Multi-objective Bayesian topology optimization of a lattice-structured heat sink in natural convection

Additive manufacturing (AM) has an affinity with topology optimization to think of various designs with complex structures. Hence, this paper aims to optimize the design of a lattice-structured heat sink, which can be manufactured by AM. The design objectives are to maximize the thermal performance of convective heat transfer in natural convection simulated by computational fluid dynamics (CFD) and to minimize the material cost required for AM process at the same time. The lattice structure is represented as a node/edge system via graph theory with a moderate number of design variables. Bayesian optimization, which employs the non-dominated sorting genetic algorithm II and the Kriging surrogate model, is conducted to search for better designs with the minimum CFD cost. The present topology optimization successfully finds better lattice-structured heat sink designs than a reference fin-structured design regarding thermal performance and material cost. Also, several optimized lattice-structured designs outperform reference pin-fin-structured designs regarding thermal performance though the pin-fin structure is still advantageous for a material cost-oriented design. This paper also discusses the flow mechanism observed in the heat sink to explain how the optimized heat sink structure satisfies the competing design objectives simultaneously.

Analisis Perbandingan Biaya Perawatan (Cost of illness Stroke Iskemik dan Stroke Hemoragik Pasien Rawat Inap di SUD Pannembahan Senopati

Stroke termasuk dalam penyakit katarostropik yang dapat mengancam jiwa, dan memiliki resiko tinggi serta membutuhan pertolongan segera. Stroke dapat menyebabkan penderitanya memiliki faktor resiko morbiditas seusia hidupnya yang dapat menimbulkan Burden disease sehingga menyebabkan kematian, cedera, hilangnya produktifitas dan membutuhkan biaya penanganan yang cukup tinggi. Tujuan utama dari penelitian ini adalah untuk mengetahui total biaya perawatan dan selisish biaya perawatan stroke iskemik dan stroke hemoragik pasien rawat inap di RSUD Panembahan Senopati Bantul. Penelitian ini menggunakan rancangan penelitian deskriptif analitik non-eksperimental dengan pendekatan cross sectional study menurut perspektif penyedia layanan kesehatan (provider). Biaya yang diperhitungkan adalah biaya langsung (direct cost) menggunakan pendekatan bottom up. Subyek penelitian adalah semua pasien stroke rawat inap yang terdaftar sebagai pasien umum di rumah sakit yang memenuhi kriteria inklusi. Data dianalisis menggunakan software Excel dan SPSS. Hasil penelitian melibatkan 50 sampel yang terdiri dari 32 pasien stroke iskemik dan 18 pasien stroke hemoragik menunjukan dengan analisis regresi linear variabel bebas berpengaruh terhadap biaya stroke sebesar 49,1%. Lama rawat inap menjadi faktor yang paling berpengaruh terhadap tingginya biaya dengan nilai p 0,00 (<0,05). Total direct health cost perawatan stroke adalah sebesar Rp151.633.600,00 Sedangkan material cost sebesar Rp113.954.918,00. Total rata-rata biaya stroke iskemik Rp4.625.511.006, stroke hemoragik Rp6.531.786.277 dengan selisih Rp1.906.275.271.

Utilization of Waste Glass Powder and Glass Composite Fillers in Asphalt Pavements

Today, researchers around the globe are looking for suitable alternatives of conventional fillers which can form flexible pavements with satisfactory engineering performance in an environmental friendly and cost-effective manner. This study investigated the engineering, economical, and environmental viability of recycling waste glass powder (GP) and glass-hydrated lime (GL) composite as alternative fillers, in place of stone dust (SD). All fillers were characterized, and asphalt concrete mixes incorporating them at different proportions (4–8.5%) were designed using the Marshall mix design method. The engineering performance of asphalt mixes was analyzed using the static creep analysis, indirect tensile fatigue test, Cantabro test, modified Lottman test, resilient modulus test, mixing time analysis, and boiling water test. Additionally, the design of single km of two-lane flexible pavements utilizing aforesaid mixes was done as per the mechanistically empirical method suggested in IRC 37 guideline. Finally, the economic and environmental analysis was done by comparing their material cost and global warming potential (GWP). GL and GP mixes exhibited better resistance against rutting, fatigue, and low temperature cracking at lower optimum asphalt content than SD mixes. However, GP mixes also displayed poor moisture resistance and adhesion due to the high amount of silica in GP. GL mixes had satisfactory moisture resistance up to 7% filler content due to the fine nature and anti-stripping properties of hydrated lime. The pavement containing GL and GP fillers also reduced material cost and GWP up to 35% while consuming up to 74 tons of GP.

