In X-ray fluorescence (XRF), an electron can be ejected from its atomic orbital by the absorption of a light wave (photon) of sufficient energy. The energy of the photon (h?) must be greater than the energy with which the electron is bound to the nucleus of the atom. When an inner orbital electron is ejected from an atom (middle image), an electron from a higher energy level orbital will be transferred to the lower energy level orbital. During this transition a photon maybe emitted from the atom (bottom image). This fluorescent light is called the characteristic X-ray of the element. The energy of the emitted photon will be equal to the difference in energies between the two orbitals occupied by the electron making the transition. Because the energy difference between two specific orbital shells, in a given element, is always the same (i.e. characteristic of a particular element), the photon emitted when an electron moves between these two levels, will always have the same energy. Therefore, by determining the energy (wavelength) of the X-ray light (photon) emitted by a particular element, it is possible to determine the identity of that element.
For a particular energy (wavelength) of fluorescent light emitted by an element, the number of photons per unit time (generally referred to as peak intensity or count rate) is related to the amount of that analyte in the sample. The counting rates for all detectable elements within a sample are usually calculated by counting, for a set amount of time, the number of photons that are detected for the various analytes' characteristic X-ray energy lines. It is important to note that these fluorescent lines are actually observed as peaks with a semi-Gaussian distribution because of the imperfect resolution of modern detector technology. Therefore, by determining the energy of the X-ray peaks in a sample's spectrum, and by calculating the count rate of the various elemental peaks, it is possible to qualitatively establish the elemental composition of the samples and to quantitatively measure the concentration of these elements.
X-ray tube excitation
Like the formerly common vacuum tubes, X-ray tubes are comprised of a cathode - which emits electrons into the vacuum - and an anode to collect the electrons, thus establishing a flow of electrical current through the tube. A high voltage power source, for example 4 to 150 kilovolts (kV), is connected across cathode and anode to accelerate the electrons to impact the anode. The X-ray spectral output of an X-ray tube, which includes both characteristic lines from the anode material and Bremsstrahlung radiation, depends on the anode material and the accelerating voltage.
A common service or repair item, X-ray tubes must be replaced periodically for a variety of reasons, including: broken filament, pitted anode (spectral purity), current leakage, and vaccum loss.
Radioisotope source excitation
Made of encapululated artificially created isotopes of various elements, radioisotope sources have the advantage that they do not need a supply of electrical power to function and are semi-monochromatic, but they also have the enormous disadvantage that they can not be switched off. Because of the obvious safety issues associated with any intrinsically radioactive material, and the threat posed by the potential misappropriation and weaponization of radioactive sources - such as Iron-55 (55Fe), Cadmium-109 (109Cd), Cobalt-57 (57Co), Americium-241 (241Am), and Curium-244 (244Cm), use of radioisotopes has fallen out of favor for use in EDXRF, XRF, and XRT spectrometers and related gauges.
A common service or repair item, radioisotope (RI) sources - as used in ASOMA or SPECTRO gauges - must be replaced if the activity falls to the point where the analytical results are no longer satisfactory due to poor counting statistics. Leakage from, or breach of, source capsule also requires source replacement and/or source disposal.
Proportional counter EDXRF detectors
A proportional counter (PC) is a type of gaseous ionization detector - it works on the same principle as the Geiger-Müller counter, but uses a lower operating voltage. An inert gas is used to fill the tube, with a quench gas added as a stabilizer. A common proportional gas mixture is 90% argon, 10% methane, known as P-10. An incoming photon liberates electrons from the atomic orbitals of the gas atoms, leaving an electron and positively charged atom, commonly known as an ion pair. As the charged particle travels through the chamber, it leaves a trail of ion pairs along its trajectory. The electrons created in this process drift toward a readout electrode, known as the anode, under the influence of an applied electric field. At the same time, the positive ions drift towards the cathode, at much lower speed.
