Stash
Subham Bera's Stashed Knowledge
ph measurement
In chemistry, pH (/piːˈeɪtʃ/, denoting 'potential of hydrogen' or 'power of hydrogen'[1]) is a scale used to specify the acidity or basicity of an aqueous solution. Lower pH values correspond to solutions which are more acidic in nature, while higher values correspond to solutions which are more basic or alkaline. At room temperature (25 °C or 77 °F), pure water is neutral (neither acidic nor basic) and has a pH of 7. The pH scale is logarithmic and inversely indicates the concentration of hydrogen ions in the solution (a lower pH indicates a higher concentration of hydrogen ions). This is because the formula used to calculate pH approximates the negative of the base 10 logarithm of the molar concentration[a] of hydrogen ions in the solution. More precisely, pH is the negative of the base 10 logarithm of the activity of the hydrogen ion.[2] At 25 °C, solutions with a pH less than 7 are acidic, and solutions with a pH greater than 7 are basic. The neutral value of the pH depends on the temperature, being lower than 7 if the temperature increases. The pH value can be less than 0 for very strong acids, or greater than 14 for very strong bases.[3] The pH scale is traceable to a set of standard solutions whose pH is established by international agreement.[4] Primary pH standard values are determined using a concentration cell with transference, by measuring the potential difference between a hydrogen electrode and a standard electrode such as the silver chloride electrode. The pH of aqueous solutions can be measured with a glass electrode and a pH meter, or a color-changing indicator. Measurements of pH are important in chemistry, agronomy, medicine, water treatment, and many other applications.
Subham Bera
nmr spectroscopy 1
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique to observe local magnetic fields around atomic nuclei. The sample is placed in a magnetic field and the NMR signal is produced by excitation of the nuclei sample with radio waves into nuclear magnetic resonance, which is detected with sensitive radio receivers. The intramolecular magnetic field around an atom in a molecule changes the resonance frequency, thus giving access to details of the electronic structure of a molecule and its individual functional groups. As the fields are unique or highly characteristic to individual compounds, in modern organic chemistry practice, NMR spectroscopy is the definitive method to identify monomolecular organic compounds. Similarly, biochemists use NMR to identify proteins and other complex molecules. Besides identification, NMR spectroscopy provides detailed information about the structure, dynamics, reaction state, and chemical environment of molecules. The most common types of NMR are proton and carbon-13 NMR spectroscopy, but it is applicable to any kind of sample that contains nuclei possessing spin
nmr spectroscopy 2
NMR spectra are unique, well-resolved, analytically tractable and often highly predictable for small molecules. Different functional groups are obviously distinguishable, and identical functional groups with differing neighboring substituents still give distinguishable signals. NMR has largely replaced traditional wet chemistry tests such as color reagents or typical chromatography for identification. A disadvantage is that a relatively large amount, 2–50 mg, of a purified substance is required, although it may be recovered through a workup. Preferably, the sample should be dissolved in a solvent, because NMR analysis of solids requires a dedicated magic angle spinning machine and may not give equally well-resolved spectra. The timescale of NMR is relatively long, and thus it is not suitable for observing fast phenomena, producing only an averaged spectrum. Although large amounts of impurities do show on an NMR spectrum, better methods exist for detecting impurities, as NMR is inherently not very sensitive - though at higher frequencies, sensitivity is higher
measurement of pressure
Pressure measurement is the analysis of an applied force by a fluid (liquid or gas) on a surface. Pressure is typically measured in units of force per unit of surface area. Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure and display pressure in an integral unit are called pressure meters or pressure gauges or vacuum gauges. A manometer is a good example, as it uses the surface area and weight of a column of liquid to both measure and indicate pressure. Likewise the widely used Bourdon gauge is a mechanical device, which both measures and indicates and is probably the best known type of gauge. A vacuum gauge is a pressure gauge used to measure pressures lower than the ambient atmospheric pressure, which is set as the zero point, in negative values (e.g.: −15 psig or −760 mmHg equals total vacuum). Most gauges measure pressure relative to atmospheric pressure as the zero point, so this form of reading is simply referred to as "gauge pressure". However, anything greater than total vacuum is technically a form of pressure. For very accurate readings, especially at very low pressures, a gauge that uses total vacuum as the zero point may be used, giving pressure readings in an absolute scale. Other methods of pressure measurement involve sensors that can transmit the pressure reading to a remote indicator or control system (telemetry).
