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BULETIN FISIKA
Published by Universitas Udayana
ISSN : 14114690     EISSN : 25809733     DOI : https://doi.org/10.24843/BF
Core Subject : Health, Science,
Astronomy Energy Materials Science & Nanotechnology Medicine & Pharmacology Physics
Aims and Scope Aims The Journal aims to promote the theory and application in the field of physics and to encourage a vigorous dialogue among scholars and researchers worldwide. It presents original research articles, letters, and review articles, and publishes the latest achievements and developments in physics and related fields. All contributions shall be rigorously refereed and selected based on the quality and originality of the work as well as the breadth of interest to readers. Accepted papers will immediately appear online. The Journal welcomes contributions that the manuscript is written in Indonesian or English. Scope The scope of this journal covers pure and applied physics. The topics include advanced material, optoelectronics, laser applications, biophysics, medical physics, instrumentation, geophysics, environmental physics, and related fields.
Arjuna Subject : Fisika dan Astronomi - Fisika dan Astronomi (Lain-Lain)
Articles 62 Documents
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Crystallographic Evolution of La0.7Ca0.3-xKxMnO3 (0 ≤ x ≤ 0.09) and Its Implications for Magnetocaloric Materials IGA Adnyana; Komang Ngurah Suarbawa; Ni Putu Yuni Nurmalasari; Mashadi Mashadi; Yunasfi Yunasfi; Wisnu Ari Adi
BULETIN FISIKA Vol. 28 No. 1 (2027): BULETIN FISIKA
Publisher : Departement of Physics Faculty of Mathematics and Natural Sciences, and Institute of Research and Community Services Udayana University, Kampus Bukit Jimbaran Badung Bali

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24843/BF.2027.v28.i01.p06

Abstract

Magnetic refrigeration utilizing the magnetocaloric effect (MCE) is becoming a sustainable option compared to conventional gas-compression cooling technologies. In this study, the structural properties of potassium-doped La0.7Ca0.3-xKxMnO₃ (x = 0.01, 0.03, 0.05, 0.07, and 0.09) polycrystalline materials were investigated to assess their potential for magnetocaloric applications. The samples were synthesized via wet mechanical milling followed by sintering at 1000 °C, using high-purity La2O3, CaCO3, K₂CO₃, and MnCO3. X-ray diffraction (XRD) served as a technique for structure analysis, and the Rietveld method played a role in the refinement process. The results showed that single-phase perovskite structures with orthorhombic symmetry (Pnma space group) were successfully formed for all compositions up to x = 0.07, whereas the x = 0.09 sample exhibited a secondary CaO phase. The increase in K⁺ levels caused the unit cell volume to grow, mainly due to the lengthening of the a-axis, while the b and c dimensions saw a reduction. Crystallinity also improved with increasing K content up to x = 0.07. These crystallographic modifications suggest potential implications for magnetocaloric behavior, although direct measurements were not performed.
Design and Development of an IoT-Based Real-Time Monitoring and Spatial Mapping System for Temperature and Light Intensity to Evaluate Reading Room Comfort Abdul Muid; Fiqkri Putra Riswanda
BULETIN FISIKA Vol. 28 No. 1 (2027): BULETIN FISIKA
Publisher : Departement of Physics Faculty of Mathematics and Natural Sciences, and Institute of Research and Community Services Udayana University, Kampus Bukit Jimbaran Badung Bali

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24843/BF.2027.v28.i01.p08

Abstract

Thermal and lighting conditions are important parameters affecting reading comfort, particularly in tropical buildings where external heat loads and building openings may cause non-uniform environmental conditions. This study evaluates the spatial distribution of air temperature, relative humidity, and illuminance in the reading room of the West Kalimantan Library using an Internet of Things (IoT)-based monitoring system. The system was developed using an ESP32 microcontroller integrated with DHT22 and BH175 sensors to measure temperature, relative humidity, and illuminance. Real-time data acquisition and transmission were conducted using the Message Queuing Telemetry Transport (MQTT) protocol. Measurements were performed at 20 observation points to characterize the spatial variability of indoor environmental conditions. The collected data were visualized through spatial distribution maps using the Inverse Distance Weighting (IDW) interpolation method and three-dimensional surface plots. The results showed that the average air temperature was 26.7 °C, which remained within the specified thermal comfort range. However, the average relative humidity of 72% indicated relatively high humidity conditions. Illuminance showed substantial spatial non-uniformity. Areas near windows recorded illuminance levels exceeding 800 lux, which may cause glare, whereas approximately 70% of the reading room area had illuminance levels below 200 lux. These findings indicate that the existing cooling and lighting systems have not provided homogeneous environmental conditions throughout the reading room. The developed IoT-based monitoring and spatial mapping system can serve as an effective evaluation tool for assessing indoor environmental conditions and supporting improvement strategies for cooling and lighting systems.

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