A proportional counter differs from an ionization chamber in that the operating voltage high enough that the drifting electrons gain enough energy over a mean free path to create further ion pairs as they collide with other neutral atoms of the gas. Thus, a cascade of ion pairs (Townsend avalanche) is created. If the operating voltage is chosen correctly, each avalanche occurs independently of others from the same initial event. Therefore, even though the total number of electrons liberated can increase exponentially with distance, the total amount of charge created remains proportional to the amount of charge liberated in the original event. By measuring the total charge (time integral of the electric current) between the electrodes, the initial photon's energy can then be measured.
Another common service or repair item for ASOMA and SPECTRO benchtop EDXRF analyzers, sealed proportion counter (PC) detectors suffer performance degradition after a finite number of events have been recorded. In addition to simply wearing out, beryllium window breakage, loss of resolution, or a compromised enclosure require replacement.
Lithium drifted silicon detectors, for EDXRF spectrometric analysis, essentially consist of a specially treated and manufactured 3-5 mm thick silicon cylinder (junction type p-i-n diode) with a bias of about -1000 V across the two flats. The lithium-drifted center forms the non-conducting intrinsic layer. When an x-ray photon passes through, it causes a specific number (depending on the photon energy) of electron-hole pairs to form, which causes a voltage pulse. To obtain sufficiently low conductivity, the detector must be maintained at low temperature, with liquid nitrogen (LN2) being employed for best resolution. With some loss of resolution, the much more convenient Peltier cooling can be employed.
Si(Li) detectors, as used in ASOMA and SPECTRO spectrometers, are a high maintenance item because most such detectors employ liquid nitrogen cooling. Forgetting to refill the Dewar in a timely manner, to the point where the detector warms up to room temperature, almost always results in some loss of resolution. The resulting resolution degradation may impact analytical performance to the point where the Si(Li) detector requires either refurbishment or replacement. Other factors necessitating service or repair include: loss of vacuum, microphonics, loss of resolution, window contamination and window failure.
PIN-diode EDXRF detectors
A PIN-diode is a diode with a wide, lightly doped 'near' intrinsic semiconductor region between a p-type semiconductor and an n-type semiconductor regions. Peltier cooled silicon PIN photodiodes are commonly employed as high resolution energy dispersive detectors for X-ray fluorescence (XRF)spectrometry. The detection efficiency is a function of the thickness of the silicon wafer; for example, a wafer thickness of 300 microns provides nearly 100% detection efficiency at 10 KeV but only about 1% efficiency at 150 KeV.
While robust in nature, ASOMA and SPECTRO sourced PIN-diode EDXRF detectors do require service or repair whenever the vacuum can is compromised, the Peltier stack stops cooling correctly, the X-ray window is damaged or contaminated, or the PIN-diode degrades due to radiation damage.
A new category of Peltier cooled X-ray detectors, silicon drift detectors (SDD), are chiefly used in X-ray spectrometry (EDXRF and MDXRF) as well as electron microscopy (EDX). This technology has become very popular because their characteristics, compared with other x-ray detectors, include very high count rates and comparatively high energy resolution. Like other solid state x-ray detectors, silicon drift detectors measure the energy of an incoming photon by the amount of ionization it produces in the detector material. The major distinguishing feature of an SDD is a transversal field generated by a series of ring electrodes that forces charge carriers to 'drift' to a small collection electrode. This 'drift' concept of the SDD allows for throughput up to 1,000,000 counts per second (CPS).
Current generation ASOMA and SPECTRO SDD EDXRF detectors, with the field effect transistor (FET) moved out of the radiation path, are far more reliable than the first generation devices. Nevertheless, service or repair is required whenever the vacuum can is compromised, the Peltier stack stops cooling correctly, the X-ray window is damaged or contaminated, or the SDD degrades due to radiation damage.
