scholarly journals Development of Sustainable Production Technology of Free-Form Concrete Panels Using a Multi-Point Press CNC Machine

2021 ◽  
Vol 13 (4) ◽  
pp. 1990
Author(s):  
Sunkuk Kim ◽  
Seunghyun Son ◽  
Donghoon Lee
Keyword(s):  
Production Technology ◽  
Technological Development ◽  
Free Form ◽  
Cnc Machine ◽  
Silicon Plate ◽  
Shape Accuracy ◽  
Concrete Panels ◽  
Short Period ◽  
The Mean ◽  
Concrete Materials

Maintaining shape accuracy in the production of concrete panels of free-form buildings is time-consuming and costly. In addition, disposable molds used for free-form panels are not sustainable. Such problems can be solved by developing a suitable computerized numeric control (CNC) machine that can produce an accurately shaped reusable form for free-form concrete materials in a short period of time. This project develops a production technology of quality free-form concrete panels using a CNC machine and verifies the shape quality through an experiment. We designed a multi-point press CNC machine and verified its quality. The CNC machine implements a smooth free-form shape by changing the shape of the silicon plate by movement of the rods. The silicone plate for the CNC machine generates a slight error due to the elastic cover and mechanical clearance. The mean error rate was within 3%, based on the thickness of the panels, at the 95% confidence level. Verification of these errors will provide meaningful information to a similar type of machine development. In addition, the project results will be helpful in technological development for the production of free-form concrete panels of uniform quality, whose shape accuracy is not influenced by the skills and competence of the workers producing the panels.

scholarly journals Energy and CO2 Reduction of Aluminum Powder Molds for Producing Free-Form Concrete Panels

2020 ◽  
Vol 12 (22) ◽  
pp. 9613
Author(s):  
Donghoon Lee ◽  
Sunkuk Kim
Keyword(s):  
Co2 Emissions ◽  
Aluminum Powder ◽  
Energy Use ◽  
Phase Change Materials ◽  
Co2 Reduction ◽  
Free Form ◽  
Cnc Machine ◽  
Repeated Heating ◽  
Concrete Panels ◽  
Reduction Effect

Free-form design may enhance the architectural value of buildings in terms of aesthetic and symbolic effects. However, it is difficult to reuse the mold of free-form concrete segments, so they are manufactured for single use. Manufacturing these molds is a time-consuming process that requires a lot of manpower. To solve these problems, there have been numerous studies on the use of phase change materials (PCMs) to make the molds. PCM molds represent a new technique of producing free-form panels using a computerized numeric control (CNC) machine that employs low-cost material to produce free-form concrete panels. However, PCM molds require a substantial amount of time and energy during fabrication because repeated heating and cooling cycles are required during panel production, and this process increases the CO2 emissions. Thus, the purposes of this study were to develop composite molds using aluminum powder to improve PCM mold performance and to conduct experiments to quantify the reduction of energy use and CO2 emissions. As a result of cooling experiments, it was found that the aluminum powder mold had an energy reduction effect of 14.3% against the PCM mold that had been produced only with paraffin wax, and CO2 reduction effect of more than 50% against the conventional mold.

scholarly journals AN EXPERIMENTAL STUDY FOR QUALITY ASSURANCE OF FREE-FORM CONCRETE PANELS PRODUCED BY CNC MACHINE

2018 ◽  
Vol 24 (2) ◽  
pp. 145-154 ◽  
Author(s):  
Jeeyoung LIM ◽  
Do Yeong KIM ◽  
Sunkuk KIM
Keyword(s):  
Experimental Study ◽  
Quality Assurance ◽  
Labor Cost ◽  
Free Form ◽  
Shape Error ◽  
Cnc Machine ◽  
Concrete Panels ◽  
Short Time ◽  
Change Material

