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Abstrak :
This volume provides a practical guide to building and using simulation models for international trade theory and policy. Through a sequence of carefully constructed and fully documented programs, the volume illustrates how GAMS can be used to analyze a wide array of problems. Modern computable general equilibrium (CGE) models for trade policy are challenging in their complexity, but can be thought of as constructions of much simpler building blocks. By developing the building blocks in a consistent manner, and then putting them together in more complex and interesting ways, the volume makes CGE accessible to anyone with a background in microeconomics/​trade theory.

Abstrak :
Proses injeksi merupakan proses yang krusial untuk membentuk produk dalam pengembangan produk metal injection molding (MIM). Adanya perubahan bentuk desain produk, feeding system dan mesin yang digunakan dalam proses eksperimental menjadi dasar bagi penulis untuk melakukan studi lebih lanjut pada proses injeksi baik secara simulasi numerik maupun eksperimental dalam rangka melanjutkan penelitian Universitas Indonesia dalam pengembangan braket ortodonti dengan fabrikasi MIM. Proses eksperimental dan simulasi dilakukan dengan pemberian variasi tekanan injeksi (1200, 1500, 1700 KgF/cm2), temperatur leleh (200, 190, 165 °C), dan temperatur cetakan (55 dan 60 °C). Hasil penelitian menunjukkan bahwa tekanan injeksi dan temperatur cetakan yang lebih tinggi akan berdampak terhadap keterisian cetakan secara volume yang lebih banyak dibandingkan tekanan injeksi yang lebih rendah. parameter terbaik untuk eksperimen injeksi berdasarkan nilai persentase ketercapaian massa injeksi berbanding massa desain adalah injeksi dengan temperatur leleh 165°C, temperatur cetakan 60°C, Tekanan 1700 KgF/cm2 dengan nilai ketercapaian massa injeksi sebesar 47.59% dari total yang didesain pada cetakan. selain itu, Proses simulasi berhasil menggambarkan hasil injeksi dengan rasio ketepatan 89.26% pada proses simulasi injeksi dengan menggunakan temperatur leleh 200 °C, temperatur cetakan 60°C, tekanan 1700 KgF/cm2 dan waktu injeksi 5s ......The injection process is a crucial process in product formation in the development of metal injection molding (MIM) products. The changes in product design, feeding systems and machines used in the experimental process became the basis for the authors to conduct further studies on the injection process both numerically and experimentally in order to continue the study at the University of Indonesia in the development of orthodontic brackets with MIM fabrication. The experimental and simulation processes were carried out by varying the injection pressure (1200, 1500, 1700 KgF/cm2), melting temperature (200, 190, 165 °C), and mold temperature (55 and 60 °C). The results showed that a higher injection pressure and mold temperature would have an impact on the filling of the mold in a larger volume than the lower injection pressure. The simulation accuracy ratio describes the largest injection results obtained in the simulation with a melting temperature of 200 °C, a mold temperature of 60 °C, a pressure of 1700 KgF/cm2 and an injection time of 5s with a success percentage of 89.26% while the best parameters for injection experiments are based on the percentage value of injection mass achievement compared The design mass is injection with a melting temperature of 165°C, a mold temperature of 60°C, a pressure of 1700 KgF/cm2 with an injection mass achievement value of 47.59% of the total designed in the mold.

Abstrak :
The directional solidification which is not toward to riser causes the shrinkage defect. This defect can be predicted by investigating the temperature distribution in riser or casting products. The goal of this research is to examine the temperature distribution using Finite Element Software (ANSYS) and then an ad hoc experiment has been performed to verify the result of the simulation, especially the existences cf shrinkage The simulation is carried out by sand casting process using pure aluminum. This research uses enthalpy method to examine the distribution of temperature. The properties of melted metal that being used for the simulation are enthalpy H(T) and thermal conductivity k(T). For experiment, the sand casting process uses pure aluminum and eutectic aluminum. The eutectic aluminum castings is used to support the pure aluminum castings. The result of the simulation hypothesis against shrinkage defect is appropriate with the experiment result.

Abstrak :
The fluid flow pattern in a thermoacoustic resonator is an important characteristic that affects the performance of the thermoacoustic refrigerator. The main factor that affects the flow and subsequently the heat transfer processes between the oscillating fluid and the stack walls is the geometry of the stack unit, especially related to the stack thickness and stack separation. In this paper, a two-dimensional numerical simulation of the inviscid fluid flow around the stack unit in a quarter wavelength resonator is carried out by using the continuity, Navier-Stokes, energy and ideal gas equations. These equations are solved using the perturbation method and the finite difference method. Three cases of different stack plate thickness are investigated: negligible, 0.4 mm and 0.8 mm thicknesses, respectively. The stack separation has also been varied for the 0.4 mm thickness, within and beyond that recommended by previous studies. Results show that vortices and streaming are always present, more significantly with the thicker plates. Concentrated vortices in the thick plate case stay longer than those with the thinner plate. They contribute to the high heat transfer rate as shown by the temperature profiles.

