scholarly journals Physical and mechanical properties of subfossil oak (Quercus, sp.) wood

2010 ◽  
Vol 58 (4) ◽  
pp. 123-134 ◽  
Author(s):  
Tomáš Kolář ◽  
Michal Rybníček
Keyword(s):  
Mechanical Properties ◽  
Czech Republic ◽  
Radiocarbon Dating ◽  
Physical And Mechanical Properties ◽  
Wood Properties ◽  
The Other ◽  
The Czech Republic ◽  
Oak Wood ◽  
Gravel Pit ◽  
Subfossil Wood

The paper deals with the examination of physical and mechanical properties of subfossil wood of oak (Quercus, sp.). The issue of establishing physical and mechanical properties of subfossil oak wood has not yet been addressed in the area of the Czech Republic. The main objective is to find out what changes to subfossil wood properties have occurred in comparison with recent wood. For these purposes, samples from three locations were taken (gravel pit Tovačov – district Přerov, gravel pit Kostomlátky – district Nymburk, and the Bečva basin near Osek nad Bečvou). All of the selected properties were tested in compliance with relevant valid Czech technical norms (ČSN). The results provide us with a realistic picture of the properties of wood that has been deposited under the ground in very specific conditions for thousands of years. With regard to density, the results do not show any definite changes. The dimensions of subfossil wood are approximately doubled in comparison with recent wood. On the other hand, there is an obvious decrease in mechanical properties. The paper also offers the results of dendrochronological or radiocarbon dating of the trunks.

Testing and Optimization of Production of Technical Foam for the Production of Cement Foam

2018 ◽  
Vol 276 ◽  
pp. 254-258
Author(s):  
Karel Mikulica ◽  
Dušan Dolák
Keyword(s):  
Mechanical Properties ◽  
Czech Republic ◽  
Construction Industry ◽  
Building Materials ◽  
Cement Mortar ◽  
Physical And Mechanical Properties ◽  
Foam Concrete ◽  
The Czech Republic ◽  
Insulation Materials ◽  
The Many

In the current construction industry, great importance is given to the usage of thermally insulating building materials. One of the many such materials can be a cement foam or foam concrete, a mixture of cement mortar and technical foam. This material can be, due to its consistency right after mixing, applied to uneven horizontal surfaces where usage of conventional thermal board insulation materials would be complicated. This paper discusses the methodology of testing of the physical and mechanical properties of foaming additives such as strength, density, foaming number and half-separability of technical foams. Then this methodology was subsequently verified on the five commonly used foaming additives in the Czech Republic.

scholarly journals Dendrochronological and radiocarbon dating of subfossil wood from the Morava River basin

2011 ◽  
Vol 38 (2) ◽  
pp. 155-161 ◽  
Author(s):  
Tomáš Kolář ◽  
Michal Rybníček
Keyword(s):  
River Basin ◽  
Radiocarbon Dating ◽  
The Czech Republic ◽  
The Past ◽  
15Th Century ◽  
Gravel Pit ◽  
German Standard ◽  
Morava River ◽  
Subfossil Wood ◽  
Morava River Basin

Abstract The paper deals with dendrochronological and radiocarbon dating of subfossil trunks found in the basin of the Morava River. The research into subfossil trunks had been conducted in the Czech Republic in the past but the research stopped in 2001. 160 records of measurements of subfossil, predominantly oak trunk samples, are preserved from that time. Three years ago the research was reopened and again the most trunks were found in the basin of the Morava River. 92 samples of oak trunks and 7 samples of other tree species (poplar, elm, maple, beech) were taken from selected sites. The samples were processed in compliance with the standard dendrochronological methodology. To date the samples, Czech, Austrian, Polish and German standard chronologies were used. In cases when the dendrochronological dating was unsuccessful, the samples were sent for radiocarbon dating. In total, 35 samples were dated, mainly by the radiocarbon method. Subfossil trunks from gravel pit Tovačov were dated and classified into 4 different periods, the oldest being from 2780–2190 BC. In Osek nad Bečvou, the samples were taken from two sites. Whereas from the 4 trunks taken in the river channel each was from a different period, the trunks from the gravel pit come from 981–1015 AD. The trunks found in the Morava River basin near Strážnice were dated to the 10th–15th century. In the future, we expect to extend the amount of the acquired samples with the aim to create a link to the existing standard chronology or to create a long floating average treering curve.

