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Zeitschriftendaten
Format
Zeitschrift
eISSN
2255-8896
Erstveröffentlichung
18 Mar 2008
Erscheinungsweise
6 Hefte pro Jahr
Sprachen
Englisch

Suche

Volumen 59 (2022): Heft 3 (June 2022)

Zeitschriftendaten
Format
Zeitschrift
eISSN
2255-8896
Erstveröffentlichung
18 Mar 2008
Erscheinungsweise
6 Hefte pro Jahr
Sprachen
Englisch

Suche

6 Artikel
Uneingeschränkter Zugang

Multifocal Near-Eye Display: Timing of Optical Diffuser Elements and Synchronization to DLP-Based Projection Microunit

Online veröffentlicht: 23 Jun 2022
Seitenbereich: 106 - 115

Zusammenfassung

Abstract

The paper present the key technical details of a multifocal near-eye display concept. Along with an overview of the basic architecture, a particular implementation that utilises a digital light processing (DLP®) based spatial light modulator as the image source is provided in the study. The investigated approach involves the utilisation of a small-scale volumetric screen formed by a stack of fast-switching optical diffuser elements based on liquid crystal technology. The volumetric screen is illuminated by a rear image projector. To make the whole system functional and small, the challenge lies within the development of integrated control board for the projection modules as well as the synchronization of the DLP® projector image output to the optical diffuser element switching-cycle.

The main difficulty of the development process is accounting for the peculiarities of in-house developed diffuser elements and the off-the-shelf DLP®, which is the main focus of this paper. There is no direct control over the full set of DLP® operational parameters, an indirect method for adjusting frame dead time is proposed, showing that an increase in dead time close to 0.3 ms (from 0.3 ms to 0.6 ms in the particular setup) can be achieved without significantly sacrificing image colour depth or quality. Tuneable dead time mitigates the limitations set by the non-instantaneous switching of liquid crystal diffuser elements as longer dead times allow for the removal of image bleeding between frames.

Schlüsselwörter

  • Digital light processing
  • digital micromirror device
  • liquid crystal diffuser
  • multifocal display
  • near-eye display
Uneingeschränkter Zugang

Scenario-Based Modelling of Residential Sector Consumption: A Case Study in Latvia

Online veröffentlicht: 23 Jun 2022
Seitenbereich: 116 - 127

Zusammenfassung

Abstract

Promoting the development of energy communities is one of the planned development areas mentioned in the Latvian National Energy and Climate Plan (NECP). Even though energy communities do not yet exist in Latvia, they could improve the quality of the environment and stimulate the local economy. In any case, it is expected that the structure of household energy consumption in Latvia will change as households start to adopt new technologies such as electric cars and heat pumps, as well as participate in energy production and demand response.

Often the starting point for the development of an energy community is the geographic location of consumers. Therefore, for this study, a microdistrict was chosen in one of the most developed suburbs of Riga in Latvia, in which 76 households are located. The study identified five milestones on the path from mere neighborhood to the energy community. The resLoadSIM Residential Load Simulation tool was chosen to simulate realistic energy consumption with a 1-minute time resolution, as well as to model the future solar energy consumption and generation in the community on its way to becoming an energy community and meeting these goals. The network constraints associated with the transformer and lines are taken into account and it is assumed that the district will not invest in the development and expansion of the network.

Based on the results of the modelling, an analysis was made of the impact of the development of the energy community in Latvia and how each stage of development will affect energy consumption, the amount of renewable energy, the energy sent to the grid, the power consumed directly, and the share of solar energy in energy consumption.

Schlüsselwörter

  • energy community development
  • scenario-based modelling
  • resLoadSIM
  • RES
Uneingeschränkter Zugang

Development of the District Heating System on the Left Bank of the Daugava River in Riga

Online veröffentlicht: 23 Jun 2022
Seitenbereich: 128 - 139

Zusammenfassung

Abstract

In Latvia, heat supply is provided in three different ways: using district heating (hereinafter – DH), local heating and individual heating systems. Heat energy consumption consists of heat energy consumption for heating, hot water and heat energy technological processes. The structure of DH consumers has not changed in recent years and the largest consumers of heat are households 70 % of the total energy consumption. The district heating system accounts for approximately 29 % of the total consumption. There is also the so-called tertiary sector, which is made of municipal and state buildings with a minor total heat consumption of about 1 %.

