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Semesta Teknika
Published by Universitas Muhammadiyah Yogyakarta
ISSN : 1411061X     EISSN : 25025481     DOI : https://doi.org/10.18196/st
Core Subject : Engineering,
Engineering
SEMESTA TEKNIKA is a reputable refereed journal devoted to the publication and dissemination of basic and applied research in engineering. SEMESTA TEKNIKA is a forum for publishing high quality papers and references in engineering science and technology. The Journal is published by the Faculty of Engineering, Universitas Muhammadiyah Yogyakarta, INDONESIA. Copyright is by the publisher and the authors. The Journal is issued in electronic form and also issued in printed form as annual volume for the contributors only. The journal contains original research papers, review articles, short notes and letters to the editors. The topics of interest include modeling, experimental, analytical and numerical investigations on the mechanical, physical, chemical and mineralogical properties of material, developing the prototype/instrument, technology and construction process. Topic of management in industry and civil construction is also considered. SEMESTA TEKNIKA receives manuscripts from the contributor written in the Indonesian and English. Manuscripts submitted to the journal for publication must not have been previously published or is under consideration simultaneously by any other publication. Manuscripts submitted to SEMESTA TEKNIKA will be reviewed Peer Reviewers local and foreign.
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Articles 715 Documents
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PERKUATAN STRUKTUR JEMBATAN KERETA API RANGKA BAJA TIPE WARREN BENTANG 42 METER soebandono, Bagus; Nugroho, Bintang Noorohmad Wahyu; Anam, Ariq Naufal; Ismayana, Raka Putra; Maulana, Taufiq Ilham
Semesta Teknika Vol 22, No 2 (2019): NOVEMBER 2019
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Abstract

Jembatan kereta api merupakan salah satu prasarana transportasi penting dalam memenuhi kebutuhan manusia. Seiring dengan bertambahnya usia suatu struktur, maka jembatan kereta api juga akan mengalami penurunan kapasitas yang disebabkan oleh faktor internal maupun faktor eksternal. Melihat dari kegunaan jembatan kereta api yang sangat penting, maka dibutuhkan struktur yang kuat serta mampu menjamin keamanan dan keselamatan. Perkuatan merupakan salah satu usaha untuk mengembalikan kapasitas muat suatu struktur sehingga mampu menahan beban yang terjadi. Dalam penelitian ini jembatan kereta api rangka baja tipe warren mengalami penurunan mutu baja sebesar 30%. Analisis dan pemodelan struktur rangka baja menggunakan software SAP2000 V.20 yang kemudian dilakukan perkuatan dengan mengganti elemen-elemen lemah pada struktur rangka baja. Hasil penelitian menunjukan bahwa, nilai mode shapes maksimum setelah dilakukan perkuatan pada arah perpindahan sumbu global X ( UX ) memiliki nilai yang lebih besar 0,072% dari sebelum dilakukan perkuatan yaitu dari 0,825365 menjadi 0,825962. Nilai periode (T) juga mengalami peningkatan sebesar 1,603% dari 0,370023 detik menjadi 0,375957 detik. Lendutan pada tengah bentang jembatan sumbu lokal horizontal searah bidang XY ( U3 ) mengalami penurunan sebesar 32,85% dari 36,437377 mm menjadi 24,467447 mm. Pada evaluasi tegangan, terdapat 25 batang yang mengalami field capacity yang kemudian dilakukan perkuatan dengan mengganti 17 batang dengan memperbesar dimensi profil sehingga seluruh batang tidak mengalami field capacity. Nilai tahanan maksimum pada batang yang tidak aman setelah dilakukan perkuatan menjadi lebih kecil dari 25,324 ton menjadi 23,861 ton dengan kapasitas yang meningkat dari 12,612 ton menjadi 34,824 ton.The railway bridge is one of the important transportation infrastructures in meeting human needs. As a structured age, the railway bridge will also experience a decrease in capacity caused by internal and external factors. Seeing from the use of the railway bridges which is very important, it takes a strong structure and can guarantee security and safety. Reinforcement is an effort to restore the load capacity of a structure so that it can withstand the burden that occurs. In this study, the warren type steel frame railroad bridge experienced a 30% decline in steel quality. Analysis and modeling of steel frame structure using SAP2000 V.20 software which is then performed strengthening by replacing the weak elements in the steel frame structure. The results showed that the value of the maximum mode shapes after the reinforcement in the direction of global X-axis displacement (UX) has a greater value of 0.072% than before the reinforcement is from 0.825365 to 0.825962. Period value (T) also increased by 1.603% from 0.370023 seconds to 0.375957 seconds. Deflection in the middle of the horizontal local axis bridge spread in the direction of the XY (U3) plane decreased by 32.85% from 36.437377 mm to 24.467447 mm. In the stress evaluation, there is 25 frames that experience field capacity which is then strengthened by replacing 17 frames by enlarging the profile dimensions so that all the bars do not experience field capacity. The maximum resistance value on the unsafe stem after reinforcement is smaller than 25,324 tons to 23,861 tons with capacity increasing from 12,612 tons to 34,824 tons. 
