จำนวน Repository ( 34 )

การเลือกฟังก์ชันการแจกแจงความน่าจะเป็นสะสมสำหรับแนวโน้มเพื่อสร้างตัวแบบสำหรับวิเคราะห์ข้อมูลอนุกรมเวลาหลายๆตัวพร้อมกันที่มีค่า อัตตสหสัมพันธ์แนวโน้ม และค่าผิดปกติ ด้วยวิธีของเบย์: กรณีศึกษาราคาหุ้นที่มีความผันผวนของตลาดหลักทรัพย์แห่งประเทศไทย
การเลือกฟังก์ชันการแจกแจงความน่าจะเป็นสะสมสำหรับแนวโน้มเพื่อสร้างตัวแบบสำหรับวิเคราะห์ข้อมูลอนุกรมเวลาหลายๆตัวพร้อมกันที่มีค่า อัตตสหสัมพันธ์แนวโน้ม และค่าผิดปกติ ด้วยวิธีของเบย์: กรณีศึกษาราคาหุ้นที่มีความผันผวนของตลาดหลักทรัพย์แห่งประเทศไทย

The objective of this research is to select a proper cumulative function for trend in an analysis of simultaneous multiple time series data with autocorrelation trend and outliers using a Bayesian method. The proposed model is applied to fluctuate stock price data in the stock exchange of Thailand. The data consist of the closing prices of 5 stocks. The algorithms are written in OpenBUGS and the performance of the model is evaluated via a simulation study in R. The cumulative distribution functions considered here are a Weibull cumulative distribution function and an exponential cumulative distribution. They are compared using RMSE MAPE and MAE as criteria. The research found that an exponential cumulative function for trends gives smaller values of the three criteria in both model fitting and model validation for the4 stocks EA NWR and KTB. However a Weibull cumulative distribution function gives smaller values of three criteria for the PTT in both model fitting and model validation.

2558
Taxonomy and distribution of the plant family Podostemaceae in  Phitsanulok and Phetchabun provinces, Thailand
Taxonomy and distribution of the plant family Podostemaceae in Phitsanulok and Phetchabun provinces, Thailand

Recent explorations of Podostemaceae have discovered 2 new species to science (Dalzellia TWA-216 และ Hydrobryum TWA-198) from Phitsanulok Province and 3 more genera and six more species from previously known (2 genera and 4 species). Totally five genera and 10 species occur in Phitsanulok and Phetchabun provinces. Based on morphological and molecular evidence the taxa are classified into subfamily Tristichoideae including 2 genera and 3 species (Dalzellia 2 spp. and Terniopsis 1 sp.) and subfamily Podostemoideae consisting 3 genera and 7 species (Hanseniella 1 sp. Hydrobryum 5 spp. and Thawatchaia 1 sp.). The species found in both provinces are Hy. phetchabunense and Hy. tardhuangense while D. kailarsenii is found only in Phetchabun. The plants discovered only in Phitsanulok include Dalzellia TWA-216 Hydrobryum TWA-198 Han. heterophylla Hy. bifoliatum Hy. kaengsophense Th. trilobata and T. minor. Among the species found Hy. tardhuangense and Th. trilobata are also distributed to the Lao PDR and the rests are endemic to Thailand.

2558
Grounding system analysis for reduce voltage sag in distribution system
Grounding system analysis for reduce voltage sag in distribution system

The fault in a power distribution system disturbs the power dispatch under normal conditions therefore decreases the quality of the electric power. The single line to ground fault is an asymmetric fault that may have a high percentage chance to happen. The kind of fault changes power and voltage dramatically. The size of the phase voltage decreases which affect the economic damage of the system. This paper presents an analysis of grounding systems to reduce voltage drop in a power distribution system by using the technical analysis system in case of one phase to ground fault. The objective is to minimize voltage drop for users using the simulation with single line to ground fault in distribution system voltage level at 22 kV PEA’s test system. The simulation utilizes the EMTDC-PSCAD program. The results show that the grounding method can reduce the voltage drop and reduce the damage of the economic system

2558
Design and development of calculation program for magnetic fields intensity of high voltage transmission and distribution lines
Design and development of calculation program for magnetic fields intensity of high voltage transmission and distribution lines

This paper presents a program developed for calculating magnetic field intensity of high voltage transmission line and high voltage distribution lines. This program was developed with Microsoft Visual Basic and Microsoft Access program was used to store the database of the peak ratings current height and space of transmission lines. The developed program was able to calculate magnetic field intensity of high voltage transmission line and high voltage distribution lines according to 2 standards of Provincial Electricity (PEA): “A 22 kV Single Conductor Circuit High Voltage Distribution System” and “115 kV Single Conductor Circuit High Voltage Transmission System”. The program was able to select structure of the electrical system to be calculated as well as types and specification of Transmission line from the stored database that corresponded with the structure. The calculated output waveforms were displayed on computer monitor. Results from the developed program enable more convenient and faster calculations of magnetic field intensity of high voltage transmission line and high voltage distribution lines and are useful for analysis of possible impacts on electric and electronic devices.

2558
Distribution and Phytotoxicity of Polycyclic Aromatic
Distribution and Phytotoxicity of Polycyclic Aromatic

Polycyclic aromatic hydrocarbons are a group of important organic pollutants and should be concerned. General sources of PAHs are contamination of petroleum hydrocarbons and incomplete combusion of organic compounds. The recalcitrance of these compounds depends on the arrangment of benzene rings and their molecular weight. Besides they are carcinogenic and mutagenic to animals PAHs show several toxicity to plant such as decreasing shoot and root growth and photosynthetic rate. PAHs are toxic to plant at molecular level such as increasing oxidation pressure and decreasing gene expression of cell wall-loosening protein expansion. Photooxidized PAHs showed higher toxicity to plant than parent compounds. Plant species and some environmental factors such as soil pH affect to PAHs phytotoxicity. Phytotoxiciy of Polycyclic aromatic hydrocarbons to crop plant growing in Polycyclic aromatic hydrocarboncontaminated soil is an important environmental concern

2554