Pulse processor and multi channel analyzer
Pulses generated by high resolution X-ray detector are processed by pulse-shaping amplifiers (pulse processor). As it takes time for the amplifier to shape the pulse for optimum resolution, there is necessarily a trade-off between resolution and count-rate. Long processing times deliver better resolution but can result in "pulse pile-up" in which the pulses from successive photons overlap. Current state-of-the-art digital pulse processing techniques rely on linear filtering methods which attempt to reduce the pulse length to improve detector performance. However the inability to resolve closely
spaced pulses means pulse pile-up remains a problem. This results in limited detector throughput, decreased spectral accuracy and energy resolution, increased spectral noise, and detector dead time.
In EDXRF, the multichannel analyzer (MCA) is the component used to store information from the pulse processor. Each channel corresponds to a small energy increment and each pulse from the detector is stored in the appropriate channel according to the amplitude of the pulse (that is, the photon energy).
EDXRF spectrometers are the elemental analysis tool of choice, for many applications, in that they are smaller, simpler in design and cost less to operate than other technologies like inductively coupled plasma optical emission spectroscopy (ICP-OES) and atomic absorption (AA) or atomic fluorescence (AF) spectroscopy. Examples of some common EDXRF applications are: Cement and raw meal: sulfur, iron, calcium, silicon, aluminum, magnesium, etc; Kaolin clay: titanium, iron, aluminum, silicon, etc; Granular catalysts: palladium, platinum, rhodium, ruthenium, etc; Ores: copper, tin, gold, silver, etc; Cement and mortar fillers: sulfur in ash; Gasoline, diesel and RFG: sulfur, manganese, lead, etc; Residual gas oils: sulfur, chlorine, vanadium, nickel, etc; Secondary oil: chlorine, etc; Kerosine, naphtha: sulfur, etc; Crude oil and bunker fuels: sulfur, vanadium, nickel, etc; Plating, pickling & pre-treatment baths: gold, copper, rhodium, platinum, nickel, sulfates, phosphates, chlorides, etc; Acetic acid: magnesium, cobalt and bromine; Terephthalic acid (TPA): cobalt, manganese, iron, etc; Dimethyl terephthalate (DMT): heavy metals; PVC copolymer solutions: chlorine; Photographic emulsion: silver; Clay: metals and non-metals; Waste and effluent streams: RCRA metals, chlorides, phosphates, etc; Food, pet food and other animal feed: potassium, phosphorus and chlorine; Cosmetics: zinc, titanium, calcium, manganese, iron, silicon, phosphorus, sulfur, aluminum, and sodium; Wood treatment: CCA, Penta, ACQ, ACZA, phosphorus-based fire retardants, copper naphthanate, zinc napthanate, TBTO, IPBC and combinations of these; Antacids: calcium; and Toothpaste: phosphorus and tin.
Many shippers assume that their transported goods are covered by their freight forwarding company in case of accidents. They believe that as long their cargo is safely loaded into the aircraft or ship, they are already in safe hands. But for those who have learned their lesson the hard way, transporting your cargoes without insurance is a huge financial threat.
What Is Cargo Insurance
Legally, carriers should offer a minimum amount of insurance, which they call carrier liability. Therefore, you can somehow claim a certain percentage of your cargo’s worth from your freight forwarder in case of damage, loss or theft while your goods are in transit. Generally, the cargoes are insured while they are stored and while in transit until they reach the destination.
Unfortunately, not all realize the importance of insurance. This is, in fact, the most important part of freight forwarding and a critical element to have when you want to find an efficient supply carriage shipper that can ship your goods to and from Singapore. A reliable forwarding agent will include a cargo insurance to their package to give clients peace of mind while their cargo is in transit.
What Are the Limitations
As expected, insurances have limitation. For example, when your goods are shipped here in Singapore via truck, the carrier liability does not provide a protection against damages or losses caused by an independent motor carrier. That is why it helps a lot if your air freight, sea freight and local freight comes from a single freight forwarding company. It lets you get an insurance policy that can provide a broader coverage. However, commonly, there is not a single insurance policy you can buy and get 100 percent protection.