ANALISIS PENGARUH SLOOF TERHADAP PENURUNAN FONDASI TELAPAK DENGAN SIMULASI NUMERIS Adityawan, Muh. Handy Dwi; Adi, Agus Darmawan; Saputra, Ashar
Semesta Teknika Vol 22, No 2 (2019): NOVEMBER 2019
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Sloof yang menghubungkan dua kolom selama ini diperhitungkan sebagai balok ikat (tie beam) agar kolom tidak bergeser. Sloof diasumsikan menggantung atau tidak bertumpu di atas tanah. Sehingga sloof murni sebagai pengikat antar dua kolom. Namun, kenyataan di lapangan sloof bertumpu di atas tanah atau di atas pasangan batu. Oleh karena itu sloof akan menerima beban vertikal dari bangunan. Desain sloof perlu diubah karena kondisi ini. Analisis dilakukan dengan menggunakan program SAP2000. Tanah dan pasangan batu dimodelkan sebagai spring dengan input parameter modulus reaksi tanah dasar (ks). Hasil analisis menunjukkan bahwa penurunan fondasi telapak pada kondisi sloof bertumpu di atas tanah atau di atas pasangan batu lebih kecil dibandingkan kondisi sloof menggantung. Selisih penurunan rata-rata sekitar 26%. Beda penurunan dan angular distortion antara dua kolom menjadi lebih kecil ketika sloof bertumpu di atas tanah atau di atas pasangan batu dibandingkan kondisi sloof menggantung. Momen lapangan yang bekerja pada sloof menggantung adalah positif sedangkan momen tumpuan adalah negatif. Sebaliknya, momen lapangan yang bekerja pada sloof bertumpu di atas tanah maupun di atas pasangan batu adalah negatif, sedangkan momen tumpuan adalah positif.Sloof connecting two columns has been calculated as a tie beam to keep them from moving apart. It was assumed as the hanging sloof or not rested on the ground. Hence it was purely as a tie between two columns. However, in the field, sloof is rested on the ground or the stone foundation. Therefore the sloof will receive the vertical load of the building. The sloof design need to be changed due to this condition. An analysis was conducted using SAP2000. The ground and the stone foundation were modeled as springs at which the modulus subgrade reaction (ks) was the input parameters. The results showed that the settlement of footing when the sloof resting on the ground or the stone foundation was smaller than the hanging sloof. The difference of the settlement was about 26% on average. Differential settlement and angular distortion between two column footings became smaller when the sloof was rested on the ground or the stone foundation compared to the hanging sloof. The field bending moment that occurred on the hanging sloof was positive, while the restraint moment was negative. In contrary, the field bending moment that occurred on the sloof rested on the ground or the stone foundation was negative, while the restraint moment was positive. 