Abstrak :
Gasifikasi merupakan salah satu thermal-treatment yang dapat dilakukan untuk mengolah biomassa menjadi energi. Syngas merupakan produk utama dari proses gasifikasi, tetapi gasifikasi juga menghasilkan tar yang dapat mengganggu kesehatan manusia, lingkungan maupun peralatan berbahan bakar syngas. Untuk mengurangi kandungan tar, dilakukan modifikasi dalam gasifier dengan menambahkan inlet udara tambahan. Pendekatan model numerik yang digunakan di penelitian ini adalah pemodelan representatif partikel. Dalam penelitian ini, terdapat 2 model yang diusulkan untuk mengkarakterisasi gasifier: gasifier dibagi menjadi 2 kuasi-reaktor (model 1), dan inlet udara primer dan sekunder diasumsikan menjadi satu inlet udara (model 2). Variabel bebas yang digunakan adalah kondisi awal region konveksi campur dan equivalence ratio (ER). Dari hasil penelitian ini, fenomena yang dapat ditangkap di model 1 adalah persebaran temperatur, komposisi partikel, perubahan komposisi syngas terhadap ER dan komposisi tar dalam syngas, sedangkan fenomena yang dapat ditangkap di model 2 adalah komposisi syngas dengan standar deviasi 8,51. Penambahan densitas inlet udara yang berubah terhadap temperatur di kondisi awal region konveksi campur cocok digunakan untuk permodelan gasifier. Kandungan CO dan H2 mengalami peningkatan sedangkan kandungan CO2, CH4 dan H2O mengalami penurunan saat ER dinaikkan. Hasil penelitian menunjukkan model 1 perlu dievaluasi lebih lanjut agar dapat menghasilkan komposisi syngas yang lebih akurat. ......Gasification is one of thermal treatments that could convert biomass into energy. Syngas is the main product of gasification, but gasification also produces tar that could harm human health, environment, and syngas-fuelled equipment. To decrease tar content in syngas composition, modification is done to gasifier by adding secondary air inlet. The numerical approach used in this research was representative particle model (RPM). There were 2 proposed models to characterize gasifier: gasifier was divided into 2 quasi-reactors (model 1), and air inlets were assumed as just one air inlet (model 2). The independent variables were initial conditions of mixed convection region, and equivalence ratios (ER). The results showed model 1 could simulate gasification phenomena, as in temperature distribution, particle composition, change in syngas composition to ER and tar content, while model 2 could simulate the phenomenon as in syngas composition with standard deviation of 8.51. The addition of temperature-dependent air inlet density in gas species mass balance was found suitable for modelling gasifier. The research found CO and H2 contents were increasing, while CO2, CH4 and H2O contents were decreasing as the increase of ER. The research concludes model 1 needs to be further evaluated to approach syngas composition more accurately.

Abstrak :
This paper discusses the design and development of a prototype of a knee surgery cutting jig, the jig holder, and the jig injection mold by Rapid Prototyping (RP). The aim of this study is to design a jig and a jig holder that allow surgeons to correctly, precisely, and consistently perform knee replacement surgery. The design concept for the surgery jig and jig holder was selected using the Pugh method with medical-grade 316L stainless steel for material fabrication. A rapid prototype model was built directly from its CAD model in stereo lithography (STL) format by using the Fused Deposition Method (FDM). MasterCAM and Moldflow simulation were performed to generated G-codes and a possibility of jig fabrication using Metal Injection Molding (MIM), respectively. The Moldflow result provided an enhanced interpretation of the injection mold design. A conceptual mold design was again developed by the FDM. The prototype of the cutting jig and its holder underwent a machining process. The prototype was then tested on dummy bones to determine the functional performance and efficiency of the said prototype. Results indicated an increase in cutting accuracy and cutting time compared with computer-assisted total knee surgery without the jig system.

