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"An improved formula for th eassessment of the external thermal resistance of three buried single-core, metal-sheathed, touching cables, laid in a flat formation, is proposed. The formula arises from the analysis based on a coupled electric- thermal model, as well as on the stochastic optimization method based on differential evolution. The effect of the new formula on cable rating is illustrated in a numerical example. "

"Untuk mencapai sasaran yang optimal dalam pemanfaatan energi panas matahan, perlu dilakukan pengujian dan anahsa lebih lanjut terhadap efisiensi dan performa yang dihasilkan oleh flat plate solar thermal collector dan juga parabolic solar concentrator Pada tugas akhir 1111 akan dibahas proses pengujian terhadap rangkaian kolektor pelat datar dan konsentrator parabolik pada kondisi pengoperasian di daerah Depok untuk dihhat bagaimana karakteristik yang dihasilkan kedua alat tersebut.Pengujian dilakukan dengan menggunakan fluida air yang dialirkan melewati rangkaian 8 kolektor pelat datar dan dilanjutkan dengan pemanasan di 2 konsentrator parabolik Parameter yang dikur adalah temperatur air serta ambient intensitas radiasi matahan dan laju ahran massa Dan sini dapat dihitung karakteristik efisiensi dan juga performa alat up pada kondisi pengoperasian yang bervanasi.Hasil akhir pengujian menunjukkan bahwa efisiensi maksimum untuk kolektor pelat dan konsentrator parabolik berturut turut adalah 43 4% 52 7% dan 30 4% Selain itu juga diperoleh mlai faktor pemindahan kalor dikah dengan koefisien kerugian kalor (FRUL) adalah 3 38 7 49 W/m2K untuk kolektor pelat datar dan 2 69 W/m2K untuk konsentrator parabolik.

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In order to obtain the objective of optimal use of solar thermal collector it is necessary to do testing and analyzing of efficiency and performance result of flat plate solar thermal collector and parabolic solar concentrator. This final project will discuss the process of testing flat plat collectors and parabolic concentrators through operational condition in Depok then observe the characteristic output of both heater.

Experiments be done using water as fluid which flow through 8 connecting flat plat collectors and 2 parabolic concentrators Parameter to be measured is water and ambient temperatures solar radiation intensity and mass flow rate Further more it can be calculated the efficiency characteristic and performance of heater in variation of operational condition.

Final results shown that maximum efficiency of flat plate collector and parabolic concentrator are 43 4% 52 7% dan 30 4% respectively Else it can be calculated that value of heat removal factor multiply by heat loss coefficient (FRUL) are 3 38 7 49 W/m2K for flat plate collector and 2 69 W/m2K for parabolic concentrator."

"[ABSTRAKMaterial Bake Hardening merupakan material yang memiliki sifat mudah dideformasi sebelum diberi perlakuan panas dan sulit dideformasi setelah diberi perlakuan panas. Material ini merupakan material baru yang digunakan pada industri otomotif untuk digunakan pada kerangka mobil dan badan mobil. Material ini akan disambungkan menggunakan mesin Resistance Spot Welding. Resistance Spot Welding merupakan salah satu jenis pengelasan yang banyak digunakan di industri otomotif. Penelitian ini bertujuan untuk mengetahui pengaruh dari parameter kuat arus dari mesin resistance spot welding pada material bake hardening. Penyambungan material bake hardening ini dilakukan dengan menggunakan mesin resistance spot welding dengan pemberian kuat arus 8kA, 9kA, 10kA, 11kA dan 12kA. Pengujian yang dilakukan antara lain pengujian kekerasan, geser, pengamatan SEM, dan metalografi. Hasil penelitian menunjukkan bahwa kekuatan optimum yaitu 5,68kN dan kekerasan optimum yaitu 237,34 VHN didapat pada sampel yang diberi kuat arus sebesar 11kA. Pemberian kuat arus diatas 11kA akan menyebabkan penurunan pada kekuatan dan kekerasan. Pola penjejakan kekerasan menunjukkan bahwa daerah nugget memiliki kekerasan yang lebih tinggi dibandingkan base metal. Struktur mikro juga menunjukkan bahwa semakin ke daerah nugget, butir semakin membesar dan fasa bainite bertambah banyak.