Evaluation of polyvinylpyrrolidone as draw solute for desalination forward osmosis systems

In this study, polyvinylpyrrolidone (PVP) was evaluated as a potential draw solute for desalination forward osmosis (FO) systems. The effect of various draw solute and draw solution parameters on the efficiency of FO operation was investigated, including PVP molecular weight, PVP concentration in solution, and the salinity of feed solution. Experiment results showed that at draw solution initial concentration of 200 g/L and feed solution initial salinity up to 15 g/L, the PVP-based draw solution can offer water flux up to 14.23 LMH in FO mode with raw material cost only at 0.61 USD/m3. PVP K17 was proven to be an effective draw solute for FO systems, providing good water flux and low reverse draw solute flux; while also being relatively non-toxic, non-corrosive, cheap and widely available compared to other types of novel draw solutes.

PENGARUH RAW MATERIALS COST DAN DIRECT LABOR COST TERHADAP COST OF PRODUCTION PADA UMKM DI KOTA BATAM

The purpose of this study was to find out whether the cost of raw materials and direct labor costs had an effect on the increase in production. In this quantitative research two types of variables are used, namely the independent variable is Raw Material Cost, Direct Labor Cost and the dependent variable is Increased Production Results. Sampling is done by the technique used, namely purposive sampling. Data analysis using Classical Assumptions and Multiple Linear Regression methods. The results of the study were processed using SPSS 20, it can be seen that the Raw Material Cost has a tcount of 4.616 with a significance probability of 0.000, concluded that Raw Material Costs partially have a positive and significant effect on Increasing Production Cost of Direct Labor Costs has t count of 4.944 with a significance of 0,000 can be concluded that Direct Labor Costs partially have a positive and significant effect on Increasing Production Results. The F test shows the Fcount value of 71,270 and significance of 0,000b means that there is a significant effect between Raw Material Costs and Direct Labor Costs on Increasing Production Results.

Material Cost Optimization and Quality Control Improvement of Building Construction

A building construction project cannot be completed successfully by only planning and scheduling. Project controlling that consists of project monitoring and updating, is the other critical stage. Construction materials cost and quality are becoming a severe problem in Ethiopia, especially in Ambo Town, where little consideration is given. The study tried to evaluate different factors affecting the materials cost and quality on building construction site, rank significant factors that are prevalently affecting the cost and quality of materials used for building projects from the point of view of the respondents and established a model to optimize materials cost and materials quality using multilinear regression method to come up with the model best fit. Purposive sampling was used, and 180 questionnaires were administered on building construction firms to analyze Material cost Optimization and quality control Improvement- Case Study of Ambo Town. To achieve this, a questionnaire survey containing factors affecting Building construction material cost and quality, which were identified by literature and Interview, was analyzed by using the Relative Importance Index, Pearson's correlation, and Multilinear regression model. Variables are statistically significant at 95% confidence level is assessed that all of the independent variables are positively related to Building Construction material cost and quality. The RII results showed that Material Wastage minimization (RII = 0.908), Proper workmanship (RII= 0.859), Sufficient Training of workers/staff (RII = 0.876), Proper forecasting of materials price in the market (RII = 0.850), Using suitable, safe and secure storage (RII = 0.886), Quality checking for each delivery of the aggregates to the site (RII = 0.889), Cutting of materials ( glass, tiles, plywood) (RII = 0.870) and Design changes (RII = 0.770) were ranked as the most significant among factors affecting building construction materials. Also, Two Multiple linear regression models were established for both dependent variables (material cost and material quality). The analysis results showed all independent variables were significant and had a strong positive relationship with dependent variables. The values of R2 for the developed equations indicated 0.771 for material cost, and 0.777 for material quality. Hence, the basic recommendations such as planning and monitoring construction activities and inspection and verification of materials were anticipated to be exercised by key role players of the construction industry.