Abstrak :
Listrik daerah pedesaan yang terisolasi merupakan masalah yang sangat krusial untuk menyelesaikan masalah rasio elektrifikasi di Indonesia. Dibandingkan dengan opsi lain, turbin piko hidro cross-flow (CFT) adalah pilihan yang lebih baik untuk menyediakan daya listrik untuk daerah pedesaan yang terisolasi. Studi untuk meningkatkan kinerja CFT dapat secara analitik, numerik, eksperimental, atau kombinasi metode-metode tersebut. Namun, perkembangan teknologi komputer membuat studi simulasi numerik menjadi semakin sering. Temuan studi CFT yang dilakukan sebelum abad ke-21 terkait dengan parameter desain utama CFT seperti tinggi nosel, sudut serang, sudut pelepasan, atau rasio diameter. Kemudian, pengembangan pendekatan computational fluid dynamic (CFD) diprakarsai oleh Patankar pada tahun 1980 yang mengembangkan penyelesaian masalah aliran fluida numerik berbasis staggered grid, metode diskritisasi upwind orde pertama dan metode Semi Implicit Method for Pressure Linked Equation (SIMPLE). Setelah pengembangan pendekatan CFD cukup matang pada awal abad ke-21, pengembangan CFT menjadi lebih halus dengan modifikasi yang kecil namun efektif. Studi ini telah menghasilkan bahwa model turbulensi yang direkomendasikan untuk simulasi CFD CFT 2D adalah k-E. Disarankan juga untuk menggunakan pendekatan unsteady 6-DOF daripada pendekatan lainnya yang telah ditemukan sebelumnya. Simulasi CFD pada kasus dalam studi ini menggunakan model turbulensi k-E dan pendekatan 6-DOF menghasilkan galat relatif rata-rata 2,99 0,40 dari hasil eksperimen. ......Isolated rural area electricity was very crucial issue to resolve electrification ratio problem in Indonesia. Compared to other options pico hydro cross-flow turbine (CFT) is the better option to provides electrical power for isolated rural area. Studies to improve CFT performance can be undertaken analytically, numerically, experimentally, or combination of those methods. However, the development of computer technology makes numerical simulation studies has becoming increasingly frequent. The finding of CFT studies conducted before 21st century were related to the main design parameter of CFT e.g. nozzle height, angle of attack, discharge angle, or diameter ratio. Then, the computational fluid dynamic (CFD) approach development was initiated by Patankar in 1980 who develop staggered grid based numerical fluid flow problem solving, first order upwind discretization method and Semi Implicit Method for Pressure Linked Equation (SIMPLE) method. After CFD approach development has mature enough at the beginning of 21st century, the development of CFT becoming finer with small but effective modification. This study has resulting that the recommended turbulence model for CFT 2D CFD simulation is k-E. It is also recommended to use 6-DOF unsteady approach instead of other prior approach. The CFD simulations and experiment testing using reccomended turbulence model and unsteady approach produced an average relative error of 2.99 0.40.

Abstrak :
ABSTRACT
Skripsi ini membahas model predator-prey dengan faktor migrasi pada populasi prey dan pemanenan pada populasi predator. Dilakukan proses nondimensionaliasi pada sistem dengan tujuan menjadikan persamaan-persamaan lebih sederhana serta seluruh parameter dan peubah yang terlibat adalah dalam bentuk tanpa dimensi. Analisis secara matematis digunakan untuk menemukan titik keseimbangan pada sistem tanpa faktor migrasi dan pada sistem dengan dua patch. Kestabilan lokal untuk titik-titik keseimbangan kepunahan dan koeksistensi dianalisis menggunakan metode pelinieran dengan matriks Jacobian dan nilai eigennya. Beberapa analisis potret fase disertakan untuk memberikan pema- haman yang lebih baik terhadap kestabilan dari solusi keseimbangan. Simulasi numerik diberikan untuk menunjukkan bagaimana dampak pemanenan populasi predator dan migrasi populasi prey terhadap dinamika populasi dari sistem.

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ABSTRACT
This thesis discusses the predator-prey model with migration factors in the prey population and harvesting in the predator population. Nondimensionaliasi process carried out on the system with the aim of making the equations simpler and all parameters and variables involved are in a dimensionless form. Mathematical analysis is used to find the balance point in systems without migration factors and in systems with two patches. Local stability for points of balance of interest and coexistence was analyzed using the linearity method with the Jacobian matrix and its eigenvalue. Several phase portrait analyzes are included to provide a better understanding of the stability of the balance solution. Numerical simulations are given to show how the impact of harvesting predatory populations and population predation on population dynamics of the system.

