Skip to main content
Login | Suomeksi | På svenska | In English

Browsing by Subject "transmission"

Sort by: Order: Results:

  • Venkat, Vinaya (2021)
    The COVID-19 pandemic has brought into discussion the role of airborne transmission in infectious diseases. Many studies on enveloped viruses such as influenza suggest that respiratory viruses can be transmitted with large or small droplets formed when the patients talk, breathe, sneeze or cough. This comes under the category of direct contact. These droplets may also be transmitted indirectly as fomites through contact with contaminated surfaces. It has been difficult to prove that aerosols' transmission as the methods to capture virus in the air are not very sensitive. SARS-CoV-2 is a novel coronavirus affecting millions of people since 2019, and it has been challenging to contain the spread of this virus. Hence it is of vital importance to understand the transmission of the virus through aerosol and droplets. In this study, aerosol samples were collected from patients in the Surgical Hospital in Helsinki and patients at home in quarantine using various bioaerosols sampling devices like Biospot, Dekati, Button, and Andersen samplers, and passive sampling techniques to capture aerosols and droplets in the air. Such samples were subjected to cell culture on TMPRSS2 expressing Vero E6 cells to check for infectious viruses and RT-PCR using the N-gene targeting method to detect the presence of SARS-CoV-2 RNA in the samples. Out of the 32 saliva samples collected, 19 samples were tested positive by RT-PCR, but cell culture was not always positive. Bioaerosol samples collected using Dekati, Button, and Biospot samplers were negative by PCR. However, Andersen samplers showed positive results along with various passive aerosol samples collected on MEM, indicating aerosols' production of small sizes that can be transmitted air in the air to far distances and settling due to gravity. A relation between saliva samples and symptom days indicates the decrease in saliva viruses' infectivity with the prolonged infection as seen from the RT-PCR. From these findings, it can be concluded that SARS-CoV-2 can be spread by airborne and fomite transmission, and more so by patients with symptoms day 2-7 who are proven to be more infectious. Additionally, it was inferred that the Six Stage Andersen impactor would be the most efficient for aerosol sampling. Further studies are still needed to understand the characteristics of the spread and extent of infection caused by the variants of SARS-CoV-2.
  • Teinilä, Timo (2009)
    The history of tractor in Finland is 100 years old and in the whole world 120 years old. Development of tractors is continually ongoing. During the first decades it concentrated on engines. The introduction of air-filled tyres made it possible to increase speed on the road, which in turn lead to an increase in the number of gears. Most of the inventions within transmissions were made during the 1950s. The first powershift gears, stepless hydrostatic transmissions, fuell-sell tractor, range-gear and the power shuttle were all introduced during this time. Over the next decades these features were improved and presented as new inventions. The hydrostatic-mechanical power split continuously variable transmission (CVT) has become more common in recent years, but the basic invention was already in use elsewhere during the 1910s. The first CVT tractor was the Fendt 926, which was launched in 1995. Later introductions came in 1999, when ZF’s Eccom and the S-Matic both came to the market. Of all the CVT tractors that were introduced to the market up until 2008, only the John Deere IVT ant the Valtra Direct machines were equipped with the manufacturer’s own diesel engines and CVT transmissions. All other CVT tractors were manufactured using five different transmissions and engines. In the coming years, several more transmissions and brands will appear on the market. Mechanical Torotraks and steel belt variators will be available for low-horsepower tractors in the sub-75 kW class. At the same time the number of brands seen in the CVT arena is increasing and the differences in the construction of stepless transmissions will grow. Current CVT transmissions differ from each greatly, with different functional principles, functionality and structure. Transmissions are divided into two main categories on the basis on functional principle, either summing up torque or summing up speed. The functionality division in mostly based on the hydrostatic part. In a full-CVT transmission, the percentage decrease of hydrostatic transmission has s linear relationship with the percentage increase in running speed. The function of the hydrostat in a semi-CVT transmission in to balance the speed differences between different gearing rations. In these transmissions the hydrostatic part of the transmission in around 20–40%. The percentage of hydrostatic transmission in double-CVT transmission varies with the driving speed. Double-CVT transmissions can have several driving speeds where the percentage of mechanical transmission is very close to 100%. The theoretical predictions about how common new features will become is based upon a study of four-wheel tractors in Western Europe and Finland. This can be precisely calculated using Logistic-funktion the result would be better if the source data covered a longer time period. The regular S-curve depicts how common the new features will become in tractors of the future. The real growth area is during the period when the market share of 4wd tractors increase from 10 to 90 %. This shows that the annual growth in Western Europe was 4,0% and in Finland 7,5%. Within the next few years it will become necessary to study further new entrants of the CVT transmission market and to make predictions more precise by means of increasing the amount of source data. The users driving with conventional transmissions could utilise the driving strategies of CVT transmissions. Tractor manufacturers should ensure that their customers are fully educated in the use of their new machines, in order that they develop the correct driving habits. This in an important part of postmarketing strategy.