level measurement
Level of measurement or scale of measure is a classification that describes the nature of information within the values assigned to variables.[1] Psychologist Stanley Smith Stevens developed the best-known classification with four levels, or scales, of measurement: nominal, ordinal, interval, and ratio.[1][2] This framework of distinguishing levels of measurement originated in psychology and is widely criticized by scholars in other disciplines.[3] Other classifications include those by Mosteller and Tukey,[4] and by Chrisman
extraction
In biology and medicine Comedo extraction, a method of acne treatment Dental extraction, the surgical removal of a tooth from the mouth In computing and information science Data extraction, the process of retrieving data out of data sources The process of reversing data compression, a.k.a. decompression The process of choosing elements from a source document, in linguistics Other uses in science and technology Root extraction, in mathematics, the computation of a nth root Extraction (chemistry), the separation of a substance from a matrix Extraction (firearms), the act of removing a spent cartridge from the chamber of a firearm. Fragrance extraction, the process of obtaining fragrant oils and compounds from raw materials Resource extraction, the process of locating, acquiring and selling any resource Petroleum extraction, the process of recovering petroleum from the ground Ancestry or origin of a person
enhanced distillation
Distillation is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation. Distillation may result in essentially complete separation (nearly pure components), or it may be a partial separation that increases the concentration of selected components in the mixture. In either case, the process exploits differences in the relative volatility of the mixture's components. In industrial chemistry, distillation is a unit operation of practically universal importance, but it is a physical separation process, not a chemical reaction. Distillation has many applications. For example: The distillation of fermented products produces distilled beverages with a high alcohol content, or separates other fermentation products of commercial value. Distillation is an effective and traditional method of desalination. In the petroleum industry, oil stabilization is a form of partial distillation that reduces the vapor pressure of crude oil, thereby making it safe for storage and transport as well as reducing the atmospheric emissions of volatile hydrocarbons. In midstream operations at oil refineries, fractional distillation is a major class of operation for transforming crude oil into fuels and chemical feed stocks.[2][3][4] Cryogenic distillation leads to the separation of air into its components – notably oxygen, nitrogen, and argon – for industrial use. In the chemical industry, large amounts of crude liquid products of chemical synthesis are distilled to separate them, either from other products, from impurities, or from unreacted starting materials. An installation used for distillation, especially of distilled beverages, is a distillery. The distillation equipment itself is a still
micro-reactor
A microreactor or microstructured reactor or microchannel reactor is a device in which chemical reactions take place in a confinement with typical lateral dimensions below 1 mm; the most typical form of such confinement are microchannels.[1] Microreactors are studied in the field of micro process engineering, together with other devices (such as micro heat exchangers) in which physical processes occur. The microreactor is usually a continuous flow reactor[2][3] (contrast with/to a batch reactor). Microreactors offer many advantages over conventional scale reactors, including vast improvements in energy efficiency, reaction speed and yield, safety, reliability, scalability, on-site/on-demand production, and a much finer degree of process control
stability analysis
Slope stability analysis is a static or dynamic, analytical or empirical method to evaluate the stability of earth and rock-fill dams, embankments, excavated slopes, and natural slopes in soil and rock. Slope stability refers to the condition of inclined soil or rock slopes to withstand or undergo movement. The stability condition of slopes is a subject of study and research in soil mechanics, geotechnical engineering and engineering geology. Analyses are generally aimed at understanding the causes of an occurred slope failure, or the factors that can potentially trigger a slope movement, resulting in a landslide, as well as at preventing the initiation of such movement, slowing it down or arresting it through mitigation countermeasures. The stability of a slope is essentially controlled by the ratio between the available shear strength and the acting shear stress, which can be expressed in terms of a safety factor if these quantities are integrated over a potential (or actual) sliding surface. A slope can be globally stable if the safety factor, computed along any potential sliding surface running from the top of the slope to its toe, is always larger than 1. The smallest value of the safety factor will be taken as representing the global stability condition of the slope. Similarly, a slope can be locally stable if a safety factor larger than 1 is computed along any potential sliding surface running through a limited portion of the slope (for instance only within its toe). Values of the global or local safety factors close to 1 (typically comprised between 1 and 1.3, depending on regulations) indicate marginally stable slopes that require attention, monitoring and/or an engineering intervention (slope stabilization) to increase the safety factor and reduce the probability of a slope movement.
X-Ray methods
This article is about the nature, production, and uses of the radiation. For the method of imaging, see Radiography. For the medical specialty, see Radiology. For other meanings, see X-ray (disambiguation). Not to be confused with X-wave or X-band. X-rays are part of the electromagnetic spectrum, with wavelengths shorter than visible light. Different applications use different parts of the X-ray spectrum. X-ray X-ray of human lungs An X-ray, or X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometres to 10 nanometres, corresponding to frequencies in the range 30 petahertz to 30 exahertz (3×1015 Hz to 3×1018 Hz) and energies in the range 124 eV to 124 keV. X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma rays. In many languages, X-radiation is referred to as Röntgen radiation, after the German scientist Wilhelm Röntgen, who discovered it on November 8, 1895.[1] He named it X-radiation to signify an unknown type of radiation.[2] Spellings of X-ray(s) in English include the variants x-ray(s), xray(s), and X ray(s
matlab (for the beginners)
The tutorials are independent of the rest of the document. The primarily objective is to help you learn quickly the first steps. The emphasis here is “learning by doing”. Therefore, the best way to learn is by trying it yourself. Working through the examples will give you a feel for the way that MATLAB operates. In this introduction we will describe how MATLAB handles simple numerical expressions and mathematical formulas. The name MATLAB stands for MATrix LABoratory. MATLAB was written originally to provide easy access to matrix software developed by the LINPACK (linear system package) and EISPACK (Eigen system package) projects. MATLAB [1] is a high-performance language for technical computing. It integrates computation, visualization, and programming environment. Furthermore, MATLAB is a modern programming language environment: it has sophisticated data structures, contains built-in editing and debugging tools, and supports object-oriented programming. These factors make MATLAB an excellent tool for teaching and research. MATLAB has many advantages compared to conventional computer languages (e.g., C, FORTRAN) for solving technical problems. MATLAB is an interactive system whose basic data element is an array that does not require dimensioning. The software package has been commercially available since 1984 and is now considered as a standard tool at most universities and industries worldwide.
matlab
The end of this document contains two useful sections: a Glossary which contains the brief summary of the commands and built-in functions as well as a collection of release notes. The release notes, which include several new features of the Release 14 with Service Pack 2, well known as R14SP2, can also be found in Appendix. All of the MATLAB commands have been tested to take advantage with new features of the current version of MATLAB available here at Northwestern (R14SP2). Although, most of the examples and exercises still work with previous releases as well. This manual reflects the ongoing effort of the McCormick School of Engineering and Applied Science leading by Dean Stephen Carr to institute a significant technical computing in the Engineering First°R 2 courses taught at Northwestern University. Finally, the students - Engineering Analysis (EA) Section - deserve my special gratitude. They were very active participants in class.