Abstrak :
Wilayah geothermal Tulehu ditandai oleh kemunculan manifestasi permukaan. Tidak ada manifestasi yang mengindikasikan zona upflow. Survei geosains telah dilakukan dan diikuti oleh pengeboran 4 sumur eksplorasi. Namun, penggambaran zona upflow suhu tinggi yang terkait dengan sumber panas masih sulit. Hal ini karena area survei geosains yang dilakukan belum mencakup keseluruhan sistem geotermal (daerah upflow dan outflow). Dugaan keberadaan sumber panas kemungkinan menuju G. Eriwakang seperti yang ditunjukkan oleh distribusi temperatur dari data sumur. Berdasarkan studi data geosains yang tersedia, diintegrasikan dengan data sumur yang ada, maka dibuat model konseptual yang mencakup kemungkinan keberadaan sumber panas (zona upflow) di sekitar G. Eriwakang dan kemunculan manifestasi permukaan sebagai zona outflow. Untuk menyelidiki kemungkinan lokasi sumber panas sistem geotermal Tulehu, maka simulasi reservoir dilakukan berdasarkan model konseptual yang telah dibuat dengan menggunakan simulator TOUGH2/iTOUGH2. Hasil simulasi setelah mencapai kondisi natural state menunjukkan bahwa sumber panas dimungkinkan berada di bawah G. Eriwakang. Hal ini ditunjukkan dengan kesesuaian kurva temperatur vs kedalaman antara hasil simulasi dengan data sumur. Untuk mengkonfirmasi hasil penelitian ini, maka direkomendasikan untuk dilakukan survei geosains lebih lanjut. ......Tulehu geothermal area is characterised by surface manifestations. Fumarole and other steam-type manifestations are absent. Geoscientific surveys covering thermal manifestations area have been conducted followed by exploration drillings. However, delineation of high temperature up-flow zone associated with heat source is still challenging, even drilling data from 4 wells could not answer the question yet. Possible existence of the heat source is likely toward Mt Eriwakang as indicated by temperature distribution from wells. Based on the geoscientitic data study, integrated with the existing well data, a conceptual model was developed that includes the possibility of the existence of a heat source (upflow zone) around G. Eriwakang and the appearance of surface manifestations as the outflow zones. To investigate the possible location of the heat source of the Tulehu geothermal system, reservoir simulations using TOUGH2/iTOUGH2 simulator were carried out based on the conceptual model that has been made. Simulation results, after achieving natural state conditions, indicate that the heat source is possibly located under Mt. Eriwakang. This is indicated by the suitability of the temperature vs. depth curve between the simulation results and the well data. Furthermore, to confirm the existence of the heat source, further geoscientific surveys are recommended to be carried out in this area.

Abstrak :
Sebagai salah satu produk asuransi yang sedang mengalami perkembangan pesat, perusahaan asuransi perlu melakukan valuasi terhadap anuitas variabel secara tepat. Terlebih lagi, terdapat banyak fitur tambahan (rider) berupa guaranteed benefit yang disediakan untuk sebuah anuitas variabel. Proses valuasi juga perlu dilakukan terhadap rider guna menghindari kerugian di masa mendatang akibat ketidakmampuan perusahaan untuk melunasi guaranteed benefit milik nasabah. Pada penelitian ini, akan difokuskan mengenai valuasi dari rider Guaranteed Minimum Maturity Benefit (GMMB) dari sebuah kontrak anuitas variabel dengan mempertimbangkan opsi surrender. Metode yang akan digunakan untuk proses valuasi ini adalah dengan mengimplementasikan geometric Brownian motion untuk komponen investasi dan optimal stopping time problem untuk komponen guarantee. Bentuk optimal stopping time problem kemudian akan ditransformasi hingga menjadi persamaan diferensial parsial (PDP) non-homogen, sebelum akhirnya dilakukan pendefinisian formula valuasi untuk guaranteed benefit sekaligus early exercise boundary (EEB) dengan bantuan Duhamel’s principle. Terakhir akan dilakukan perbandingan terhadap formula valuasi guarantee dan kontrak anuitas dari hasil penelitian sebelumnya (Bernard et al., 2014) beserta perhitungan numerik menggunakan data riil dan simulasi numerik dengan variasi parameter. ......As one of the insurance products with recent rapid developments, appropriate valuation of variable annuities should be conducted by insurance companies. Moreover, the existence of additional features (riders) in the form of guaranteed benefits attached to variable annuities increases the necessity for accurate valuation towards the riders to avoid future losses due to the company's inability to pay off the customer's guaranteed benefits. This study will focus more on the valuation of the Guaranteed Minimum Maturity Benefit (GMMB) rider from variable annuities by considering surrender options. The valuation process is done by implementing geometric Brownian motion in the investment component and an optimal stopping time problem for the guarantee. The optimal stopping time problem is then transformed into a non-homogeneous partial differential equation (PDE) before the valuation formula for the guaranteed benefit and the early exercise boundary (EEB) are defined with the aid of Duhamel’s principle. Finally, a comparison test will be made on the accuracy of the valuation formula using results of previous studies (Bernard et al., 2014) along with numerical simulations using existing product rates with variations of parameters based on historical risk-free rate and asset volatility.