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Talib Hussain
"A
vacuum drying system is being designed and developed at National Institute of
Vacuum Science & Technology (NINVAST) to dry various materials under vacuum
conditions. Its performance and capabilities are tested by carrying out
different experiments on green (freshly cut) wood samples of Poplar and
Eucalyptus with dimensions of 990.6 mm x 76.2 mm x 25.4 mm and 469.9 mm x 50.8
mm x 25.4 mm, respectively. These samples were dried from green moisture
content (MC) 78% to 10% by this system at ultimate vacuum of about 1.6 x 103
pascal and at a temperature ranging from 35oC to 55oC for
about 20 hrs. Drying quality tests included: prong test, warp measurement,
surface checking and moisture content measurement, which were all performed.
The resulting wood samples showed no dislocation and no excessive stress
buildup. If compared to ordinary drying process, the vacuum drying is rapid and
the drying rate increases with rise in temperature. The designed system is
beneficial for commercial use."
2016
J-Pdf
Artikel Jurnal  Universitas Indonesia Library
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Talib Hussain
"A vacuum drying system is being designed and developed at National Institute of Vacuum Science & Technology (NINVAST) to dry various materials under vacuum conditions. Its performance and capabilities are tested by carrying out different experiments on green (freshly cut) wood samples of Poplar and Eucalyptus with dimensions of 990.6 mm x 76.2 mm x 25.4 mm and 469.9 mm x 50.8 mm x 25.4 mm, respectively. These samples were dried from green moisture content (MC) 78% to 10% by this system at ultimate vacuum of about 1.6 x 103 pascal and at a temperature ranging from 35oC to 55oC for about 20 hrs. Drying quality tests included: prong test, warp measurement, surface checking and moisture content measurement, which were all performed. The resulting wood samples showed no dislocation and no excessive stress buildup. If compared to ordinary drying process, the vacuum drying is rapid and the drying rate increases with rise in temperature. The designed system is beneficial for commercial use."
Depok: Faculty of Engineering, Universitas Indonesia, 2016
UI-IJTECH 7:5 (2016)
Artikel Jurnal  Universitas Indonesia Library
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Parulian, Junifer Hotma
"Pengeringan beku diakui sebagai metode pengeringan terbaik tetapi sangat intensif energi yang disebabkan dua hal yaitu proses pembekuan pada tekanan yang berbeda dengan pengeringan dan perambatan panas yang lambat selama sublimasi. Proses pembekuan dalam hal ini dihasilkan dari perubahan tekanan dalam suatu tabung vakum yang mengacu pada diagram fasa air dimana seiring dengan penurunan tekanan maka akan terjadi penurunan temperatur dalam suatu ruang sehingga jika suatu produk yang dijadikan sebagai eksperimen diletakkan didalamnya maka akan
terjadi proses pembekukan.
Pada penelitian ini akan dilakukan variasi temperatur coldtrap untuk melihat kemampuan evaporator menangkap uap hasil sublimasi selama proses perubahan fase material, juga analisa potensi energi, dan exergy destruction pada sistem refrijerasi sehingga dapat dilakukan penghematan energi pada pengering beku vakum.

Freeze-drying method of drying is recognized as the best but it is very energy intensive due to two things namely the freezing process at different pressures by drying and heat propagation is slow during the sublimation. The freezing process in this case resulting from changes in pressure within a vacuum tube which refers to the phase diagram of water which along with the decrease of pressure there will be a decrease in temperature in a room so that if a product is used as the experiment is placed in it there will be a process of freeze.
In this study the temperature variation will be conducted to identify the capacity evaporator coldtrap capture vapors during the sublimation process of phase change material, as well as analysis of the potential energy, and exergy destruction in the system so it can be done refrijerasi energy savings in a vacuum freeze dryer.
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Depok: Fakultas Teknik Universitas Indonesia, 2012
S67174
UI - Skripsi Membership  Universitas Indonesia Library
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Tresna Priyana Soemardi
"This study aimed to determine the effect of using acrylonitrile butadiene styrene in place of conventional wax material on treatment pattern removal in the investment casting process. There are three controllable process variables that can affect treatment pattern removal, which include temperature increase, holding time and the number of layers of ceramic shell that have been considered for comparison. Comparison among the effects of temperature increase, holding time and numbers of ceramic shell layers on the ceramic shell was analyzed using ANOVA. It was found that temperature increase (Tx), holding time (t) and number of layers of ceramic shell (N) contribute significantly to the length of the crack (l) on the ceramic shell. The crack in the ceramic shell?s surface was analyzed using scanning electron microscope photos. Less layers number cause the increase of crack length. The combination between temperature upraise and longer holding time cause cracking delay. The experimental is conducted by using 3 (three) variants for each of layers number, temperature and holding time. The layers number is ranging between 7-9 layers. Temperature increase from room temperature until 1300oC. The layers number variant is ranging between 180-300 seconds. It was concluded that a longer holding time will result in a more intact ceramic shell, as longer holding times yield short crack lengths."
2016
AJ-Pdf
Artikel Jurnal  Universitas Indonesia Library
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Dede Sujadi
"Computer simulation program has been developed on the basis of Liapunov approach for the study of MRAC technique applied to pressure control for a vacuum system. Both proportional and integral feedback as well as disturbance feedforward is considered in the closed-loop system. The simulation result obtained with a personal computer demonstrates that this MRAC technique is feasible and provides effective and satisfactory control despite its poor initial control policies and wide range of choice for the adaptive gains. For a series of step disturbance, MRAC resulted in continually improved control with very good agreement obtained between process and reference model responses after the second disturbance."