Various studies have been conducted to construct free-form buildings, but it still takes a lot of labor, cost, and time to assure the accuracy of designed shapes. In particular, molds for the production of free-form concrete panels (FCPs) are putting enormous burdens on productivity and cost. To produce FCPs economically, a computerized numeric control (CNC) machine that produces phase change material (PCM) molds for persistent use was developed in this study. The technology using CNC machine can produce precisely free-form molds and panels in a short time compared to the manual method. However, in order to commercialize this technology, it is necessary to verify the shape error of the FCPs. Therefore, the purpose of this paper is an experimental study for securing FCP quality produced by a CNC machine. The results of this study will be used to mass-produce uniform quality of FCPs without depending on the skill and workmanship of the labo.

the effects of resonance with Jupiter in the system of short-period comets

1974 ◽  
Vol 22 ◽  
pp. 193-203
Author(s):  
L̆ubor Kresák
Keyword(s):  
Structural Effects ◽  
Order Resonance ◽  
Mean Motion ◽  
Short Period ◽  
The Mean ◽  
Compound Effect ◽  
Low Order

AbstractStructural effects of the resonance with the mean motion of Jupiter on the system of short-period comets are discussed. The distribution of mean motions, determined from sets of consecutive perihelion passages of all known periodic comets, reveals a number of gaps associated with low-order resonance; most pronounced are those corresponding to the simplest commensurabilities of 5/2, 2/1, 5/3, 3/2, 1/1 and 1/2. The formation of the gaps is explained by a compound effect of five possible types of behaviour of the comets set into an approximate resonance, ranging from quick passages through the gap to temporary librations avoiding closer approaches to Jupiter. In addition to the comets of almost asteroidal appearance, librating with small amplitudes around the lower resonance ratios (Marsden, 1970b), there is an interesting group of faint diffuse comets librating in characteristic periods of about 200 years, with large amplitudes of about±8% in μ and almost±180° in σ, around the 2/1 resonance gap. This transient type of motion appears to be nearly as frequent as a circulating motion with period of revolution of less than one half that of Jupiter. The temporary members of this group are characteristic not only by their appearance but also by rather peculiar discovery conditions.

scholarly journals The Role of Technology in Greenhouse Agriculture: Towards a Sustainable Intensification in Campo de Dalías (Almería, Spain)

Agronomy ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 101
Author(s):  
Antonio J. Mendoza-Fernández ◽  
Araceli Peña-Fernández ◽  
Luis Molina ◽  
Pedro A. Aguilera
Keyword(s):  
Land Use ◽  
Economic Development ◽  
Water Resources ◽  
Natural Resources ◽  
Temporal Evolution ◽  
Technological Development ◽  
Sustainable Intensification ◽  
Short Period ◽  
Cultivation Techniques

Campo de Dalías, located in southeastern Spain, is the greatest European exponent of greenhouse agriculture. The development of this type of agriculture has led to an exponential economic development of one of the poorest areas of Spain, in a short period of time. Simultaneously, it has brought about a serious alteration of natural resources. This article will study the temporal evolution of changes in land use, and the exploitation of groundwater. Likewise, this study will delve into the technological development in greenhouses (irrigation techniques, new water resources, greenhouse structures or improvement in cultivation techniques) seeking a sustainable intensification of agriculture under plastic. This sustainable intensification also implies the conservation of existing natural areas.

scholarly journals The lunar and solar diurnal variations of water-level in a well at Kew observatory, Richmond

1918 ◽  
Vol 94 (663) ◽  
pp. 476-478
Keyword(s):  
Water Level ◽  
Royal Society ◽  
Correlation Coefficients ◽  
Barometric Pressure ◽  
Diurnal Variations ◽  
Range Of Movement ◽  
Nearest Point ◽  
Similar Relation ◽  
Short Period ◽  
The Mean