PENGARUH KOMPOSISI BIODISEL JAGUNG TERHADAP SIFAT-SIFAT CAMPURAN BIODISEL JATROPHA-JAGUNG Wahyudi, Wahyudi; Sasuta, Andre; Nadjib, Muhammad
Semesta Teknika Vol 22, No 2 (2019): NOVEMBER 2019
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Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.222249

Abstract

Biodisel merupakan bahan bakar alternatif untuk mesin disel yang biasanya terbuat dari minyak nabati. Minyak jatropha dan minyak jagung merupakan bahan baku biodisel yang potensial. Namun biodisel dari bahan baku minyak jatropha memiliki kelemahan, diantaranya adalah viskositas yang relatif tinggi dan nilai kalor yang relatif rendah. Salah satu upaya perbaikannya adalah pencampuran dengan minyak jagung. Penelitian ini bertujuan untuk mengetahui pengaruh dari variasi komposisi campuran terhadap karakteristik biodisel. Kedua jenis bahan baku diproses menjadi biodisel melalui reaksi transesterifikasi. Selanjutnya dilakukan pencampuran antara biodisel jatropha dan biodiesel jagung. Campuran dibuat dalam sembilan variasi komposisi. Setiap komposisi campuran diaduk dan dipanaskan pada suhu 90 °C selama 60 menit. Hasil penelitian menunjukkan bahwa campuran biodisel jatropha dan jagung memiliki viskositas yang lebih rendah daripada biodisel jatropha murni. Densitas dan titik nyala campuran biodisel tersebut juga mengalami penurunan. Hasil lainnya adalah nilai kalor biodiesel campuran lebih tinggi daripada nilai kalor biodiesel jatropha murni. Biodiesel is an alternative fuel for diesel engines that are usually made from vegetable oil. Jatropha and corn oil are potential biodiesel feedstocks. However, biodiesel from jatropha oil has disadvantages, including high viscosity and relatively low heating value. An effort to improve its properties is mixing it with corn oil. The purpose of this study was to determine the effect of the composition of the mixture on the biodiesel properties. Both raw materials were processed into biodiesel through transesterification reactions. The next step is mixing jatropha and corn biodiesel. There were nine variations of the biodiesel mixture. Each mixture was stirred and heated at 90 °C for 60 minutes. The results showed that the mixture of jatropha and corn biodiesel had lower viscosity than pure jatropha biodiesel. Density and flash point of the biodiesel mixture also decreased. The heating value of mixed biodiesel is higher than its of pure jatropha biodiesel.
PENGARUH KECEPATAN PUTAR TOOL DAN SUDUT SHOULDER SAMBUNGAN FRICTION STIR SPOT WELDING PADA BAHAN POLYPROPYLENE Nugroho, Aris Widyo; Dwi Saputra, Muhammad Rifai; Budiyantoro, Cahyo
Semesta Teknika Vol 22, No 2 (2019): NOVEMBER 2019
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Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.18196/st.222250

Abstract

Penyambungan bahan thermoplastic polypropilen dengan teknik Friction stir spot welding (FSSW) telah banyak dilakukan. Walaupun kekuatannya sudah mencukupi, masih dihasilkan keyhole dan bekas shoulder yang cukup besar karena penggunaan ukuran soulder dan pin besar. Penelitian ini menginvestigasi sambungan polypropilen dengan teknik FSSW menggunakan shoulder dan pin lebih kecil pada geometri shoulder yang berbeda. Penelitian di awali dengan pemotongan lembaran polypropylene dengan panjang 150mm, lebar 30mm dan tebal 5mm. Sambungan tumpang sesuai dengan standar EN 12814-2 digunakan dalam penyambungan ini. Proses penyambungan dilakukan pada kecepatan putar 985, 1660, 2350 rpm dengan dua jenis tool (shoulder angle 0o dan 5o). Sambungan diamati struktur makro, kekerasan dan kapastas beban tariknya. Hasil penelitian menunjukan bahwa semua sambungan memiliki kegagalan getas. Seiring bertambahnya sudut shoulder dan kecepatan putar tool, ukuran nugget dan welding zone meningkat, sehingga meningkatkan kapasitas beban tari mencapai 2116 N. Geometri tool 2 berpotensi untuk dapat diaplikasikan dalam sambungan FSSW. The joining of thermoplastic polypropylene material using the Friction stir spot welding (FSSW) technique has been developed. Although the strength is sufficient, it still produces a large keyhole and shoulder marks due to the use of a large shoulder and pin size. This research investigates polypropylene joint with the FSSW technique using smaller shoulders and pins on different shoulder geometries. The research began by cutting of polypropylene sheets into 150 mm long and 30 mm wide and 5 mm thick. Specimens according to EN 12814-2 were used in this welding joint. The welding process is carried out at rotational speeds of 985, 1660, 2350 rpm with two types of tools (shoulder angle of 0o and 5o). The welding joint was then observed for macrostructure, hardness, and tensile load-bearing capacity. The results showed that all welding joints had a brittle failure. The increasing of the shoulder angle and the rotational speed increase the nugget size and welding zone thickness resulting in a higher tensile load-bearing capacity which reaches up to 2116 N. The tool with the geometric being used has the potential to be applied in the FSSW joint.