Analysis of Alkali Oxides Influence on the Microstructure of Refractory Grog

2021 ◽  
Vol 325 ◽  
pp. 188-193
Author(s):  
Lenka Nevřivová ◽  
David Zemánek
Keyword(s):  
Mechanical Properties ◽  
Czech Republic ◽  
Experimental Work ◽  
Raw Materials ◽  
Physical And Mechanical Properties ◽  
Special Kind ◽  
Alumina Content ◽  
Refractory Materials ◽  
The Czech Republic ◽  
Alkali Oxides

The development and subsequent production of these special kind of grog from raw materials available in the Czech Republic is one of the possibilities how to reduce income costs for the production of refractory materials with specific properties. The experimental work is focused on verifying the possibility of producing grog with increased alumina content from available raw materials. The raw materials are kaolins and claystones. To achieve a higher content of alumina in the grog, waste mullite dust is used. In order to improve the physical and mechanical properties of the grog, modifiers are used. Selected modifiers are expected to affect positively on the resulting density while maintaining the heat properties.

Physical and Mechanical Properties of Tenun Pahang Fabrics using Alternative Yarns

2016 ◽  
Vol 13 (2) ◽  
pp. 67
Author(s):  
Engku Liyana Zafirah Engku Mohd Suhaimi ◽  
Jamil Salleh ◽  
Suzaini Abd Ghani ◽  
Mohamad Faizul Yahya ◽  
Mohd Rozi Ahmad
Keyword(s):  
Mechanical Properties ◽  
Physical And Mechanical Properties ◽  
The Other ◽  
Silk Fabrics ◽  
Recovery Angle ◽  
Made In

An investigation on the properties of Tenun Pahang fabric performances using alternative yarns was conducted. The studies were made in order to evaluate whether the Tenun Pahang fabric could be produced economically and at the same time maintain the fabric quality. Traditional Tenun Pahang fabric uses silk for both warp and weft. For this project, two alternative yarns were used which were bamboo and modal, which were a little lower in cost compared to silk. These yarns were woven with two variations, one with the yarns as weft only while maintaining the silk warp and the other with both warp and weft using the alternative yarns. Four (4) physical testings and three (3) mechanical testings conducted on the fabric samples. The fabric samples were evaluated including weight, thickness, thread density, crease recovery angle, stiffness and drapability. The results show that modal/silk and bamboo silk fabrics are comparable in terms of stiffness and drapability, hence they have the potential to replace 100% silk Tenun Pahang.

Anatomical, Chemical and Mechanical Properties of Fast-Growing Populus × Euramericana cv. ‘74/76’

IAWA Journal ◽  
2014 ◽  
Vol 35 (2) ◽  
pp. 158-169 ◽  
Author(s):  
Zhao Rongjun ◽  
Yao Chunli ◽  
Cheng Xianbao ◽  
Lu Jianxiong ◽  
Fei Benhua ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Sandy Loam ◽  
Physical And Mechanical Properties ◽  
Wood Properties ◽  
Planting Density ◽  
Dry Density ◽  
Growth Rings ◽  
Fast Growing ◽  
Breast Height ◽  
Large Growth

