Metallurgy Commons^™

Crack Formation In Investment Casting Ceramic Shells, W. A. Everhart

Masters Theses

"This thesis is a collection of papers that discuss shell cracking in investment casting during pattern removal. The application of rigid polymeric foam for large investment casting patterns with complex geometries can improve the dimensional tolerances and the surface quality of the casting. However, these pattern materials have a tendency to promote crack formation in investment casting shells during pattern removal by firing.

The first two papers discuss the factors affecting shell cracking and methods to prevent it. Experimental methods were combined with finite element modeling to predict stress in the shell. A 3D nonlinear finite element model was developed …

Ammoniacal Thiosulphate Leaching Of A Copper-Rich Gold Ore, Ahmet Deniz Bas, Elif Ozdemir, Ersin Y. Yazici, Oktay Celep, Haci Deveci

Ahmet Deniz Bas

No abstract provided.

Dependence Of Microstructure Evolution, Texture, And Mechanical Behavior Of A Mg Alloy On Thermo-Mechanical Input During Friction Stir Processing, Zhenzhen Yu

Doctoral Dissertations

In this thesis, the relationship among friction stir processing (FSP) parameters, microstructure evolution, texture development, and mechanical hehavior of AZ31B Mg alloy was investigated.

First of all, in order to reveal the correlation among the deformation conditions, dynamic recrystallization (DRX) mechanisms, and microstructure evolution in the Mg alloy, hot compression tests at a wide range of Zener-Hollomon parameter (Z) values were conducted. Through optical microscopic examination, it was found out that above a critical Z value, twinning influences the DRX process resulting in a more effective grain refinement, which is manifested in a significant change in the slope of the …

Energetics And Kinetics Of Dislocation Initiation In The Stressed Volume At Small Scales, Tianlei Li

Doctoral Dissertations

Instrumented nanoindentation techniques have been widely used in characterizing mechanical behavior of materials in small length scales. For defect-free single crystals under nanoindentation, the onset of elastic-plastic transition is often shown by a sudden displacement burst in the measured load-displacement curve. It is believed to result from the homogeneous dislocation nucleation because the maximum shear stress at the pop-in load approaches the theoretical strength of the material and because statistical measurements agree with a thermally activated process of homogeneous dislocation nucleation. For single crystals with defects, the pop-in is believed to result from the sudden motion of pre-existing dislocations or …

Effect Of Moisture Absorption On The Sinter Quality Of Central Solenoid (Cs) Coil Pack, Zeshaan Sher Mohammed

Masters Theses

Fusion energy has been said to be the solution to all the world’s energy problems. The International Thermonuclear Experimental Reactor (ITER) is the flagship project to demonstrate the feasibility of fusion energy. The Central Solenoid (CS), an important component of the reactor, is needed to induce plasma current, initiate, ramp-up, ramp-down, and sustain plasma in a very controlled manner. In order to achieve this, the CS coil packs must be manufactured under controlled conditions. The CS conductor is an advanced cable-in-conduit Nb3Sn superconductor. The CS cable will be made in long continuous sections but with thousands of meter of cable …

Dye Sensitized Solar Cell With Conventionally Annealed And Post-Hydrothermally Treated Nanocrystalline Semiconductor Oxide Tio2 Derived From Sol-Gel Process, Akhmad Herman Yuwono, Badrul Munir, Alfian Ferdiansyah, Arif Rahman, Wulandari Handini

Makara Journal of Technology

Dye-sensitized solar cell (DSSC) is one of the very promising alternative renewable energy sources to anticipate the declination in the fossil fuel reserves in the next few decades and to make use of the abundance of intensive sunlight energy in tropical countries like Indonesia. In the present study, TiO2 nanoparticles of different nanocrystallinity was synthesized via sol−gel process with various water to inorganic precursor ratio (Rw) of 0.85, 2.00 and 3.50 upon sol preparation, followed with subsequent drying, conventional annealing and post-hydrothermal treatments. The resulting nanoparticles were integrated into the DSSC prototype and sensitized with an organic dye made of …

Remote Sensing And Geographical Information System To Identify Drought Potency, Puguh Dwi Raharjo

Makara Journal of Technology

Remote Sensing and Geographical Information System to Identify Drought Potency. Kebumen regency was drought in year 2008, community clean water shortages and irrigation water following a decline in water resources. The use of remote sensing data and GIS can be used to identify the potential for drought-prone areas. Transformation of Landsat TM satellite imagery to obtain the brightness index, wetness index and vegetation index used to determine surface conditions in relation to drought. Brightness index and wetness index derived from the tasseled cap modifications, while the vegetation index derived from normalized difference vegetation index (NDVI) values. Other parameters such as …

Immobilization Of Saccharomyces Cerevisiae In Rice Hulls For Ethanol Production, Edita Martini, Dian Andriani, Sriramulu Gobikrishnan, Kyeong Eop Kang, Surn-Teh Bark, Changshin Sunwoo, Bambang Prasetya, Don-Hee Park