Prediksi Beban Listrik Menggunakan Algoritma Jaringan Syaraf Tiruan Tipe Propagasi-Balik Syahputra, Ramadoni; Syahfitra, Febrian Dhimas; Putra, Karisma Trinanda; Soesanti, Indah
Semesta Teknika Vol 23, No 2 (2020): NOVEMBER 2020
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Artikel ini mengusulkan prediksi beban puncak menggunakan metode jaringan syaraf tiruan tipe propagasi-balik. Prediksi beban puncak transformator tenaga merupakan tugas penting dalam mengantisipasi pertumbuhan beban listrik di masa mendatang. Prediksi yang tepat dan akurat akan memfasilitasi perencanaan kapasitas pembangkit listrik yang memadai pada waktu yang tepat. Metode jaringan syaraf tiruan tipe propagasi-balik memiliki akurasi yang baik dalam tugas-tugas prediksi. Pada penelitian ini dilakukan prediksi beban puncak pada dua buah transformator tenaga dengan studi kasus di Gardu Induk Bumiayu, Brebes, Jawa Tengah, Indonesia. Parameter pelatihan adalah data pertumbuhan penduduk, produk domestik regional bruto (PDRB), dan data beban puncak selama sepuluh tahun terakhir. Hasil penelitian menunjukkan bahwa kedua unit transformator tenaga tersebut masih dapat melayani beban listrik di wilayah pelayanan Gardu Induk Bumiayu selama sepuluh tahun ke depan.   This article proposes a peak load prediction using the backpropagation neural network method. Predicting the peak load of power transformers is an important task in anticipating load growth in the future. Precise and accurate predictions will facilitate the planning of sufficient power generation capacity at the right time. The backpropagation type neural network method has good accuracy in the prediction task. In this study, a case study was carried out by predicting the peak load of power transformers at Bumiayu Substation, Brebes, Central Java, Indonesia. Training parameters consists of population growth data, gross regional domestic product (GRDP), and peak load data for the last ten years. The results showed that the two power transformer units could still serve the electricity load in the Bumiayu substation service area for the next ten years.   