Depok: Fakultas Teknik Universitas Indonesia, 1989
T-6846
UI - Tesis Membership  Universitas Indonesia Library
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Muhammad Taufiq Suryantoro
"In 2016, the mandatory use of biodiesel as a substitute fuel by up to 20%,
as introduced by the Indonesian Ministry of Energy and Mineral Resources,
forced vehicle manufacturers to invent suitable engines that would accept
biodiesel. The use of biodiesel in such a large proportion is highly risky,
particularly due to the formation of deposits in the combustion chamber
engines. The previous method of fuel droplets are placed on a hot plate
approach produces deposits are slightly different from those generated by a
real engine, therefore to obtain realistic deposits it is necessary to modify
this method so temperatures as hot as those in a real engine. In this study,
the potential deposit formation of biodiesel fuel was examined by conducting
the deposition process and the evaporation of fuel on a stainless-steel plate
(SS), which was placed in a closed space. Deposit characterization was carried out
on a hot plate using Scanning Electron Microscopy (SEM). The test results showed
differences in the structures of the deposits produced by biodiesel and diesel
fuel; fine structures were seen in the former, while those of the latter were
rougher and more porous. Deposit results that are similar to what is seen in a
real engine will be very helpful for knowing the patterns, structures, and mechanism
of the formation of deposits in such an environment."
2016
J-Pdf
Artikel Jurnal  Universitas Indonesia Library
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Azizollah Khormali
"As a result of
waterflooding, inorganic salt precipitation occurs in the different parts of an
oil production system, thereby leading to damage of production equipment.
Different parameters affect the kinetics of salt precipitation. Scale
inhibitors are widely used to prevent inorganic salt formation. In this study,
the effect of reservoir pressure, temperature, and mixing ratio of injection to
formation water on calcium sulfate and barium sulfate precipitation was
investigated. For this purpose, two different formation waters and one
injection water were used. In addition, the effect of temperature and mixing
ratio on inhibition performance was studied. Four different existing industrial
scale inhibitors and one new scale inhibitor were used. The performance of the
scale inhibitors was determined under static and dynamic conditions. Results of
the study showed that calcium sulfate precipitation increased with an increase
in temperature and a decrease in pressure. Barium sulfate precipitation was
found to increase with a decrease in the temperature. The effect of pressure on
barium sulfate formation was negligible. The developed scale inhibitor showed
the highest performance for the prevention of calcium sulfate and barium
sulfate formation. A change in temperature from 60°C to 120°C reduced the
inhibitor performance by 3%. In the cases of calcium sulfate and barium
sulfate, the minimum performance of the scale inhibitor was observed when the
mixing ratios of injection to formation waters were 60:40 and 50:50,
respectively."
2016
J-Pdf
Artikel Jurnal  Universitas Indonesia Library
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Alvin Prayuda Juniarta Dwiyantoro
"The routine daily
activities that tend to be sedentary and repetitive may cause severe health
problems. This issue has encouraged researchers to design a system to detect
and record people activities in real time and thus encourage them to do more
physical exercise. By utilizing sensors embedded in a smartphone, many research
studies have been conducted to try to recognize user activity. The most common
sensors used for this purpose are accelerometers and gyroscopes; however, we
found out that a gravity sensor has significant potential to be utilized as
well. In this paper, we propose a novel method to recognize activities using
the combination of an accelerometer and gravity sensor. We design a simple
hierarchical system with the purpose of developing a more energy efficient
application to be implemented in smartphones. We achieved an average of 95% for
the activity recognition accuracy, and we also succeed at proving that our work
is more energy efficient compared to other works."
2016
J-Pdf
Artikel Jurnal  Universitas Indonesia Library
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Suryadi
"The present
study investigated the mechanical properties and microstructure of ultrafine
grained (UFG) brass processed by four passes of equal channel angular pressing
(ECAP) and annealed at elevated temperatures. The mechanical properties of all
samples were assessed using tensile and micro-hardness tests. Microstructure
analysis was performed using optical microscopy (OM) and scanning electron
microscopy (SEM). Ultimate tensile strengths (UTS) and yield strengths (YS) of
878 and 804 MPa, respectively, ductility of 15%, and hardness of 248 HV were
obtained for samples processed by four passes of ECAP with equivalent true
strain of 4.20. Annealing at 300°C caused UTS and YS to decrease significantly,
to 510 and 408 MPa, respectively, ductility to increase to 28%, and hardness to
decrease to 165 HV. Fractography analysis of un-annealed samples after four
ECAP passes showed small brittle fractures with shallow dimpling. Ductile
failures were found on annealed samples. After four ECAP passes, the
microstructure of un-annealed samples was UFG and dominated by lamellar grain
with shear band. In contrast, after annealing, the microstructure changed due
to recrystallization, showing nucleation and grain growth."
2017
J-Pdf
Artikel Jurnal  Universitas Indonesia Library
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Isti Surjandari Prajitno
"Site Specific Management (SSM), which also variously referred to as Variable Rate Technology (VRT), is an emerging technology that enables producers to make more precise input application decisions based on soil and field characteristics. This study analyzes factors influencing the adoption of VRT for fertilizer application for cash grain production in Ohio. Results show that producer and field characteristics might influence the adoption decision on various SSM components differently. It also provides insight as to the sequence of adoption of SSM component technologies and how this sequence might differ for producers of differing characteristics."
Depok: Lembaga Penelitian Universitas Indonesia, 2003
AJ-Pdf
Artikel Jurnal  Universitas Indonesia Library
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