Makara Journal of Technology

The whole cell immobilization in ethanol fermentation can be done by using natural carriers or through synthetic carriers. All of these methods have the same purpose of retaining high cell concentrations within a certain defined region of space which leads to higher ethanol productivity. Lignocellulosic plant substance represents one of highly potential sources in ethanol production. Some studies have found that cellulosic substances substances can also be used as a natural carrier in cell immobilization by re-circulating pre-culture medium into a reactor. In this experiment, rice hulls without any treatment were used to immobilize Saccharomyces cerevisiae through semi solid state …

An Empirical Model For Build-Up Of Sodium And Calcium Ions In Small Scale Reverse Osmosis, Subriyer Nasir

Makara Journal of Technology

A simple models for predicting build-up of solute on membrane surface were formulated in this paper. The experiments were conducted with secondary effluent, groundwater and simulated feed water in small-scale of RO with capacity of 2000 L/d. Feed water used in the experiments contained varying concentrations of sodium, calcium, combined sodium and calcium. In order to study the effect of sodium and calcium ions on membrane performance, experiments with ground water and secondary effluent wastewater were also performed. Build-up of salts on the membrane surface was calculated by measuring concentrations of sodium and calcium ions in feed water permeate and …

Simulation On The Use Of Losat Data For Rice Field Mapping, Bambang H. Trisasongko, Dyah R. Panuju, Boedi Tjahjono, Baba Barus, Hari Wijayanto, Mahmud A. Raimadoya, Irzaman Irzaman

Makara Journal of Technology

Simulation on the Use of LOSAT Data for Rice Field Mapping. Since the launch of LAPAN-TUBSAT satellite in 2007, Indonesia has been developing mission on earth observation missions for various applications. The next generation mission, called LAPAN-ORARI Satellite (LOSAT), is currently under development and expected to be launched in 2011. In order to facilitate the applications, a thorough assessment of the sensor should be made. This paper presents an examination of simulated LOSAT data for rice monitoring and mapping purposes coupled with QUEST statistical tree. We found that three-band simulated LOSAT data were suitable for the task with reasonably high …

Shaft Torsional Vibration Response Of Vertical Axis Ocean Current Turbine Model Due To Torque Excitation, Adi Wirawan Husodo, I Ketut Aria Pria Utama, I Made Ariana

Makara Journal of Technology

Shaft Torsional Vibration Response of Vertical Axis Ocean Current Turbine Model Due to Torque Excitation. The current research aimed to study the torsional vibration response of Vertical Axis Ocean Current Turbine due to randomly torque excitation pattern, owing to the variety of ocean current velocity. The turbine model is composed of 3 aluminum blades of NACA 0018 connected to steel shaft. Turbine dimensions are 10 cm of chord, 1.8 cm of chamber and 100 cm of span. The variation of ocean current velocity is 0.5 m/s, 1.0 m/s, 1.5 m/s, 2.0 m/s, 2.5 m/s and 3.0 m/s. The Model has …

The Stability Characteristics Of Sandbag Submerged Breakwater, Ferry Fatnanta, Widi Agoes Pratikto, Haryo Dwito Armono, Wahyudi Citrosiswoyo

Makara Journal of Technology

The Stability Characteristics of Sandbag Submerged Breakwater. Breakwater is one of coastal structures to overcome problems of abrasion. Due to difficulties in obtaining rock material at the coastal area. The using of sandbags as a breakwater provides advantages in utilizing local materials. A Sandbag has a smooth surface, so the internal shear forces are relatively small. According to these phenomena, the research for parameters that are expected to affect the stability of the sand bags. These parameters are a slope, shape and formation of sand bags. This experimental research conducted in two dimensional physical model and took place on the …

Static Hand Gesture Recognition Of Indonesian Sign Language System Based On Backpropagation Neural Networks, Farida Asriani, Hesti Susilawati

Makara Journal of Technology

Static Hand Gesture Recognition of Indonesian Sign Language System Based on Backpropagation Neural Networks. The main objective of this research is to perform pattern recognition of static hand gesture in Indonesian sign language. Basically, pattern recognition of static hand gesture in the form of image had three phases include: 1) segmentation of the image that will be recognizable form of the hands and face, 2) feature extraction and 3) pattern classification. In this research, we used images data of 15 classes of words static. Segmentation is performed using HSV with a threshold filter based on skin color. Feature extraction performed …

The Effect Of Enzymatic Hydrolysis On The Properties Of Protein Hydrolysate From Paddy Mushroom, Niken Widya Palupi, Wiwik Siti Windrati, Tamtarini Tamtarini

Makara Journal of Technology

Protein hydrolysate was prepared from Paddy (Volvariella volvaceae) mushroom. Hydrolysis uses commercially protease available Protamex ™ with enzyme concentration of 0.1% (w/w). Hydrolysis was performed at three different temperatures (room temperature, 40 °C, and 50 °C) with different incubation periods (60, 90, and 120 minutes). Enzyme inactivation was done in 90 °C for 3 minutes. Yield and degree of hydrolysis ranged from 94.76% to 99.55% and 19.06% to 24.59%. Protein solubility was about 89–11,8%. The longer time of hydrolysis, the darker the color of protein hydrolysate. Protein hydrolysate which has hydrolysis at 50 °C for 120 minutes has the highest …

