tedi kurniawan - Academia.edu (original) (raw)

Papers by tedi kurniawan

Publikationsserver der RWTH Aachen University, 2011

Indonesian Journal of Community and Special Needs Education, 2021

The purpose of this paper is to explain the standard for stairs for people with special needs. Th... more The purpose of this paper is to explain the standard for stairs for people with special needs. This study was based on a literature review from various sources, particularly sources in Indonesia. Detailed examples on how to design stairs were presented. This study is hopefully used as a reference and a guide for architectural and environmental construction, particularly in hospitals, schools, and public facilities for people with special needs (i.e. wheelchairs, crutches, and canes for the blind).

In oil and gas industrial environments, carbon dioxide (CO2) and hydrogen sulfide (H2S) contained... more In oil and gas industrial environments, carbon dioxide (CO2) and hydrogen sulfide (H2S) contained in aqueous system are the most common corrosive factors which deteriorate infrastructure made of carbon steel. One of the key factors to accelerate corrosion rate is strain conditions of the steel. Higher strain is suspected to contribute on more hydrogen penetration. This research tested simultaneously the effects pre-strain of carbon steel under saturated CO2 and CO2/H2S environment. The steels were tested in between 5 to 35 percents of initial pre-strain. It showed that the existence of H2S decrease the ultimate tensile strength of the steel. While, the initial pre-strains condition increases the maximum tensile stress. In addition, CO2 and H2S contribute on decreasing toughness.

The purpose of this paper is to evaluate the economic and industrial scale of the production of N... more The purpose of this paper is to evaluate the economic and industrial scale of the production of NiFe2O4 for vehicle batteries using the hydrothermal synthesis method. The method used is to calculate gross profit margin (GPM), payback period (PBP), cumulative net present value (CNPV), total investment cost (TIC), and profitability index (PI). NiFe2O4 nanoparticles were synthesized with the main raw materials being NiCl2•6H2O, FeCl3•6H2O, and NaOH (1:2:8). Calculation results from GPM and CNPV/TIC from the NiFe2O4 industry using the hydrothermal synthesis method show the payback period (PBP) in the third year. So that in the third year onwards it can be predicted that the industry will experience profits. It is expected that NiFe2O4 can be applied on an industrial scale for Li-ion battery anodes.

The formation of protective Cr2O3 layer was usually retarded in the high temperature steam oxidat... more The formation of protective Cr2O3 layer was usually retarded in the high temperature steam oxidation of boiler tube materials. This condition makes the oxidation rate higher than that in dry condition. Therefore in this work, chromizing process is introduced to diffuse chromium on the surface of boiler steel so that it can act as a reservoir for the formation of Cr2O3 layer. The chromizing process was conducted on T91 steel by exposing it into alumina crucible. The crucible was exposed at different temperature (600°C-1050°C) under argon environment in the crucible that contains the chromizing mixture powder of masteralloy Cr, activator NH4Cl and filler Al2O3. It was found that Cr diffusion was happened at higher temperature and it formed Cr carbide on the surface. It also clarified that this chromizing process can prevent the retardation of Cr2O3 layer.

Although clustering has been studied for several decades, the fundamental problem of a valid eval... more Although clustering has been studied for several decades, the fundamental problem of a valid evaluation has not yet been solved. The sound evaluation of clustering results in particular on real data is inherently difficult. In the literature, new clustering algorithms and their results are often externally evaluated with respect to an existing class labeling. These class-labels, however, may not be adequate for the structure of the data or the evaluated cluster model. Here, we survey the literature of different related research areas that have observed this problem. We discuss common “defects” that clustering algorithms exhibit w.r.t. this evaluation, and show them on several real world data sets of different domains along with a discussion why the detected clusters do not indicate a bad performance of the algorithm but are valid and useful results. An useful alternative evaluation method requires more extensive data labeling than the commonly used class labels or it needs a combina...

IOP Conference Series: Materials Science and Engineering, 2017

IOP Conference Series: Materials Science and Engineering, 2019

Indonesian Journal of Chemistry, 2016

The purpose of this study was to investigate influences of temperature on the conversion of ammon... more The purpose of this study was to investigate influences of temperature on the conversion of ammonium tungstate pentahydrate (ATP) powder to tungsten trioxide (WO3) particles with controllable sizes, crystallinities, and physicochemical properties. In this study, we used a simple thermal decomposition method. In the experimental procedure, we explored the effect of temperature on the physicochemical properties of ATP by testing various heating temperatures (from 100 to 900 °C). The heated ATP samples were then characterized by a physical observation (i.e. color) and various analysis methods (i.e. a thermal gravimetric and differential thermal analysis, infrared spectroscopy, an X-ray diffraction, and a scanning electron microscope). Experimental results showed that increases in temperature had an impact to the decreases in particle size, the change in material crystallinity, and the change in physical properties (e.g. change of color from white, orange, to yellowish green). The relat...