In a paper communicated to the Royal Meteorological Society, it was shown that the experimental well at Kew Observatory responded to the lunar fortnightly oscillation of mean level in the River Thames, which is 300 yards from the Observatory at its nearest point. The sensitiveness of the water-level to barometric pressure has also been investigated, and the results have been given in a paper recently read before the Royal Society. The present paper deals with the effects of the short-period tides in the solar and lunar series, S 1 , S 2 , S 3 , S 4 , and M 1 , M 2 , M 3 , M 4 . Two-hourly measurements, both in lunar and solar time, were made on the traces obtained during the first two years, August, 1914-August, 1916, omitting days of very irregular movement. Monthly mean inequalities were then computed. Well marked solar and lunar diurnal variations were found in each month, taking the form of double oscillations with two maxima and two minima during the 24 hours. The range of movement was in each case found to be highly associated with the mean height of the water in the well, the correlation coefficients being 0·89 (lunar) and 0·90 (solar). A similar relation had been previously found to exist in the case of barometric pressure.

Synthesis and Properties of Fe3O4 Ferrofluids with Narrow Particle Size Distribution

2011 ◽  
Vol 694 ◽  
pp. 575-579
Author(s):  
Jian Hui Zhang ◽  
Hai Bo Sun
Keyword(s):  
Magnetic Particles ◽  
Particle Diameter ◽  
Free Form ◽  
Narrow Particle Size Distribution ◽  
Particle Sizes ◽  
Bingham Plastic ◽  
Plastic Fluid ◽  
Form Model ◽  
The Mean ◽  
Inference Theory

Fe3O4 ferrofluids with uniform magnetic particles were prepared via improved chemical coprecipation technique. A narrow distribution of 8.6-10.8 nm particle sizes was obtained from the magnetization curve using the free-form-model based on Bayesian inference theory. The mean particle diameter about 9.8 nm is consistent with the XRD and SEM results. The hydrodynamic properties of ferrofluids were investigated with different applied magnetic field and shear rate. The experimental results show that diluted ferrofluid and concentrated ferrofluid are Newtonian-fluid and Bingham-plastic fluid, respectively.

scholarly journals High Terrestrial Radiation Level in an Active Tin-Mine at Jos South, Nigeria

2020 ◽  
Vol 24 (3) ◽  
pp. 435-442 ◽  
Author(s):  
M. Atipo ◽  
O. Olarinoye ◽  
B. Awojoyogbe ◽  
M. Kolo
Keyword(s):  
Gamma Radiation ◽  
Dose Rate ◽  
Technological Development ◽  
Absorbed Dose ◽  
Ground Level ◽  
Absorbed Dose Rate ◽  
Lifetime Cancer Risk ◽  
Radiation Level ◽  
Background Gamma Radiation ◽  
The Mean

Mineral mining and milling can be a source of national economic and technological development. However, mining of minerals has been confirmed to disturb the natural distribution of radioisotopes in the soil, air and water bodies in the biota. In an attempt to evaluate the radiological burden resulting from tin mining activities at Rayfield-Du area of Jos, the background gamma-radiation level in the mine was measured via a well calibratedhand-held dosimeter placed at 1 m above ground level. The mean absorbed dose rate, annual effective dose rate and excess lifetime cancer risk for the mine was 0.83 μSvh-1; 1.44 mSv-1 and 0.005 respectively. Generally, dose rates were higher in the mine pits and processing areas as compared to administrative areas of the mine. The mean measured dose rate and calculated dose parameters for the mine were all high when compared to the regulatory limit for public exposure. The potential of developing radiation-induced health defects as a result of high radiation absorbed dose rate by the miners and dwellers around the mine is highly probable.  Keywords: Gamma-radiation; mine; absorbed dose rate; radiation exposure.

scholarly journals Guidance Stabilization of Satellites Using the Geomagnetic Field

2012 ◽  
Vol 2012 ◽  
pp. 1-9
Author(s):  
Francisco Miranda
Keyword(s):  
Geomagnetic Field ◽  
Technological Development ◽  
Low Cost ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
Small Satellites ◽  
Attitude Stabilization ◽  
Short Period ◽  
Low Earth Orbit Satellite ◽  
Games Theory