It should be noted that 6570 % of energy is used for heating needs, and 3035% for hot water preparation. In Latvia, heat of DH consumers is produced both in boiler houses (hereinafter – BHs) and cogeneration plants (hereinafter – CHPs). The latter also produce electricity. Over the past 10 years, the distribution of heat produced in BHs and CHPs has changed significantly. The heat supply of the Latvian energy sector is a system consisting of three main elements heat source, transmission and distribution networks, and end consumer. Low efficiency of heat supply system elements creates risks to security of heat supply, resource sustainability and competitiveness. Increasing energy efficiency in the system as a whole, or in individual elements of the system, will promote the enhancement of the heat supply sector, while promoting economic growth as well. The research attempts to evaluate the energy efficiency of DH systems in the so-called left bank (hereinafter – LB) DH area (located on the left bank of the Daugava River in Riga).

Schlüsselwörter

  • District heating
  • heat sources
  • heat supply systems
  • left bank of the Daugava River in Riga
  • weather conditions
Uneingeschränkter Zugang

On the Issue of Collision of Balls in an Auto-Balancing Device

Online veröffentlicht: 23 Jun 2022
Seitenbereich: 140 - 154

Zusammenfassung

Abstract

The paper considers a model of a vertical double pendulum, which includes two balls suspended on rigid non-deformable threads to one centre of the suspension. For the proposed system of pendulums, differential equations of motion and conditions for collision of balls have been recorded. When simulating the motion of the pendulums, the central collision of the balls has been considered for various options of the motion of the suspension point: the suspension point is motionless; the suspension point oscillates in the vertical direction; the suspension point makes rotational motions in the vertical plane. Meanwhile, various conditions for the central collision between the balls have been considered: a perfectly inelastic collision; a perfectly elastic collision; a collision with transformation of collision energy (partially elastic collision). The results of numerical simulation are consistent with the behaviour of pendulums in real physical models, which makes it possible to simulate an elastic collision between balls when studying their acceleration in auto-balancing devices.

Schlüsselwörter

  • Balls
  • centre of suspension
  • elastic collision
  • equations of motion
  • pendulum
Uneingeschränkter Zugang

Specifics of Power Losses in Power Lines Including Parallel Lines

Online veröffentlicht: 23 Jun 2022
Seitenbereich: 155 - 169

Zusammenfassung

Abstract

Reducing power losses is invested in the trend of combating climate warming. It is necessary to know what parameters of power transmission lines affect the losses in them. In short and medium lines with accounted lumped parameters, the role and influence of the line parameters on losses are visible. In the lines with distributed parameters, at least with one series parameter and one parallel parameter, the role played by them, computing losses in ordinary way as difference between power at line sending and receiving end, is hidden. This is pronounced when considering parallel lines. In two parallel lines the losses can be greater than in a single line. This may occur when the current at the end of the lines is less than the boundary value: the value when two parallel lines and a single line have the same losses. The longer the line and the higher the rated voltage, the stronger the effect. In view of this aspect, it is necessary to know the boundary current. This current can be determined in ordinary way by a series of calculations changing the load value. In some cases, boundary current is affected not only by modulus of the current at the end of the line but also by its angle. It is better to calculate the boundary current by a formula, while studying the role of each parameter.

Schlüsselwörter

  • Distributed parameters
  • long lines
  • losses of power lines
  • medium lines
  • parallel power lines
Uneingeschränkter Zugang

Technological Assurance of Ti-6Al-4V Parts Produced by Additive Manufacturing Using Selective Metal Laser Sintering

Online veröffentlicht: 23 Jun 2022
Seitenbereich: 170 - 179

Zusammenfassung

Abstract

The research relates to a technological assurance of Ti6-Al-4V parts produced by additive manufacturing (AM) by means of a metal laser sintering, especially by a fibre laser 3D printer. The influence of technological parameters such as layer thickness, hatch spacing, laser travel speed and laser power have been analysed as well as the influence of thermal treatment as a post processing method has been studied. Technological parameters in combination with a thermal treatment present a challenge in order to manufacture satisfactory products in terms of mechanical properties. The research guides through different phases of experiments to distinguish the best technological parameters. The following research may be used for further investigation of technological assurance for additive manufacturable parts as well as forms the springboard for further research in development of new titanium composites using additive manufacturing methods.