The anatomical characteristics, chemical composition, and physical and mechanical properties of fast-growing Populus × euramericana cv. ‘74/76’ juvenile wood were investigated. Four- to five-year-old clonal plantation trees were harvested from two different experimental sites in the suburbs of Beijing. The Shunyi site had black alkali soil with a planting density of 4 × 6 m and the Miyun site had sandy loam soil with a planting density of 3 × 5 m. The test results showed that the poplar trees from the two sites were both fast growing, with poplar at Shunyi growing faster than at Miyun. There were no significant differences in wood properties between trees grown at the two sites. Fiber length at breast height varied from 872 to 1300 μm between growth rings, average fiber width varied from 21.0 to 25.5 μm and double wall thickness varied from 5.0 to 6.6 μm. Average cellulose, lignin and hemicellulose contents in the samples were 48.9%, 25.4%, and 18.8%, respectively. MFA was higher in the first two growth rings (20–25°), and then decreased rapidly to 12° close to the bark. The average air-dry density at breast height was 401 kg/m3 while the average MOE at breast height was 9.3 GPa. The trees showed large growth rates in both height and stem diameter during the growing season. However, wood properties of the juvenile poplar appeared to be similar to those of poplars with a slower growth rate.

scholarly journals EFFECT OF THERMO-MECHANICAL TREATMENT ON PROPERTIES OF PARICA PLYWOODS (Schizolobium amazonicum Huber ex Ducke)

2017 ◽  
Vol 41 (1) ◽  
Author(s):  
Mírian de Almeida Costa ◽  
Cláudio Henrique Soares Del Menezzi
Keyword(s):  
Mechanical Properties ◽  
Mechanical Treatment ◽  
Physical And Mechanical Properties ◽  
The Other ◽  
Modulus Of Rupture ◽  
Thermal Treatments ◽  
Mechanical Compression ◽  
Specific Mass ◽  
Thermo Mechanical Treatment ◽  
Temperature And Pressure

ABSTRACT Thermo-mechanical treatment is a technique for wood modification in which samples are densified by means of heat and mechanical compression, applied perpendicularly to fibers, which under different combinations of time, temperature, and pressure increases wood density and thus improve some of its properties. This study aimed to treat thermo-mechanically parica plywood and observe the effects on its physical and mechanical properties. Specimens were submitted to two treatments, 120 and 150 ºC, remaining under pressure for seven minutes and, subsequently, under zero pressure for 15 minutes. Results showed a significant increase in specific mass from 0.48 g cm-3 to an average of 0.56 g cm-3, and a compression ratio of about 31.7% on average. Physical properties also varied significantly and results showed that treated samples swelled and absorbed more water than those untreated, leading to a greater thickness non-return rate. This indicates the proposed thermal treatments did not release the internal compressive stress generated during panel pressing, not improving its dimensional stability as a result. On the other hand, mechanical properties were positively affected, leading to an increase of 27.5% and 51.8% in modulus of rupture after treatments at 120 and 150 ºC, respectively. Modulus of elasticity and glue-line shear strength did not vary statistically and Janka hardness was 29.7% higher after treatment at 150 ºC.

scholarly journals Ground beetles (Carabidae) from slopes of Macošská stráň and Vilémovická stráň (Protected landscape area of Moravský kras, Czech Republic)

2011 ◽  
Vol 59 (3) ◽  
pp. 143-150 ◽  
Author(s):  
Jana Niedobová ◽  
Vladimír Hula ◽  
Pavla Šťastná
Keyword(s):  
Czech Republic ◽  
Endangered Species ◽  
Threatened Species ◽  
Ground Beetles ◽  
Red List ◽  
The Other ◽  
Pitfall Traps ◽  
The Czech Republic ◽  
Group A