In the last years the small satellites have played an important role in the technological development. The attractive short period of design and low cost of them and the capacity to solve problems that are usually considered as problems to big and expensive spacecrafts lead us to study the control problem of these satellites. Active three-axis magnetic attitude stabilization of a low Earth orbit satellite is considered in this work. The control is created by interaction between the magnetic moment generated by magnetorquers mounted on the satellite body and the geomagnetic field. This problem is quite complex and difficult to solve. To overcome this difficulty guidance control is considered, where we use ε-strategies introduced by Pontryagin in the frame of differential games theory. Qualitative analysis and results of numerical simulation are presented.

scholarly journals The Polar Fields and Time Fluctuations of the General Magnetic Field of the Sun

1971 ◽  
Vol 43 ◽  
pp. 675-695 ◽  
Author(s):  
A. B. Severny
Keyword(s):  
Magnetic Field ◽  
Close Agreement ◽  
Present Knowledge ◽  
Short Time Scale ◽  
The Sun ◽  
Statistical Nature ◽  
General Magnetic Field ◽  
Short Period ◽  
The Mean ◽  
Short Time

In an attempt to summarize the present knowledge on the general magnetic field (gmf) of the Sun we pointed out the fine structure and the statistical nature of the gmf as one of its most important properties. The dipole-like behaviour of the mean polar field strengths is combined sometimes (since 1964) with a bias of the S-polarity flux for both poles. Highly uneven distribution of gmf with latitude and longitude, the disappearance of gmf at the South pole for months, and short period, almost synchronous at both poles, variations in the sign of gmf are pointed out. The fluctuations with time of the mean magnetic field of the Sun seen as a star (as well as mf at different latitudes) shows periodicity connected with the rotation of the Sun and very close agreement with the fluctuations of the interplanetary field (sector structure). The effect of faster rotation of N-polarities as compared with S-polarities as well as the bias of mean solar as well as interplanetary S-polarity fields are also pointed out. The possibility of short time-scale (hours) intrinsic changes in the local pattern of gmf is demonstrated.

scholarly journals Design and Evaluation of Uniform LED Illumination Based on Double Linear Fresnel Lenses

2020 ◽  
Vol 10 (9) ◽  
pp. 3257
Author(s):  
Hoang Vu ◽  
Ngoc Minh Kieu ◽  
Do Thi Gam ◽  
Seoyong Shin ◽  
Tran Quoc Tien ◽  
...  
Keyword(s):  
High Speed ◽  
Field Experiments ◽  
Numerical Control ◽  
Free Form ◽  
Light Sources ◽  
Cnc Machine ◽  
Led Lighting ◽  
Positive Effects ◽  
Fresnel Lenses ◽  
Linear Fresnel Lenses

Redistribution of LED radiation in lighting is necessary in many applications. In this article, we propose a new optical component design for LED lighting to achieve a higher performance. The design consists of a commercial collimator and two linear Fresnel lenses. The LED radiation is collimated by a collimator and redistributed by double linear Fresnel lenses to create a square-shaped, uniform distribution. The linear Fresnel lenses design is based on Snell’s law and the “edge-ray principle”. The optical devices are made from poly methyl methacrylate (PMMA) using a high-speed computer numerical control (CNC) machine. The LED prototypes with complementary optics were measured, and the optical intensity distribution was evaluated. The numerical results showed we obtained a free-form lens that produced an illumination uniformity of 78% with an efficiency of 77%. We used the developed LED light sources for field experiments in agricultural lighting. The figures of these tests showed positive effects with control flowering criteria and advantages of harvested products in comparison with the conventional LED sources. This allows our approach in this paper to be considered as an alternative candidate for highly efficient and energy-saving LED lighting applications.

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