Schlüsselwörter

  • 3D printing
  • additive manufacturing
  • grade 5
  • tensile strength
  • titanium
  • Ti-6Al-4V
6 Artikel
Uneingeschränkter Zugang

Multifocal Near-Eye Display: Timing of Optical Diffuser Elements and Synchronization to DLP-Based Projection Microunit

Online veröffentlicht: 23 Jun 2022
Seitenbereich: 106 - 115

Zusammenfassung

Abstract

The paper present the key technical details of a multifocal near-eye display concept. Along with an overview of the basic architecture, a particular implementation that utilises a digital light processing (DLP®) based spatial light modulator as the image source is provided in the study. The investigated approach involves the utilisation of a small-scale volumetric screen formed by a stack of fast-switching optical diffuser elements based on liquid crystal technology. The volumetric screen is illuminated by a rear image projector. To make the whole system functional and small, the challenge lies within the development of integrated control board for the projection modules as well as the synchronization of the DLP® projector image output to the optical diffuser element switching-cycle.

The main difficulty of the development process is accounting for the peculiarities of in-house developed diffuser elements and the off-the-shelf DLP®, which is the main focus of this paper. There is no direct control over the full set of DLP® operational parameters, an indirect method for adjusting frame dead time is proposed, showing that an increase in dead time close to 0.3 ms (from 0.3 ms to 0.6 ms in the particular setup) can be achieved without significantly sacrificing image colour depth or quality. Tuneable dead time mitigates the limitations set by the non-instantaneous switching of liquid crystal diffuser elements as longer dead times allow for the removal of image bleeding between frames.

Schlüsselwörter

  • Digital light processing
  • digital micromirror device
  • liquid crystal diffuser
  • multifocal display
  • near-eye display
Uneingeschränkter Zugang

Scenario-Based Modelling of Residential Sector Consumption: A Case Study in Latvia

Online veröffentlicht: 23 Jun 2022
Seitenbereich: 116 - 127

Zusammenfassung

Abstract

Promoting the development of energy communities is one of the planned development areas mentioned in the Latvian National Energy and Climate Plan (NECP). Even though energy communities do not yet exist in Latvia, they could improve the quality of the environment and stimulate the local economy. In any case, it is expected that the structure of household energy consumption in Latvia will change as households start to adopt new technologies such as electric cars and heat pumps, as well as participate in energy production and demand response.

Often the starting point for the development of an energy community is the geographic location of consumers. Therefore, for this study, a microdistrict was chosen in one of the most developed suburbs of Riga in Latvia, in which 76 households are located. The study identified five milestones on the path from mere neighborhood to the energy community. The resLoadSIM Residential Load Simulation tool was chosen to simulate realistic energy consumption with a 1-minute time resolution, as well as to model the future solar energy consumption and generation in the community on its way to becoming an energy community and meeting these goals. The network constraints associated with the transformer and lines are taken into account and it is assumed that the district will not invest in the development and expansion of the network.

Based on the results of the modelling, an analysis was made of the impact of the development of the energy community in Latvia and how each stage of development will affect energy consumption, the amount of renewable energy, the energy sent to the grid, the power consumed directly, and the share of solar energy in energy consumption.

Schlüsselwörter

  • energy community development
  • scenario-based modelling
  • resLoadSIM
  • RES
Uneingeschränkter Zugang

Development of the District Heating System on the Left Bank of the Daugava River in Riga

Online veröffentlicht: 23 Jun 2022
Seitenbereich: 128 - 139

Zusammenfassung

Abstract

In Latvia, heat supply is provided in three different ways: using district heating (hereinafter – DH), local heating and individual heating systems. Heat energy consumption consists of heat energy consumption for heating, hot water and heat energy technological processes. The structure of DH consumers has not changed in recent years and the largest consumers of heat are households 70 % of the total energy consumption. The district heating system accounts for approximately 29 % of the total consumption. There is also the so-called tertiary sector, which is made of municipal and state buildings with a minor total heat consumption of about 1 %.