Analisis Indeks Keandalan Pembangkit Listrik Tenaga Hibrid Angin-Surya Menggunakan Metode EENS Syahputra, Ramadoni; Noor, Fahrian; Mujaahid, Faaris
Semesta Teknika Vol 23, No 1 (2020): MEI 2020
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Pengembangan sumber energi terbarukan, terutama pembangkit listrik tenaga angin dan surya sangat penting di Indonesia. Hal ini disebabkan kedua jenis pembangkit tersebut dinilai paling potensial dan realistis untuk mendukung program pengembangan energi terbarukan di Indonesia. Dalam penelitian ini disajikan studi tentang indeks keandalan pembangkit listrik hibrid tenaga angin dan surya. Metode untuk menganalisis indeks keandalan adalah metode EENS (expected energy not supplied). Dalam penelitian ini dilakukan analisis lapangan pada pembangkit listrik yang telah beroperasi di Kabupaten Bantul Provinsi Daerah Istimewa Yogyakarta. Hasil penelitian menunjukkan bahwa nilai EENS masih belum memenuhi standar yaitu 0,002% per tahun. Studi yang dilakukan pada tahun 2019 ini menyimpulkan bahwa pembangkit listrik hibrid berbasis tenaga angin dan surya ini belum dapat diandalkan untuk mendukung ketersediaan energi listrik di wilayah Bantul.    The development of renewable energy sources, especially wind and solar power plants, is very important in Indonesia. This fact is because these two types of power plants are considered the most potential and realistic to support renewable energy development programs in Indonesia. In this research, a study on the reliability index of wind and solar-based power plants is presented. The method for analyzing the reliability index is the EENS (expected energy not supplied) method. This study conducted a field analysis on a power plant that has been operated in Bantul district, Yogyakarta Special Region province. The results of the study show that the EENS value still does not meet the standard, namely 0.002% per year. The study conducted in 2019 concluded that wind and solar-based hybrid power plants could not be relied on to support the availability of electrical energy in the Bantul area.     
Penerapan Technology Acceptance Model (TAM) dalam Pengujian Model Penerimaan Aplikasi MasjidLink Mulyanto, Agus; Sumarsono, Sumarsono; Niyartama, Thaqibul Fikri; Syaka, Annisa Khodista
Semesta Teknika Vol 23, No 1 (2020): MEI 2020
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MasjidLink is an Android-based application to provide news and information relating to mosques in the Yogyakarta Special Region. Behavioral aspects that influence tamir when using MasjidLink are need to measure, so that can define the level of acceptance. The TAM (Technology Acceptance Model) approach was used in this research to analyze factors of takmir acceptance towards MasjidLink. The measurement of acceptance  towards MasjidLink with TAM is expected to showing the actual perspective of tamir so can  helps the further developing of this applications. Testing research instruments through validity and reliability. All research instruments have a value of more than 0.5 so that it can be declared as valid instruments. TAM variable in this study has an alpha cronbatch value of more than 0.7, so that all of these research variables are said to be reliable. Perceived ease of use has a percentage value 72.68% which states that mosque takmir agrees with the ease of use of the MasjidLink application. Perception of usefulness has a percentage 72.11% which states that the mosque takmir agrees with the usefulness of the MasjidLink application. Acceptance of the application has a percentage value 71.31% which states that the mosque takmir agrees with the acceptance of the MasjidLink application. The results of descriptive statistical analysis on TAM have the smallest percentage of variables, there is the percentage of MosqueLink acceptance with the value is 71.31%. This can be used to enhance the development of MasjidLink by focusing on the acceptance of the MasjidLink application. MasjidLink is an Android-based application to provide news and information relating to mosques in the Special Region of Yogyakarta. Currently, MasjidLink is a new mosque information management application that was launched and started to implemented by several takmir mosques in the Special Region of Yogyakarta. Takmir's acceptance of the MasjidLink application is one of the factors that support the continued use of the application. The measurement of the mosque takmir acceptance on the MasjidLink application is done by the TAM (Technology Acceptance Model) method. This study aims to evaluate the application of MasjidLink application with the TAM method so that the perception of takmir and the factors that influence takmir in using the application can be known. The research method used is a quantitative method, which uses a questionnaire as a tool to collect data on 125 users of the MasjidLink application. The results showed acceptance of mosque takmir on MasjidLink application had a positive influence on 3 TAM variables, namely the perception of user convenience 72.68%, perceived usefulness of 72.11%, and technology acceptance 71.31%. This shows that the application developer can focus on improving the acceptance of the MasjidLink application variable because the variable percentage is smaller than other variables.