Indonesian Journal of Science and Technology, 2016

High temperature oxidation behavior of T91 ferritic/martensitic steel was examined over the tempe... more High temperature oxidation behavior of T91 ferritic/martensitic steel was examined over the temperature range of 500 to 700°C in dry and humid environments. The weight gain result revealed that oxidation occurs at all range of temperatures and its rate is accelerated by increasing the temperature. The weight gain of the oxidized steel at 700°C in steam condition was six times bigger than the dry oxidation.. SEM/EDX of the cross-sectional image showed that under dry condition, a protective and steady growth of the chromium oxide (Cr2O3) layer was formed on the steel with the thickness of 2.39±0.34 µm. Meanwhile for the humid environment, it is found that the iron oxide layer, which consists of the hematite (Fe2O3) and magnetite (Fe3O4) was formed as the outer scale, and spinnel as inner scale. This result indicated that the oxidation behavior of T91 steel was affected by its oxidation environment. The existence of water vapor in steam condition may prevent the formation of chromium ...

2015 IEEE International Symposium on Multimedia (ISM), 2015

Stream data mining has gained a lot of attention over the last years due to an abundance of strea... more Stream data mining has gained a lot of attention over the last years due to an abundance of streaming data in professional as well as personal applications. Solutions have been proposed for many mining tasks such as clustering, classication, frequent item set mining and aggregation. Stream mining is especially challenging due to the large (usually endless) amount of data and the time constraints posed by the stream’s arrival rate. We recently presented an indexbased solution for anytime stream classication that handles both large amounts of data and arbitrary arrival times. In this paper we present our ongoing work, wherein we investigate bulk loading strategies to improve the classication accuracy w.r.t. anytime constraints. We show promising results and discuss future challenges related to index-based classication on data streams. Furthermore we discuss extensions of our technique to other data mining tasks.

Journal of Digital Information Management

Collecting data from sensor nodes is the ultimate goal of Wireless Sensor Networks. This is perfo... more Collecting data from sensor nodes is the ultimate goal of Wireless Sensor Networks. This is performed by transmitting the sensed measurements to some data collecting station. In sensor nodes, radio communication is the dominating consumer of the energy resources which are usually limited. Summarizing the sensed data internally on sensor nodes and sending only the summaries will considerably save energy. Clustering is an established data mining technique for grouping objects based on similarity. For sensor networks, k-center clustering aims at grouping sensor measurements in groups, each contains similar measurements. In this paper we propose a novel resource-aware-center clustering algorithm called: SenClu. Our algorithm immediately detects new trends in the drifting sensor data stream and follows them. SenClu powerfully uses a lightweighted decaying technique that gives lower influence to old data. As sensor data are usually noisy, our algorithm is also outlier-aware. In thorough experiments on drifting synthetic and real world data sets, we show that SenClu outperforms two state-of-the-art algorithms by producing higher clustering quality and following trends in the stream, while consuming nearly the same amount of energy.

2014 10th International Conference on Mobile Ad-hoc and Sensor Networks, 2014

A GPS sensor is utilized to determine the position of objects on earth and it is enormously benef... more A GPS sensor is utilized to determine the position of objects on earth and it is enormously beneficial to society. Despite the advances in GPS technologies, GPS measurement is still susceptible to errors, causing it to only highlight the coarse position of a place or an object. Map matching is the process of matching erroneous GPS sensor readings from a device to a road network. The prime objective of map matching is to rectify the positioning errors associated with GPS measurements. In this paper, we propose a novel map matching technique that utilizes Hidden Markov Model (HMM), tangent distance and some geometric properties of road segments. Specifically, to determine the transition probability of the HMM, we portray a road as a finite interchanging combination of straight lines, transition curves and circular curves, and craft an effective road geometry technique to differentiate circular circle from transition circle using the deflection angle. Besides, we utilize a set of points on each road segment and the tangent distance to compute the emission probability. Subsequently, we employ the Viterbi algorithm to find the most likely road segment to which a sequence of GPS readings correspond to. We conduct numerous experiments at different sampling rates using the Microsoft Seattle real dataset. Our experiments demonstrate that our technique yields a higher map matching accuracy than that of a state-of-the-art work.