USU-IR Repositori Institusi Universitas Sumatera Utara
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Experimental Study of Copper Addition and Cooling Media Variation Effects on Al-Si Alloy's Mechanical Properties and Microstructure for Gear Application
No full textThis study investigates the effects of copper addition (8%, 10%, 12%) and cooling
media variation (air, SAE 40 oil, water) on the mechanical properties and
microstructure of sand-cast Al-Si alloy for gear transmission applications. A factorial
experimental design was employed with independent variables of Cu composition and
cooling media, while dependent variables included Vickers hardness (ASTM E92),
Charpy impact toughness, density (Archimedes method), and microstructure analysis.
Key findings reveal Copper Influence is Hardness increased linearly with Cu content
(253.3 VHN at 12% Cu) due to Al₂Cu intermetallic phase formation, but accompanied
by reduced impact toughness (from 0.0331 J/mm² to 0.0217 J/mm²). Cooling Media
Effects Water quenching achieved peak hardness (266.3 VHN) but lowest impact
toughness (0.0217 J/mm²), while air cooling yielded more ductile structures with
optimal density (2.78 g/cm³). Microstructural Analysis is Quenching caused
heterogeneous Al₂Cu distribution with localized porosity, whereas air cooling
produced more homogeneous phase distribution. The optimal combination was found
in Al-Si-10%Cu with oil cooling, demonstrating balanced properties (196.3 VHN
hardness and 0.025 J/mm² impact toughness). However, these results remain below
industrial standards for motorcycle gear applications (>250 VHN). The study
suggests75 PagesSkripsi Sarjan
Utilization of Hdpe and Pet Plastic Waste As Aggregate Substitutes On The Mechanical Properties of Paving Blocks
No full textWaste is a serious issue for the environment, health, and the economy. Plastic, in particular, is a major contributor. From 1950 to 2018, global plastic production reached over 8 billion tons, with plastic bottles being one of the main contributors. To address the accumulation of plastic bottle waste, one innovative solution is to utilize it in construction products.This study investigates the effects of HDPE (High-Density Polyethylene) and PET (Polyethylene Terephthalate) plastic waste as aggregate substitutes in paving blocks on mechanical properties, durability, cost, and surface morphology. Compressive strength tests showed that the control paving block (25.38 MPa). The addition of plastic waste reduced performance, with the optimal compressive strength found in 5% HDPE (21.24 MPa) and 5% PET (22.32 MPa), while the lowest was at 15% HDPE (14.62 MPa). The highest water absorption (1.36%) occurred in 5% HDPE, while the lowest was in 15% PET. An increase in plastic content reduced water absorption due to the hydrophobic nature of plastic.In the sodium sulfate resistance test, the weight difference between the control paving block and those with plastic additions was ≤1% after five soaking cycles, with no visible or structural cracks or defects. The impact test showed the best performance at 5% plastic content (withstood up to 10 blows), while the 15% plastic variation only withstood 5 blows. Scanning Electron Microscopy (SEM) results showed that paving blocks with plastic substitution had few voids, but the plastic–aggregate bond was weak due to the smooth surface and differences in chemical properties. Economically, using plastic waste as an aggregate substitute in paving blocks reduced material costs by 1.78% and plastic waste by 7.35 kg/m². Although plastic–aggregate adhesion still needs optimization, test results indicate that plastic waste has the potential to serve as an environmentally friendly alternative material with adequate performance for sustainable paving block applications.156 PagesTesis Magiste
Financial Feasibility Analysis of Oil Palm Farming in Tanah Jawa District Simalungun Regency North Sumatra Province
No full textThis study examines the financial feasibility of oil palm farming using the NPV, IRR, and B/C
Ratio methods, as well as how farmers' strategies to increase the viability of oil palm farming
in Tanah Jawa District, Simalungun Regency, North Sumatra Province. The analysis results
show that oil palm farming in Tanah Jawa District, Simalungun Regency, North Sumatra
Province is feasible because it meets the evaluation criteria with NPV > 0, which amounts to
Rp 7.067.293.269,61, IRR > the interest rate at 34,71%, and Net B/C > 1, which is 14,62.