There are various types of insurance policies for cargo shipments, some are labeled as ‘broad form,’ ‘allrisks,’ and ‘legal liability.’ Regardless of the name, none of these policies provide total protection. These policies provide coverage in different ways, such as only these certain types of goods are covered, losses caused by some events are not included or a coverage only applied if the service is performed in a particular way.
In general, it is important for any shipper to record the value of their cargo in case of losses, damages or any disputes. It is also critical to seek legal help and work with an insurance company here in Singapore to fully understand your rights and level of protection.
Types of Cargo Insurance
Insurance policies for cargo shipping can be taken for local and international freight. However, it can be challenging to control and standardize any insurance policy without the cooperation of the countries due to the variations of the insurance, which can be categorized into the following classifications:
- Marine Cargo Insurance
This covers the transportation of goods via sea freight. To dispatch goods delivery by ships, whether for import to or export from Singapore, they are covered with insurance in case of damage due to loading and unloading of cargo, piracy, weather contingencies and other issues. Most of these policies cover international freight, but many sea cargo insurances provide them with specific terms and agreements, which vary from provider to provider.
This insurance will protect your cargo from the damages incurred during the land transportation of goods. The insurance’s coverage aspects include collision damages, theft and other related risks. This insurance is a domestic type and, therefore, operates within the boundaries of Singapore.
Why Do You Need It
Your freight forwarding services will have to ship your goods in land, sea and air. Have them insured to protect them against these favorable conditions:
- Damages Caused By Many Different Circumstances
The logistics for transportation of goods provides plenty of opportunities for your cargo to get damaged. Some of the common reasons for damage are:
- Poor packaging
- Wrong choice of container
- Poor distribution of cargo weight
- Lack of carriage instruction
- Wrong temperature
- Stack weight exceeded
- Contaminated floors
There are actually more things that can possibly go wrong and damage your goods. These are just a few to help you see why you need to get your cargo insured.
- Limited Coverage of Carrier Liability
Your freight forwarder only covers so much. Although Freight Master is a trusted name in Singapore for logistics services, it is still imperative to get your grounds covered in case of unforeseen circumstances. Since carrier liability is very limited, you want something that will reimburse the most value of your goods in the event of damage, loss or theft.
Cargo theft, especially in the form of unauthorized pickup, is surprisingly common in this industry. A shipping company cannot monitor every single person who picks up a cargo, so you would want to do your part to help secure your goods and ensure they arrive to the recipient safely.
General Average is an accepted international regulation where in if certain types of accidents happen to the cargo vessel of your logistics company, all entities share in the loss equally. Even if your cargo is safe and undamaged, you will be required to pay a deposit or a bond for the release of your cargo. By getting an insurance, your insurance company will take care of this responsibility and ensures the safe release of your cargo during a General Average situation.
Should I Request for a Cargo Insurance
Now that we have tackled what cargo insurance is, what it covers and why you should get it, hopefully, you have realized the monetary security it can offer to you. If not, think of the possible risks you may encounter in the shipping of your cargo via air freight, sea freight and local freight. What could possibly happen to your business if the entire vessel of your shipping company faced a tragic accident that resulted to the loss of cargoes?
Accidents happen; so, it would be best to ask your logistics company if they offer additional coverage for their insurance. If not, look for an insurance company that can offer you the best possible coverage.
Determining which type of air conditioning system is best for your home or office is crucial if you want to save money on electric bills. Some systems are also compatible with specific setups, but the more complicated air conditioning options for commercial and industrial buildings will need the expertise of the best aircon servicing company in Singapore. Proper installation is the key to maintaining a fully-functioning air conditioning system that is not prone to a lot of problems.