It should be noted that 6570 % of energy is used for heating needs, and 3035% for hot water preparation. In Latvia, heat of DH consumers is produced both in boiler houses (hereinafter – BHs) and cogeneration plants (hereinafter – CHPs). The latter also produce electricity. Over the past 10 years, the distribution of heat produced in BHs and CHPs has changed significantly. The heat supply of the Latvian energy sector is a system consisting of three main elements heat source, transmission and distribution networks, and end consumer. Low efficiency of heat supply system elements creates risks to security of heat supply, resource sustainability and competitiveness. Increasing energy efficiency in the system as a whole, or in individual elements of the system, will promote the enhancement of the heat supply sector, while promoting economic growth as well. The research attempts to evaluate the energy efficiency of DH systems in the so-called left bank (hereinafter – LB) DH area (located on the left bank of the Daugava River in Riga).

Schlüsselwörter

  • District heating
  • heat sources
  • heat supply systems
  • left bank of the Daugava River in Riga
  • weather conditions
Uneingeschränkter Zugang

On the Issue of Collision of Balls in an Auto-Balancing Device

Online veröffentlicht: 23 Jun 2022
Seitenbereich: 140 - 154

Zusammenfassung

Abstract

The paper considers a model of a vertical double pendulum, which includes two balls suspended on rigid non-deformable threads to one centre of the suspension. For the proposed system of pendulums, differential equations of motion and conditions for collision of balls have been recorded. When simulating the motion of the pendulums, the central collision of the balls has been considered for various options of the motion of the suspension point: the suspension point is motionless; the suspension point oscillates in the vertical direction; the suspension point makes rotational motions in the vertical plane. Meanwhile, various conditions for the central collision between the balls have been considered: a perfectly inelastic collision; a perfectly elastic collision; a collision with transformation of collision energy (partially elastic collision). The results of numerical simulation are consistent with the behaviour of pendulums in real physical models, which makes it possible to simulate an elastic collision between balls when studying their acceleration in auto-balancing devices.

Schlüsselwörter

  • Balls
  • centre of suspension
  • elastic collision
  • equations of motion
  • pendulum
Uneingeschränkter Zugang

Specifics of Power Losses in Power Lines Including Parallel Lines

Online veröffentlicht: 23 Jun 2022
Seitenbereich: 155 - 169

Zusammenfassung

Abstract

Reducing power losses is invested in the trend of combating climate warming. It is necessary to know what parameters of power transmission lines affect the losses in them. In short and medium lines with accounted lumped parameters, the role and influence of the line parameters on losses are visible. In the lines with distributed parameters, at least with one series parameter and one parallel parameter, the role played by them, computing losses in ordinary way as difference between power at line sending and receiving end, is hidden. This is pronounced when considering parallel lines. In two parallel lines the losses can be greater than in a single line. This may occur when the current at the end of the lines is less than the boundary value: the value when two parallel lines and a single line have the same losses. The longer the line and the higher the rated voltage, the stronger the effect. In view of this aspect, it is necessary to know the boundary current. This current can be determined in ordinary way by a series of calculations changing the load value. In some cases, boundary current is affected not only by modulus of the current at the end of the line but also by its angle. It is better to calculate the boundary current by a formula, while studying the role of each parameter.

Schlüsselwörter

  • Distributed parameters
  • long lines
  • losses of power lines
  • medium lines
  • parallel power lines
Uneingeschränkter Zugang

Technological Assurance of Ti-6Al-4V Parts Produced by Additive Manufacturing Using Selective Metal Laser Sintering

Online veröffentlicht: 23 Jun 2022
Seitenbereich: 170 - 179

Zusammenfassung

Abstract

The research relates to a technological assurance of Ti6-Al-4V parts produced by additive manufacturing (AM) by means of a metal laser sintering, especially by a fibre laser 3D printer. The influence of technological parameters such as layer thickness, hatch spacing, laser travel speed and laser power have been analysed as well as the influence of thermal treatment as a post processing method has been studied. Technological parameters in combination with a thermal treatment present a challenge in order to manufacture satisfactory products in terms of mechanical properties. The research guides through different phases of experiments to distinguish the best technological parameters. The following research may be used for further investigation of technological assurance for additive manufacturable parts as well as forms the springboard for further research in development of new titanium composites using additive manufacturing methods.

Schlüsselwörter

  • 3D printing
  • additive manufacturing
  • grade 5
  • tensile strength
  • titanium
  • Ti-6Al-4V

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