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ABSTRACT

Bake Hardening material is a material that is easily deformed before being given a heat treatment and become a hard deformed after being heat-treated. This material is a new material used in the automotive industry for car frame and car body. This material will be welded using Resistance Spot Welding machine. Resistance Spot Welding is one type of welding that is widely used in the automotive industry. This study aims to determine the effect of the current welding parameters of resistance spot welding to bake hardening material. The joining of bake hardening material is performed using resistance spot welding machine with current 8kA, 9kA, 10kA, 11kA and 12kA. Tests performed include hardness testing, shear, SEM and metallography. The results showed that the optimum tensile strength is 5,68kN and optimum Vickers hardness is 237.34 VHN samples were obtained at a current of 11kA. Giving current 11kA above will cause a decrease in tensile strength and Vickers hardness. Hardness distribution of Vickers hardness shows that nugget area has a higher hardness than the base metal. Microstructure also shows that the area to the nugget, grain growing and increasing bainite phase.;Bake Hardening material is a material that is easily deformed before being given a heat treatment and become a hard deformed after being heat-treated. This material is a new material used in the automotive industry for car frame and car body. This material will be welded using Resistance Spot Welding machine. Resistance Spot Welding is one type of welding that is widely used in the automotive industry. This study aims to determine the effect of the current welding parameters of resistance spot welding to bake hardening material. The joining of bake hardening material is performed using resistance spot welding machine with current 8kA, 9kA, 10kA, 11kA and 12kA. Tests performed include hardness testing, shear, SEM and metallography. The results showed that the optimum tensile strength is 5,68kN and optimum Vickers hardness is 237.34 VHN samples were obtained at a current of 11kA. Giving current 11kA above will cause a decrease in tensile strength and Vickers hardness. Hardness distribution of Vickers hardness shows that nugget area has a higher hardness than the base metal. Microstructure also shows that the area to the nugget, grain growing and increasing bainite phase., Bake Hardening material is a material that is easily deformed before being given a heat treatment and become a hard deformed after being heat-treated. This material is a new material used in the automotive industry for car frame and car body. This material will be welded using Resistance Spot Welding machine. Resistance Spot Welding is one type of welding that is widely used in the automotive industry. This study aims to determine the effect of the current welding parameters of resistance spot welding to bake hardening material. The joining of bake hardening material is performed using resistance spot welding machine with current 8kA, 9kA, 10kA, 11kA and 12kA. Tests performed include hardness testing, shear, SEM and metallography. The results showed that the optimum tensile strength is 5,68kN and optimum Vickers hardness is 237.34 VHN samples were obtained at a current of 11kA. Giving current 11kA above will cause a decrease in tensile strength and Vickers hardness. Hardness distribution of Vickers hardness shows that nugget area has a higher hardness than the base metal. Microstructure also shows that the area to the nugget, grain growing and increasing bainite phase.]"

"Kebutuhan energi semakin meningkat dengan bertambahanya populasi manusia pada saat ini. Salah satu konsumsi energi terbesar adalah pada bidang industri khususnya pada gedung-gedung. Phase Change Material (PCM) merupaka salah satu solusi terhadap permasalahan kebutuhan energi ini. Beeswax merupakan salah satu PCM dengan kapasitas kalor yang tinggi. Material ini akan diuji dan dianalisis pada penelitian ini. Tujuan dari penelitian ini adalah untuk mengetahui sifat-sifat termal dari komposit beeswax dan nanopartikel CuO. Titik leleh dan kapasitas termal dari nano-PCM akan dianalisis dengan metodologi DSC (Different Scanning Calorymeter). Titik leleh dari nano-PCM menurun sebesar 0.6,0.63,0.66,1.07,1.41oC untuk 0.05,0.1,0.15,0.2,0.25 wt % secara berurutan. Tidak ada reaksi kimia diantara beeswax dan nanopartikel CuO berdasarkan hasil dari tes FTIR. Penambahan nanopartikel CuO akan meningkatkan kemampuan perpindahan kalor dari komposit, akan tetapi menurunkan kapasitas kalor dari komposit tersebut. Berdasarkan hasil yang telah didapatkan, penambahan nanopartikel akan meningkatkan kecepatan penghantaran kalor dibandingkan dengan material dasar.The demand of energy is increased in recent days. Experimental and implementation of phase change material as thermal storage is gained greater attention as solution to energy issue. Beeswax as one of phase change material with high thermal capacity is investigated in this paper. The objective of this paper is to analyze thermal properties and behaviors of beeswax-CuO Nano-PCM. The melting temperature and thermal capacity of nano-PCMs were determined by differential scanning calorimetry test. The melting temperature of nano-PCM decreased by 0.6,0.63,0.66,1.07,1.41oC for 0.05,0.1,0.15,0.2,0.25 wt %,respectively. There was no chemical reaction between CuO and beeswax based on FTIR test. Existing of CuO nanoparticles enhanced thermal conductivity of beeswax. Addition of CuO nanoparticles reduced heat capacity of beeswax. However, the change of latent heat would not cause significant effect towards the performance of beeswax-CuO. Thus, based on result, heat transfer of composite beeswax-CuO could be faster than base phase change material."