Types of Air Conditioning Systems
• Window – As the name implies, a window-type air conditioner is installed in a window of a room to cool a small space. Your aircon technician in Singapore will recommend this type of aircon if you only need to cool one small room. It is designed to emit warm air at the back and blow cool air into the room.
• Split – Also called mini-split or ductless, this type or air conditioner is ideal for homes with four or less rooms that need cooling. It’s like a mini version of central air conditioning but the systems are interconnected to one outdoor unit and you can adjust the temperature in each individual room. The aircon servicing company will also recommend this type of system to small offices with less than five rooms.
• Packaged – The aircon servicing company will recommend this if you need to cool two large rooms in your office. This can be done in the following ways: the condenser and compressor are placed in one casing but the cooling coil and the expansion valves are placed in different locations; or the compressor, expansion valve, condenser, and evaporator are all placed in one box while the cool air passes through the ducts found in several rooms.
• Centralized – Central air conditioning is ideal for large homes and offices because it cools several rooms efficiently through its supply ducts on the walls and floors. It has a huge compressor capable of producing a hundred tons of cool air. Installation of this type of air conditioning system is complicated and it needs regular aircon maintenance as well. The supply and return ducts must be regularly inspected and the aircon repair will cost more than in other air conditioning systems.
• Portable – This is a smaller, lighter version of the window air conditioner. They are also easy to install, affordable, and are designed to cool only one room, such as a small apartment. Your aircon technician in Singapore will recommend this if you need an affordable option. The unit works by taking the air inside the room, cooling it, and blowing it back to the room.
• Hybrid – You can find this type of air conditioner in most cars, because it uses energy from both fossil fuels and electricity to cool the air. This might also be useful in large industrial facilities that use heavy equipment. Aircon repair is more complicated than the other types of aircon, that is why regular aircon maintenance is a must.
Proper Installation of Residential Aircons
If you have just moved in to a new apartment in Singapore, call the nearest aircon servicing shop to perform an inspection and maintain cooling ventilation system in your Singapore residence. If the system is not centralized, then you need to determine if the existing ventilation system in building will meet your needs. For small apartments with less than five rooms, you can save more money with a window, portable or split aircon.
Look for energy-efficient models that are easy to install and maintain. The aircon maintenance crew can tell you if the type of aircon you have in mind will be enough for the size of the area. Besides the area, the aircon technician will also consider the condition of the area where the exterior parts of the aircon will be installed, the direction of the sunlight if it is a window aircon, the noise produced by the unit, and the space for the refrigeration line if it is a split aircon.
A ductless aircon is slightly more complicated to install than the portable and window aircons, because it needs specific measurements and sizing. Only a reputable aircon servicing company in Singapore should install this to avoid problems in the future.
To avoid issues, you must schedule a regular maintenance with the same aircon servicing company that installed the system.
Proper Installation of Commercial/Industrial Aircon Systems
Offices must consider the following factors when choosing an air conditioning system: budget, area or spaces that need air conditioning, the condition of the walls and ceiling, energy-efficiency, the condition of the area where the exterior units will be placed, and the heat generated by the system.
A packaged air conditioner for example has two units, one for the evaporative process and another for the cooling process. This type of aircon must be installed in an external wall and connected to the other components of a HVAC or heating, ventilation, and air conditioning systems found in most buildings.
The central air conditioning system is the most popular choice in most buildings, however, because it is energy-efficient and does not produce a lot of noise. For this type of aircon, it needs two distinct units that are connected by the refrigerant tubing. Extensive planning and layout is required before this system is installed. To best determine the correct size for the central air conditioning, consult a licensed aircon technician who will survey the space. Remember that for the system to work, it must always have two components, the evaporating unit and the condensing unit.
Regular aircon maintenance is also crucial for central air conditioning because the ducts must be cleaned and inspected, the filters replaced, and the thermostat calibrated.
Private investigators are hired for many different reasons, including security purposes, surveillance works, to find missing witnesses and persons, background checking, accident reconstructions and even to catch cheating spouse. The investigator you hire plays a significant role for the success of the investigation.