Collecting of Carabidae was conducted using pitfall traps at four sites. The first two sites (T1 + T2) were at the slope of Macošská stráň and the other two sites (T3 + T4) at the slope of Vilémovická stráň. The study was done in 2008 and 2009. At Macošská stráň in 2008, 21 species of Carabidae with the total number of 228 individuals were found and in 2009, 18 species of the total number of 116 specimens were collected. At Vilémovická stráň in 2008, 22 species of Carabidae with the total number of 1977 specimens were found and in 2009, 21 species of the total number of 623 specimens were caught. In terms of classification of relictness, Macošská stráň in 2008 was dominated by species of adaptable group A (60%), species of eurytop group (E) were represented by 35% and of relic group (R) by 5%. In 2009, the same representation of species of groups A and E (47%) were found and the species of group R were represented by 6%. Vilémovická stráň in 2008 was dominated by species of group A (52%), species of group E were represented by 43% and of group R by 5%. In 2009 also dominated species of group A (54%), species of group E were represented by 41% and of group R by 5%. In the studied area we reported four endangered species of Carabidae protected by Law (No. 395/1992 Coll.) as amended, these were Calosoma auropunctatum (critically endangered), Brachinus crepitans, Carabus ullrichii and Cicindela campestris (endangered) and two species listed under the Red List of Threatened Species of the Czech Republic (Veselý et al., 2005). One of the species is listed as vulnerable (Calosoma auropunctatum) and one as near endangered (Carabus cancellatus). Another significant species found on the monitored sites was Aptinus bombarda.

scholarly journals Spiders of the Vine Plants in Southern Moravia

2015 ◽  
Vol 63 (5) ◽  
pp. 1471-1476
Author(s):  
Lucie Havlová ◽  
Vladimír Hula ◽  
Jana Niedobová
Keyword(s):  
Czech Republic ◽  
Soil Management ◽  
Common Species ◽  
Red List ◽  
The Other ◽  
Important Species ◽  
The Czech Republic ◽  
Spider Species ◽  
Southern Moravia ◽  
Different Parts

Araneofauna of vineyards is relatively known in Central Europe but we have a lack of knowledge about araneofauna which occur directly on the vine plants. Our investigation was focused on spiders which live on vine plants, especially on the vine plants trunks. We investigated spiders in six vineyards in southern Moravia (Šatov, Mikulov, Popice, Morkůvky, Nosislav and Blučina). Vineyards were under different soil management, traps were placed on different parts of particular locality (terraced and plain) and all localities were under integrated pest management. We employed two types of cardboard traps for spider collecting during whole vegetation season. Altogether, we collected 21 spider species which belong to seven families. The most important species was Marpissa nivoyi (Lucas, 1836), which is mentioned in the Red List as vulnerable (VU) and Sibianor tantulus (Simon, 1868) which had unknown distribution in the Czech Republic. The other very interesting result is that the most common species is myrmecomorph Synageles venator (Lucas, 1836), which is scarcely recorded in such huge numbers as we documented in our study.

Protistátní trestné činy v moderních kodifikacích

2021 ◽  
Author(s):  
David Kolumber
Keyword(s):  
Czech Republic ◽  
Soviet Union ◽  
Point Of View ◽  
The Other ◽  
The Czech Republic ◽  
Other Hand ◽  
Legal Concepts ◽  
Atlantic Area ◽  
Current Arrangement

The contribution “Anti-state Crimes in Modern Codifications” deals with the topic of anti-state crimes during centuries. Firstly, legal concepts in the pre-state period are mentioned. Then the attention is paid on the evolution of this institute in the Euro-Atlantic area. From this point of view, there are mentioned mainly regulations from England (1351), France (1810), Germany (1871) and Soviet Union (1958) which could be remarked as the most important for the development of other countries. On the other hand, it also reminds the development of codifications in Czechoslovakia, the Czech Republic and Slovakia, which were affected by the Austro-Hungarian legislations as well as German and Soviet approaches. The Czech current arrangement generally does not depart from the other European samples, but it cannot be omitted that in the Czech Republic it is distinguished the penal concept of the high treason (Landesverrat, vlastizrada) from the constitutional concept (Hochverrat, velezrada) which is dedicated to the presidential anti-state activities. The contribution also indicates that the concept of anti-state crimes in countries has not been unified and it has been varying according to various experiences and attitudes.

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