Plant Growth Modeling Using L-System Approach And Its Visualization, Atris Suyantohadi, Alfiyan Alfiyan, Mochamad Hariadi, Mauridhi Hery Purnomo

Makara Journal of Technology

The visualization of plant growth modeling using computer simulation has rarely been conducted with Lindenmayer System (L-System) approach. L-System generally has been used as framework for improving and designing realistic modeling on plant growth. It is one kind of tools for representing plant growth based on grammar sintax and mathematic formulation. This research aimed to design modeling and visualizing plant growth structure generated using L-System. The environment on modeling design used three dimension graphic on standart OpenGL format. The visualization on system design has been developed by some of L-System grammar, and the output graphic on three dimension reflected on …

Separation Study Of Titanomagnetite Fe3-Xtixo4 From Natural Sand At Indramayu, West Java, Sunaryo Sunaryo, Iwan Sugihartono

Makara Journal of Technology

Separation Study of Titanomagnetite Fe3-xTixO4 from Natural Sand at Indramayu, West Java. Titanomagnetite FeTiO4 has been obtained from metal sand which is separated from natural sand at Indramayu using magnetic separator with the magnetic field 0,3 Tesla. This method can improve titanomagnetite content from 32% to 63,6%. According to X-ray diffractometer (XRD) and data processing by general structure analyses system (GSAS) with χ2= 1,454 and Wrp = 0,1142 as correction factor of the peak to peak intensities, we conclude that χ2 about 0 and Wrp aproximately 10%. It indicates the datas with the error merely 0,1 can be accepted. Furthermore, …

Concept Design And Testing Of Multi-Nozzle Water Mist Fire Suppression System, Danardono A. Sumarsono, Yulianto S. Nugroho, Mariance Mariance, I Gede Wahyu W. Ariasa

Makara Journal of Technology

In this work a flexible design of multi-nozzle arrangement of water mist fire suppression system was studied. The source of fire was a 65 mm diameter cooking oil fire. An investigation on the impact of nozzle arrangement on the temperature profile of fires was conducted. The occurance of oil splash due to the application of water mist was also studied. The water mist systems developed in the present work can effectively extinguish cooking oil fires and prevented them from re-ignition. The spray angle, discharge pressure, and water flow rate were important factors to determine the effectiveness of water mist in …

Development Of Technology Parameter Towards Shipbuilding Productivity Predictor Using Cubic Spline Approach, Bagiyo Suwasono, Sjarief Widjaja, Achmad Zubaydi, Zaed Yuliadi, I Nyoman Budiantara

Makara Journal of Technology

Development of Technology Parameter Towards Shipbuilding Productivity Predictor Using Cubic Spline Approach. Ability of production processes associated with state-of-the-art technology, which allows the shipbuilding, is customized with modern equipment. It will give impact to level of productivity and competitiveness. This study proposes a nonparametric regression cubic spline approach with 1 knot, 2 knots, and 3 knots. The application programs Tibco Spotfire S+ showed that a cubic spline with 2 knots (4.25 and 4.50) gave the best result with the value of GCV = 56.21556, and R2 = 94.03%.Estimation result of cubic spline with 2 knots for the PT. Batamec shipyard …

Wimax Implementation As Existing Hotspot Network Backhaul In Jakarta, Djamhari Sirat, Muhamad Asvial, Luther B. Marpaung

Makara Journal of Technology

WiMAX Implementation as Existing Hotspot Network Backhaul in Jakarta The development of Broadband Wireless Access (BWA), such as WiMAX, as a global standard for data transmission media has been used by high speed internet access provider. WiMAX application which supported by capabilities of interoperability, flexibility and commercial aspect make the internet services become more efficient, cheaper and easier to the customer. This phenomenon should be responded by ISPs. Based on technical and financial aspect in deciding the implementation of Wireless Network with WiMAX technology as a substitute, this research will observe and analyze the projection of WiMAX technology implementation as …

High Pressure Adsorption Isotherm Of Co2 On Activated Carbon Using Volumetric Method, Awaludin Martin, Bambang Suryawan, Muhammad Idrus Alhamid, Nasruddin Nasruddin

Makara Journal of Technology

High Pressure Adsorption Isotherm of CO2 on Activated Carbon using Volumetric Method. Adsorption system is ones of the most effective methods for CO2 separating with other substances that produced from the burning of fossil fuels. In the design for that application, beside of characteristics of porous material (adsorbent) data, CO2 adsorption data on the adsorbent (kinetic and thermodynamic) are also needed. The aim of this research is resulting isothermal adsorption data at pressures up to 3.5 MPa by indirect methods (volumetric method) at isothermal temperature of 300, 308, 318 and 338 K. Adsorbent that used in this research is activated …