Database Perlintasan Sebidang di JPL 349 dan JPL 350 Menggunakan Software CarryMap Adly, Emil; Widodo, Wahyu; Rahmawati, Anita; Pangestu, M. Ivan Mareza
Semesta Teknika Vol 23, No 2 (2020): NOVEMBER 2020
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 Perlintasan sebidang merupakan jalur 0pertemuan antaraa jalan raya dan jalur kereta api. Pada umumnya banyak terdapat perlintasan sebidang yang tidak memenuhi kriteria teknis dalam menjamin keselamatan pengguna jalan dan kereta api. Permasalahan tersebut bisa menimbulkan kerawanaan terhadap kecelakaan, panjangnya antrian, serta tundaan-tundaan di sisi penguna infrastruktur jalan. Tujuan dan metode penelitian ini adalah untuk menganalisis dan mengevaluasi kinerja ruas jalan berupa tundaan dan panjang antrian menggunakan software VISSIM, memberikan rekomendasi skenario terhadap perlintasan sebidang eksisting menggunakan metode Analytical Hierarchy Process (AHP) dan membuat database yang bisa diakses menggunakan smartphone menggunakan CarryMap. Lokasi penelitian ini adalah pada  Jalan Timoho JPL 349 KM 163+758 dan Jalano Mojo JPL 350 KM 164+536. Setelah dilakukan analisis didapatkan hasil tundaan dan panjang antrian rata-rata terbesar terjadi pada Jalan Timoho. Pada JPL 350 mendapatkan rekomendasi ditutup setelah ada penanganan dan alternatif skenarionya yaitu melengkapi kelengkapan fasilitas infrastruktur perlintasan sebidang atau pengalihan arus lalu lintas ke Jalan Timoho, sedangkan JPL 349 mendapatkan rekomendasi ditutup setelah ada penanganan dan alternatif skenarionya yaitu melengkapi kelengkapan fasilitas infrastruktur perlintasan sebidang atau penaikan status menjadi perlintasan tidak sebidang. CarryMap berisi input data berupa seluruh database yaitu informasi status jalan, koordinat, foto eksising, fasilitas infrastruktur, volume lalulintas, tundaan, panjang antrian serta rekomendasi.A level crossing is a meeting point between the highway and the railroad line. In general, many level crossings do not meet the technical criteria in ensuring the safety of road and railroad users. These problems can cause vulnerability to accidents, long queues, and delays on the side of road infrastructure users. The objectives and methods of this research are to analyze and evaluate the performance of roads in the form of delays and queues, provide scenario recommendations for existing level crossing using the Analytical Hierarchy Process (AHP) method, and create a database that can be accessed using a smartphone using CarryMap. The location of this research was conducted on Jalan Timoho JPL 349 KM 163 + 758 and Jalan Mojo JPL 350 KM 164 + 536. After doing the analysis, it was found that the biggest average delay and queue length occurred at Jalan Timoho. JPL 350 received a recommendation to close after handling and alternative scenarios, namely completing the completeness of level crossing infrastructure facilities or diverting traffic flow to Jalan Timoho, while JPL 349 received a recommendation to close after handling and alternative scenarios, namely completing the completeness of level crossing infrastructure facilities or upgrading the status be a crossing not level. CarryMap contains input data in the form of the entire database, namely information on road status, coordinates, photo exposure, infrastructure facilities, traffic volume, delays, queue length, and recommendations. 