For instance, if the investigation is done for a criminal case, a good private investigator can potentially turn the tables. So, what can you do to ensure that the PI you hired is going to be worth it? Here are the key considerations to keep in mind when looking for a private investigator.
Here in Singapore, it is mandatory for legal private investigators to get a license. To be able to secure one, investigators need to undergo training, have considerable experience and has to undergo thorough background check. Therefore, a licensed PI is likely to have better skills and more experience, and has better understanding of the ethical matters involved in the compliance of the duty.
Upon meeting, ask the investigator to provide his license number, and then have it verified in the licensing agency to check whether the investigator is a licensed PI in Singapore.
While investigators offer a wide range of private investigator services, most of them specialize in specific investigative fields. Some PIs have undergone formal training. Some might have work experience that lead to certain investigative jobs, such as being once an arson investigator, a police officer or an insurance investigator. The more experience and training an investigator have undergone that is relevant to his work, the more likely the expert is going to perform private investigator services competently.
In addition, a trained private investigator in Singapore is less likely to commit mistakes that can hamper the progress of the case, such as violating client confidentiality or taking investigative works that causes conflict of interest. A well-experienced expert within a particular field is also able to utilize resources and knowledge that may not be known to less qualified PIs.
Before finally hiring a potential investigator, make sure to interview them. After all, you would not expect getting a job without an interview, and this is not an exemption. Here are a few of the most important questions to include in an interview.
• What is your background of this job?
Asking this question will give you a general idea of their expertise. Are they retired police officer? Have worked in FBI? Other than knowing their work history, it helps you find out that they are retired officers, not fired officers. Termination from being a law enforcer could be due to poor performance or as serious as unethical or illegal practices—the information you must know before employing private investigator services.
• Who will be assigned for my case?
In order for an investigative firm to provide excellent quality service, they assign a team of investigators, each with different skills, backgrounds and experience in order to handle a case the best way possible. For such reason, find out the capabilities of every individual in the team and determine their strengths that can help in the successful investigation of your case. However, do not get offended if your case is not handled by the head investigator. Different experts in the organizations have specific sets of skills and contact that can help for the accurate and fast resolution of your case. Trust the experts assigned to you; they are the ones assigned to handle your case for a good reason.
• How long have you been a private investigator?
Like any other profession, before becoming a pro in your field, we have to start somewhere. But having less experience does not mean they are bad. Understand that employing a newer investigator is not a bad thing. However, it is also important to keep in mind that for more delicate matters, like custody cases and professional surveillance, experience is key. Moreover, investigators with excellent success records and practice ethical behaviour are more likely to provide you with great results. Just know, though, that hiring a respectable, qualified and newly licensed PI in Singapore is not bad thing either.
Private Investigator Fees
The fee that your investigator will charge will depend on the nature of the work for which the expert is hired. Some investigative works can be conducted on a fixed rate, such as basic background check or search of digital records for a missing individual. For more thorough investigative works, you are likelt to be charged with a higher rate.
Some investigator services are essentially costly, such as surveillance of a particular individual. As a rule of thumb, the more time an investigator commits to an investigation, the more the service will cost.
Another factor that can affect the pricing of a service is the extent of the expert’s experience, the complexity of the operations and the timeframe you demand. But always keep in mind that whatever arrangement you negotiate regarding the payment, have it stated in the contract. Include in the written agreement when the payment should be given and additional services and tasks included in the fee.
Private investigators are hired by people to find out the truth regardless of what you feel, expect or think about something. If you hire a PI to catch cheating spouse, but turns out after the investigation that they were not, then that is the truth. What you expect as a result of your case is not always what you are going to get after a thorough investigation. A private investigator cannot guarantee to give you the results you want. They can only assure that they will do their job well and provide you nothing but the truth. The outcome of the case? That’s another story.
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