation volume. Timber truck configurations of 4 to 9 axles with GVW limits of around 30 tonnes to over 70 tonnes were most commonly used. The results indicated that higher GVW limits allowed significantly higher payloads in timber trucking, with the lowest payloads at less than 25 tonnes, and the highest payloads more than 45 tonnes. The average road transportation distance with industrial roundwood was 128 km, and the average long-distance transportation cost in timber trucking was €11.1 per tonne of timber transported. In the entire survey material, there was a direct relationship between transportation distance and transportation costs and an inverse relationship between maximum GVW limits and transportation costs. Consequently, in order to reduce transportation costs, it is essential to maximise payloads (within legal limits) and minimise haul distances. Several measures to increase cost- and energy-efficiency, and to reduce greenhouse gas emissions in road transportation logistics, are discussed in the paper. On the basis of the survey, it is recommended that up-to-date statistical data and novel research studies on the long-distance transportation of industrial roundwood be conducted in some countries in the future.

14 January 2021 in Croatian journal of forest engineering
Verified
Journal Article
Open access
MKMariusz Kormanek
Mariusz Kormanek
Jiří DvořákJiří Dvořák
Jiří Dvořák
Ground contact pressures exerted by elements of the machine chassis on the ground in the forest are associated with the machine impact on the soil during its operation. In the case of a crawler system, determining the ground contact pressure appears simple, which is not entirely true. The aim of the study was to analyze the loads on the ground (forest soil) exerted by the MHT 8002HV crawler harvester chassis. The measurements were made in Forest School Enterprise in Kostelec nad Černými Lesy, Central Bohemia Region in the Czech Republic, on brown soil made of clay on stony formations, fresh mixed mountain forest (FMMF), with the use of a hydraulic scale when extending the harvester crane forward along and perpendicular to the longitudinal axis of the machine. The calculations were carried out with a simulated load of the crane on the tree in question, assuming that the impact on the ground of the crawler system is heterogeneous and that the point impact comes from the crawler support wheels. As it was shown, the average ground contact pressures under the crawler track of the analyzed harvester generally do not exceed 70 kPa. The crane extension with a simulated load, which would have caused the crawler track to act on the ground with an average pressure exceeding 70 kPa, was limited by machine stability. On the other hand, high ground contact pressures may occur under a more loaded section of the crawler track if the active length of the crawler track is shortened. As it was shown in the case of a weak track tension, the course of ground contact pressures exerted on the soil deviates from the assumed usually homogeneous impact over the entire length of the crawler.

30 April 2019 in Forests
Verified
Journal Article
Open access
RLRadim Löwe
Radim Löwe
MSMonika Sedmíková
Monika Sedmíková
PNPavel Natov
Pavel Natov
MJMartin Jankovský
Martin Jankovský
PHPavla Hejcmanová
Pavla Hejcmanová
Jiří DvořákJiří Dvořák
Jiří Dvořák
Timber is the most important source of revenue in forestry and, therefore, is necessary to precisely estimate its volume. The share of timber volume produced by harvesters is annually growing in many European countries. Suitable settings of harvesters will allow us to achieve the most accurate volume estimates of the produced timber. In this study, we compared the different methods of log volume estimation applied by control and information systems of harvesters. The aim was to analyze the price categories that can be set up in the StanForD standard and to determine the differences between the algorithms used for log volume estimations. We obtained the data from *.STM files collected from March 2017 until June 2018 on a medium-size harvester. We analyzed price categories and found seven different algorithms used to estimate the log volumes. Log volume estimates according to Algorithm A2 were considered as standard because these estimates should be closest to the true log volumes. Significant differences, except the difference between Algorithm A2 and Algorithm A3, were found between log volumes estimated by different algorithms. After categorization of logs to assortments, the results showed that significant differences existed between algorithms in each assortment. In the roundwood assortment, which contains the most valuable logs, a difference of more than 6% was found between the log volumes estimated by Algorithm A5 and Algorithm A2. This is interesting because Algorithm A5 is widely used in some Central European countries. To obtain volumes closest to the true volumes, we should use Algorithm A2 for the harvester production outputs. The resulting differences between the algorithms can be used to estimate the volume difference between harvester outputs using the different price categories. Understanding this setting of harvesters and the differences between the price categories will provide users useful information in applied forest management.

4 April 2021 in Forests
Verified
Journal Article
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Jiří DvořákJiří Dvořák
Jiří Dvořák
MJMartin Jankovský
Martin Jankovský
MCMartin Chytrý
Martin Chytrý
Ondřej NuhlíčekOndřej Nuhlíček
Ondřej Nuhlíček
PNPavel Natov
Pavel Natov
RLRadim Löwe
Radim Löwe
Cut-to-length (CTL) operations are expanding in Central European bio-economies. However, they are costly, so efficiency must be maximized. The objective of this study was to analyze direct operational costs of three forwarders from the year 2006 until 2019. Annual amortization, services, materials, and personnel costs were analyzed and compared through ANOVA, trends were analyzed through linear regression. Forwarders LVS 5, John Deere 1010, and John Deere 1110E were deployed in coniferous forest stands with a mean stem volume between 0.10 and 0.84 m3/stem, forwarding distance between 261 and 560 m. The machines forwarded between 4045 and 34,604 m3 of timber per year, over operational times between 490 and 3896 MH (machine hours)/year, reaching machine utilization between 58% and 89%, machine productivity between 3.5 and 12.3 m3/MH, and costs between 20.95 and 84.39 €/MH. The most substantial were personnel costs (35 to 66% of the total costs), followed by materials (14.9–27.1%), amortization (12.5–15.7%), and services (3.3–22.1%). Differences between total operational costs per m3 of machines with different engine powers were not observed.

2 June 2020 in Forests
Verified
Journal Article
Open access
PDF file
MSMonika Sedmíková
Monika Sedmíková
RLRadim Löwe
Radim Löwe
MJMartin Jankovský
Martin Jankovský
PNPavel Natov
Pavel Natov
RLRostislav Linda
Rostislav Linda
Jiří DvořákJiří Dvořák
Jiří Dvořák
Harvesters produce one third of timber in Czechia. The aim of this study was to analyze the over- and under-bark volume estimates of Scots pine (Pinus sylvestris L.) timber produced by a mid-performance harvester. The data were collected between March 2017 and June 2018. In total, 4661 stems cut into 29,834 logs were analyzed. For volume estimation, StanForD offers several price categories using various algorithms. Three of these price categories are relevant for Czech forestry—M3s, M3toDE, and M3miDE. The M3s price category is based on the estimation of partial volumes of 10 cm long sections, which are summed. Therefore, this price category represents the volume estimation closest to the true volume. By comparison, the M3toDE and M3miDE price categories use the same algorithm for volume estimation, which is based on the Huber formula using a midspan diameter rounded down to the nearest whole centimeter. The M3toDE price category underestimated the over-bark volume by 6.48% compared to the reference price category M3s. The mean log volume estimated through the M3s price category was significantly higher than the M3toDE volume both in individual grades and without grading. We found significant differences between under-bark volume estimates by the diameter band bark deduction method (DBM) and the parametric linear bark deduction method (PLM) used in harvester’s systems according to the Guidelines for Electronic Scaling of Timber for Harvesters in Czechia (GEH) for Scots pine butt logs with rough bark, and also for other logs with normal bark thickness. To obtain under-bark volume estimates of Scots pine timber that are comparable with the Guidelines for Timber Scaling in Czechia (GTS) using the parametric nonlinear bark deduction method (PNM), we recommend using the algorithm of the M3toDE price category, with double bark thickness determined by the diameter band bark deduction method.