Optimasi Perancangan Timbunan Sampah Perkotaan Studi Kasus TPA Kabinuang Tolitoli Nasril, Moh; Rifai, Ahmad; Faris, Fikri
Semesta Teknika Vol 23, No 1 (2020): MEI 2020
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Pertambahan populasi penduduk khususnya daerah pemukiman kota meningkatkan jumlah sampah padat perkotaan. Sistem pengolahan timbunan sampah pada tempat pembuangan akhir (TPA) kurang efisien sehingga melebihi kapasitas. Berbagai cara diperlukan untuk memaksimalkan kapasitas tempat pembuangan. Lokasi penelitian ini terletak di TPA Kabinuang, Kabupaten Tolitoli. Dalam penelitian ini dilakukan pengambilan sampel di lapangan secara Test Pit di kedalaman 1-2 m pada 3 titik pengamatan mewakili sampel sampah lama (SL), sampah berumur sedang (SS) dan sampah baru (SB) juga sampel tanah dasar (TD) dan tanah penutup (TP). Sampel kemudian diuji kadar organik, kadar air, spesific gravity dan uji triaxial. Data laboratorium kemudian dianalisis dan dilakukan pemodelan dengan variasi lapisan timbunan sampah khususnya pada sampah baru dengan penambahan lapisan tanah penutup. Digunakan program Rocscience (finite element) dan Slide (limit equilibrium) 2 dimensi untuk mendapatkan nilai angka aman dan displacement lereng timbunan sampah pada TPA Kabinuang. Hasil analisis 2D stabilitas lereng timbunan sampah memiliki optimasi desain dengan peningkatan kapasitas timbunan setinggi maksimal 10 m dari kondisi awal dan kemiringan lereng 450 tanpa menggunakan lapisan tanah penutup menghasilkan displacement 0,31 m dan angka aman kondisi statis 3,03 dan 1,16 kondisi dinamis. Apabila digunakan lapisan tanah penutup, kestabilan lereng timbunan sampah meningkat, ditunjukkan displacement yang terjadi lebih kecil yaitu 0,18 m dan angka aman 2,61 kondisi statis dan 1,11 kondisi dinamis.  The increase in the population, especially urban settlements increases the amount of municipal solid waste. The processing system of waste embankment at the landfill (TPA) is less efficient so that it exceeds capacity. Various ways are needed to maximize landfill capacity. The location of this study is located in the TPA Kabinuang, Tolitoli Regency. In this research, the Test Pit was taken in the field at a depth of 0,5-1 m at 3 observation points representing samples of old waste (SL), medium aged waste (SS) and new waste (SB) as well as subgrade samples (TD) and soil cover (TP). The samples were then tested for organic content, water content, Specific Gravity and Triaxial test. Laboratory data are then analyzed and modeling with variations in layers of landfill, especially in new waste with the addition of overburden. 2-dimensional Rocscience (limit equilibrium) and Slides (equilibrium) programs were used to obtain the safe and displacement value of the landfill slope at the Kabinuang landfill. 2D analysis of slope landfill stability has optimized the design with an increase in embankment capacity as high as a maximum of 10 m from the initial condition and slope of 450 without using soil cover resulting in a displacement of 0,31 m and a safety factor of static conditions 3,03 and 1,16 dynamic conditions. If the soil cover  is used, the slofe stability of the landfill increases, indicating that the displacement is smaller, which is 0,18 m and the safety factor is 2,61 static conditions and 1,11 dynamic conditions.
Prediction of Employee Attendance Factors Using C4.5 Algorithm, Random Tree, Random Forest Fahlapi, Riza; Hermanto, Hermanto; Kuntoro, Antonius Yadi; Effendi, Lasman; Nitra, Ridatu Oca; Nurlela, Siti
Semesta Teknika Vol 23, No 1 (2020): MEI 2020
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Research on the performance of workers based on the determination of standard working hours for absences conducted by workers in a certain period. In disciplinary supervision, workers are expected to be able to provide the best performance in the implementation of work in accordance with predetermined working hours. The measurement of the level of discipline of admission hours for placement workers is carried out every working day, continuously and continuously. Attendance monitoring already uses online attendance by using data downloaded from the online attendance provider as the main data. In addition, data collection is done by filtering employee absentee data and supporting information on the categories that cause mismatches in meeting work schedules. Mobilization of workers according to location and working hours has been regulated in company regulations allowing the placement of workers in accordance with the residence so as not to affect the desired work results the company is still within reasonable limits and can be increased. The assessment of this study as a progression factor inhibiting the company in achieving company targets. From the results of the author's analysis of the prediction of employee delay factors using three algorithms, namely the C.45 algorithm accuracy = 79.37% and AUC value = 0.646, Random Forest Algorithm accuracy = 78.58% and AUC value = 0.807 while for the Random Tree algorithm accuracy = 76.26% and the AUC value = 0.610.

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