"Fokus dari penelitian ini adalah pembentukan jet pada jet sintetik aktuator dengan bentuk cavity kerucut pada medium diam (quiescent) terhadap pengaruh diameter orifice. Pengaruh diameter orifice terhadap pembentukan jet diteliti dengan memvariasikan besar diameter yaitu 3 mm, 5 mm dan 8 mm pada frekuensi optimumnya. Tujuan dari penelitian ini adalah untuk memahami kriteria pembentukan jet yang memiliki peranan penting dalam beberapa aplikasi seperti cooling device pada alat-alat elektronik, penggerak wahana bawah air, kontrol separasi aliran, pengurangan drag, dll. Penelitian ini dilakukan secara eksperimental maupun komputasional (CFD). Hasil yang diperoleh adalah jet sintetik aktuator dengan diameter orifice 3 mm dan 5 mm membentuk jet. Namun untuk aktuator dengan diameter orifice 8 mm, jet tidak terbentuk.

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The focus of this study is the formation of jet in synthetic jets actuator (SJA) with conical shaped cavity in quiescent medium that influenced by its orifice diameter. The effect of orifice diameter on the jet formation are inspected by varying the diameter by 3 mm, 5 mm and 8 mm in its optimum frequency. The aim of this study is to understand the jet formation criteria which is important in several application such as cooling device in electronic device, thrust for underwater vehicle, flow separation control, etc. This study is done by experimental and computational method (CFD). The result of this study is the SJA with orifice diameter 3 mm and 5 mm formed the jet. But, for SJA with orifice diameter 8 mm jet are not formed."

"This book presents a wide-ranging review of the latest research and development directions in thermal systems optimization using population-based metaheuristic methods. It helps readers to identify the best methods for their own systems, providing details of mathematical models and algorithms suitable for implementation.To reduce mathematical complexity, the authors focus on optimization of individual components rather than taking on systems as a whole. They employ numerous case studies: heat exchangers; cooling towers; power generators; refrigeration systems; and others. The importance of these subsystems to real-world situations from internal combustion to air-conditioning is made clear.The thermal systems under discussion are analysed using various metaheuristic techniques, with comparative results for different systems. The inclusion of detailed MATLAB® codes in the text will assist readers-researchers, practitioners or students-to assess these techniques for different real-world systems."

"This paper shows the operating principle and experimental results of a new continuous-time sigma-Delta modulator architecture."

"This book trains engineers and students in the practical application of machining dynamics, with a particular focus on milling. The book walks readers through the steps required to improve machining productivity through chatter avoidance and reduced surface location error, and covers in detail topics such as modal analysis (including experimental methods) to obtain the tool point frequency response function, descriptions of turning and milling, force modeling, time domain simulation, stability lobe diagram algorithms, surface location error calculation for milling, beam theory, and more. This new edition includes updates throughout the entire text, new exercises and examples, and a new chapter on machining tribology. It is a valuable resource for practicing manufacturing engineers and graduate students interested in learning how to improve machining productivity through consideration of the process dynamics."