The strategy implemented by oil palm farmers in Tanah Jawa District, Simalungun Regency,
North Sumatra Province to enhance the viability of their farming is still focused on
increasing production through appropriate fertilization.92 PagesSkripsi Sarjan
Proposed Facility Layout Improvements at PT. Asia Raya Foundry Using Value Stream Mapping and Graphic Methods
No full textPT. Asia Raya Foundry is a manufacturing company engaged in metal casting, particularly in the production of screw press components. However, the production process has not been running efficiently due to issues in the facility layout and production flow, such as backtracking, by-passing, and excessively long distances between workstations. This study aims to design an improved facility layout and production flow that is more efficient, in order to reduce waste and increase productivity. The methods used in this study are Value Stream Mapping (VSM) to identify waste activities in the production flow, and a graph-based method utilizing the from-to chart to design a proposed layout based on the weight and frequency of material transfers between workstations. The analysis results indicate that Non-Value Added (NVA) activities are quite dominant, with a waiting time of 125.45 hours out of a total production time of 212.7 hours. The most significant waste occurred at the moulding and fettling stations, which were resolved through batch size adjustments and rescheduling. The proposed layout successfully reduced the total transfer moment from 49,784.69 m/month to 30,719.62 m/month. In addition, the Line Efficiency Rate (LER) increased significantly from 58.6% to 95.23%, indicating a substantial improvement in efficiency. Therefore, the proposed improvements in this study have successfully optimized the material flow and facility layout at PT. Asia Raya Foundry.150 PagesSkripsi Sarjan
Factors Related to Tinea Pedis Complaints in Car Wash Service Workers in Rantau Selatan Sub-District Rantauprapat City in 2025
No full textTinea pedis also known as athlete's foot, is a common fungal skin infection affecting the feet, estimated to impact 3 percent of the world's population, especially in humid tropical climates like Indonesia. This disease is frequently found in individuals working in wet and damp environments, including car wash workers who are continuously exposed to water and high humidity. These working conditions, coupled with a lack of personal hygiene practices, create an ideal environment for the growth of dermatophyte fungi. Tinea pedis symptoms, which vary from itching to severe pain, can disrupt worker productivity. Given the high percentage of informal workers in Indonesia, including the car wash service sector, as well as initial findings of Tinea pedis complaints among workers in Rantau Selatan Sub-District, this study aims to identify factors related to Tinea pedis complaints in car wash service workers in Rantau Selatan Sub-District Rantauprapat City in 2025. This study is a quantitative analytical research with a cross-sectional approach. The study population was all car wash workers in Rantau Selatan Sub-District, with a total sampling of 31 respondents. The independent variables studied were age, length of service, working hours, and personal hygiene. Tinea pedis complaints were measured through questionnaires and direct interviews with car wash workers. Data analysis used the chi-square test with a 95 percent confidence level (α=0.05). The research results showed no relationship between age and Tinea pedis complaints (p=0.981). Meanwhile, there was a relationship between length of service (p=0.002), working hours (p=0.009), and personal hygiene (p=0.027) with Tinea pedis complaints. The majority of workers experienced itching and stinging complaints in their foot area. Workers should pay close attention to personal hygiene, particularly correct foot care, ensuring their feet remain dry to avoid creating damp conditions that contribute to the risk of Tinea pedis.97 PagesSkripsi Sarjan
Effectiveness of Ethanol Extract Nanocream from Pegagan Leaves (Centella asiatica (L.)Urb.) as an Anti-Aging
No full textBackground: Skin aging was a natural process that could have been accelerated by
exposure to free radicals, UV rays, and oxidative stress. Pegagan leaves (Centella
asiatica (L.) Urb.) were known to contain high levels of antioxidants and active
compounds such as flavonoids and triterpenoids, which had the potential as anti
aging agents. Nano cream was used because it could enhance the penetration of
active ingredients into the skin.
Objective: The study aimed to formulate ethanol extract of pegagan leaves into a
stable nano cream preparation and to analyze the effectiveness of the ethanol extract
nano cream as an anti-aging agent.
Method: This research involved stages of extraction of pegagan leaves using 96%
ethanol solvent, followed by antioxidant activity testing using the DPPH (2,2
diphenyl-1-picrylhydrazyl) method, and formulation of ethanol extract nano cream
preparations with the addition of ethanol extract at concentrations of 0.1% (F1),
0.2% (F2), 0.3% (F3), and without extract (F0). Evaluation of the nano cream
included organoleptic tests, homogeneity, emulsion type, pH, viscosity, particle size
measurement, physical stability at room temperature for 12 weeks, and cycling test.
The anti-aging effectiveness test was carried out over a 4 week treatment period,
measuring parameters such as moisture, pore size, spot appearance, and wrinkles on
the back of the volunteers' hands once a week using a skin analyzer tool.
Results: The antioxidant activity test of the ethanol extract of pegagan leaves
showed very strong activity with an IC50 value of 23.24 µg/mL. The nano cream
preparation had a semi-solid texture, light green colour, homogeneous, with M/A
emulsion type, stable under centrifugation test, spreadability of 5.18–6.82 cm, pH
5.85–6.26, viscosity of 20898.67–41419.00 cP, particle size met the requirement
(<500 nm), stable at room temperature for 12 weeks, and stable in the cycling test.
The nano cream with 0.3% concentration (F3) showed better effectiveness than
concentrations of 0% (F0), 0.1% (F1), and 0.2% (F2). Average percentage
improvements at 0.3% (F3) as follows: moisture 76.39%, pores 73.21%, spots
49.39%, and wrinkles 52.47%.
Conclusion: The ethanol extract of pegagan leaves could be formulated into a nano
cream preparation that met evaluation requirements and demonstrated optimal anti
aging effectiveness at a concentration of 0.3% (F3).137 PagesSkripsi Sarjan
The Growth and Production Responses of Sorghum (Sorghum bicolor (L.) Moench) on Application of Coffee Skin Waste and NPK Fertilizer
No full textThe aim of this study was to determine the influence of coffee bark waste
as a growing medium and the addition of NPK fertilizer on the growth and
production of sorghum plants. The study was conducted on community land in Jalan
Harmonika Baru, Padang Bulan Selayang II, Medan Selayang District, Medan in
June to November 2022. The study used a two-factor Randomized Group K (RAK)
and three iterations, the first factor being Coffee Skin Waste and the second factor
being NPK 16-16-16. The observed variables are plant height, trunk diameter,
weight of fresh shoots, weight of dry shoots, weight of fresh roots, weight of dry
roots, weight of 1000 seeds, weight of sample seeds, weight of seeds per plot and
flowering age. The results of the study showed that the treatment of coffee leaf
waste 9 kg/plot actually improved almost all of the observed variables except in
flowering age. Treatment of NPK 20 g/real planting hole improved all observed
variables. The combination of treatment of coffee husk waste 9 kg/plot and NPK
20 g/planting hole was the best combination in improving all observed variables76 PagesSkripsi Sarjan
Analysis of Fruit Peel Waste as a Source of Electrical Energy
No full textThe increasing need for electricity can also be seen from many remote villages that have not received electricity for 24 hours. Alternative electricity is environmentally friendly and renewable. The use of fruit peel waste has the potential as an alternative energy source through a fermentation process. This study uses a Complete Randomized Design (CRD) factorial consisting of 2 treatments. The first treatment is a variation of types of fruit peels (P) which consists of P1 = Banana peels, P2 = Pineapple peels, and P3 = Lime peels. The second factor is the variation in fermentation duration consisting of F1 = 8 days, F2 = 10 days, and F3 = 12 days. The research results show that the variation in the types of fruit skins significantly affects pH, current strength, voltage, power, electrical energy, and the duration the light stays on. The variation in fermentation time significantly affects current strength, voltage, power, electrical energy, and the duration the light stays on, but has no significant effect on the pH of the electrolyte solution. The interaction between the variation of fruit skin types and fermentation time significantly affects voltage, power, electrical energy, and the duration the light stays on, but has no significant effect on current strength and the pH of the electrolyte solution.88 PagesSkripsi Sarjan
The Semantics of Body Parts in Batak Toba Language: A Natural Semantic Metalanguage Study
No full textThe human body is an evident domain for exploring shared universal meanings. However, cross-linguistic investigations reveal significant variations in the extension of human body part terminology, as not all languages categorize the body in the same way. Batak Toba Language (BTL) is spoken by the Batak Toba people around Lake Toba, Samosir Island, North Sumatra, Indonesia. This study examines the semantics of body parts in BTL through the framework of Natural Semantic Metalanguage (NSM) as proposed by Wierzbicka (2007). The objectives of this research are to categorize body parts, analyse and introduce new lexical entries to fill gaps in body part nomenclature, detail the meanings of body part terms, and formulate the semantic typology of body parts in BTL and cross-linguistically. This study employs a qualitative approach, generating descriptive data in the form of written and spoken words from informants, as well as lexical data of body part terms in BTL as spoken by native speakers residing on Samosir Island. Data collection techniques include observation, interviews, and questionnaires. The findings categorize body parts in BTL into three groups: upper body parts, middle body parts, and lower body parts. In body part nomenclature, at least three semantic components are identified: location, shape, and function. Interestingly, no specific term for the Adam's apple exists in BTL. Additionally, the term hurum refers to three distinct body parts-jaw, cheek, and temple while sihotingon refers to both the hip and waist. In the semantic interpretation of body parts, meaning analysis aligns with the origin of body part nomenclature, reflecting seven principles governing cross-linguistic body part organization: (1) Body Universality, (2) Partonomy, (3) Duality, (4) Hierarchy, (5) Topography, (6) Internal Logic, and (7) Orientation. Furthermore, the semantic typology of body parts in BTL and other languages demonstrates similarities in the application of the partonomic principle, consistent with Brown's (2015) theory, as well as the positioning of the face as a reference and viewpoint in spatial concepts. However, sociocultural influences create unique categorizations, leading to considerable variation in semantic extension and referential scope.230 PagesDisertasi Dokto
Implementation Strategy of Knowledge Management to Improve Performance at PT PLN (Persero) UP3 Bukit Barisan
No full textThe rapid changes in the business environment, along with the development of digital technology and the demand for high-quality public services, require organizations like PT PLN (Persero) UP3 Bukit Barisan to manage knowledge effectively. This study aims to analyze the implementation strategy of Knowledge Management (KM) in improving organizational performance by emphasizing the strengthening of collaborative culture, the spirit of mutual cooperation, the use of digital technology, and the empowerment of the younger generation. The research method used is a qualitative descriptive approach with SOAR analysis techniques (Strength, Opportunity, Aspiration, Result) to formulate relevant and impactful KM strategies. Data were obtained through in-depth interviews, observations, and internal document reviews. The Results show that KM implementation strategies, including the integration of internal technology, the development of formal and informal knowledge-sharing practices, and active managerial support, significantly contribute to improving work efficiency, accelerating decision-making, reducing technical errors, and strengthening the quality of human resources. In conclusion, KM is not only a managerial tool but also a key pillar in building an adaptive work culture and enhancing sustainable organizational competitiveness.117 PagesTesis Magiste