The prosperity of the global air freight shipping china depends on the free movement of people and trade. No one can benefit from trade frictions, protectionist policies and isolationist policies. A more inclusive globalization is the way forward for the world.
The International Air Transport Association believes that the global air transport industry will continue to be profitable this year, reaching 10 consecutive years of profitability, but under the influence of many challenges, this year's net profit will be reduced.
In December 2018, the International Air Transport Association predicted that the net profit after tax of the global air transport industry in 2019 will reach 35.5 billion U.S. dollars, but the growth rate has recently been significantly reduced to 28 billion U.S. dollars. Alexander de Juniac, chairman and chief executive officer of the International Air Transport Association, said that rising costs in labor, fuel and infrastructure will directly squeeze profit margins, and Sino-US trade frictions will intensify, and global trade weakness continues. Not only will it directly impact air cargo, it will also slow down passenger growth.
What challenges does the air freight shipping china face this year?
First, the cost of the air transport industry has risen.
Fuel prices remain high in 2018 and will continue to rise this year. It is expected that the fuel cost of the air transport industry as a percentage of operating costs will rise from 23.5% last year to 25% this year.
Second, the demand for air cargo and passenger transport will slow down.
The volume of air cargo in 2018 was 63.3 million tons, and the growth rate of demand dropped significantly from 9.7% in 2017 to 3.4%. Air cargo will continue to be under pressure this year, with cargo volume expected to drop to 63.1 million tons.
Third, the uncertainties in the international situation have increased risks.
International unstable political situations and potential conflicts will increase the operational risks of the air transport industry, and protectionism and unilateralism will also have a negative impact on the air transport industry.
Alexander de Juniac said that the prosperity of the global air transport industry depends on the free movement of people and trade, and no one can benefit from trade frictions, protectionist policies and isolationist policies.
Taken together, the International Air Transport Association estimates that the total expenditure of the global air transport industry in 2019 may reach US $ 822 billion, a year-on-year increase of 7.4%; total revenue may reach US $ 865 billion, an increase of 6.5% year-on-year; the growth rate of expenditure is higher than the revenue Rate, this year's net profit rate may drop from 3.7% last year to 3.2%.
In addition, Ma Tao, vice president of the North Asia Region of the International Air Transport Association, said in an interview with the Economic Daily that China ’s air transport industry has achieved rapid and safe development in recent decades. China ’s experience is worth learning from for the development of the global air transport industry.
There are many types of activated alumina catalysts in exhaust gas treatment, and the classification methods are also different. According to the big aspects, it can be divided into acid-base catalysts, metal catalysts, semiconductor catalysts and molecular sieve catalysts. Their common feature is that they can produce different degrees of chemical adsorption on reactants. Therefore, catalysis is inseparable from adsorption, and the general catalytic process starts with adsorption.
1. Acid-base catalysts referred to here are acids and bases in a broad sense, that is, Lewis acids and Lewis bases. Both of them can provide acid-base active adsorption centers for chemisorption of reactants, thereby promoting chemical reactions.
Such as activated clay, aluminum silicate, aluminum oxide and oxides of some metals, especially oxides of transition metals or their salts.
2. Metal catalyst Metal adsorption capacity depends on the molecular structure and adsorption conditions of the metal and gas. It was found through experiments that metal elements with d-electron empty orbits have different chemical adsorption capacities for some representative gases.
Except for Ca, Sr, and Ba, most of these metals are transition metals. They rely on electrons or unbound electrons that do not participate in the hybrid orbitals of the metal bond to form adsorption bonds with the adsorbent molecules, which catalyzes the interaction between them Reaction.
3. Semiconductor catalysts are mainly some semiconductor-type transition metal oxides. They are divided into n-type semiconductors and p-type semiconductors in order to provide quasi-free electrons or quasi-free holes.
The n-type semiconductor catalyst relies on its quasi-free electrons to form adsorption bonds with the reactants; the p-type semiconductor catalyst relies on its quasi-free holes to form adsorption bonds with the reactants. Due to the formation of adsorption bonds, the conductivity of the semiconductor is changed, which is one of the main factors affecting the activity of the catalyst.
In fact, the formation of adsorption bonds between gas molecules and semiconductor catalysts is a very complicated process. In the study of the catalytic mechanism of semiconductors, it was also found that the energy bands due to electronic transitions play an important role in the formation of adsorption bonds. effect. Therefore, it cannot be simply assumed that a reactant molecule capable of donating an electron can only form an adsorption bond with a p-type semiconductor catalyst.
4. Zeolite molecular sieve catalyst is widely used as an adsorbent in drying, purification, separation and other processes. It began to make its appearance in the application of catalysts and catalyst carriers in the 1960s.
Zeolite refers to the natural crystalline aluminosilicate, which has the same diameter micropores, so it is also called molecular sieve. At present, there are more than hundreds of species, and many important industrial catalytic reactions are inseparable from molecular sieve catalysts.
The catalysis of molecular sieve also relies on acidic centers on its surface to form adsorption bonds. However, it is more selective than acid-base catalysts because it can reject molecules with a larger pore size from entering the inner surface. At the same time, the acidity and alkalinity on the surface of the molecular sieve can also be adjusted artificially by means of ion exchange, which has better performance than ordinary acid-base catalysts.
In recent years, a kind of non-silicon-aluminum-based synthetic molecular sieve has been developed and has been widely used in the field of catalysis. It can be seen that molecular sieve has its special status and role in the field of catalysis.
In a wide range of applications of power supplies, as a professional power supply for LEDs, most of them require a certain waterproof function, and have high requirements for the level of waterproofing. Regardless of whether the requirements are waterproof, but also the ability to adapt to the ambient temperature and the operating conditions of equipment in severe weather have high requirements.
Waterproof power supply must have certain requirements for its insulation and working temperature. The working temperature of the led waterproof switching power supply is generally -40 -80 ° C (outer surface temperature of the case), the storage temperature is -40 -85 ° C, and the working humidity is 10-90% relative humidity.
LED waterproof switching power supply has great requirements for the working environment and has been widely used in daily life. So, what characteristics does it have?
1. High reliability: Especially the driving power sources like LED street lights are at high altitude, so it leads to inconvenience of maintenance, and the cost is even greater.
2. High efficiency: LED is an energy-saving product, and the efficiency of the driving power supply must be high. For the power supply, the structure placed in the led lamp is very important.
The luminous efficiency of LED will decrease with the increase of LED temperature, so the heat dissipation of LED is especially important. When the efficiency of the power supply is high, the power loss of the power supply becomes smaller, the heat generation in the LED lamp will also be reduced, and the temperature of the lamp will be reduced accordingly, which is beneficial to delaying the light decay of the LED.
3. High power: The power factor is the load requirement of the grid. Generally, there are no mandatory indicators for electrical appliances below 70 watts.
4. Driving mode: one constant voltage source provides multiple constant current sources, and each constant current source supplies power to each LED individually. Its advantage is that the combination is flexible, and the failure of all the LEDs will not affect the normal operation of other LEDs, which will be higher for cost.
The second type is direct constant current power supply, and the LEDs are operated in series or in parallel, but there is a obvious disadvantage that it is poor flexibility.
These two forms coexist for a period of time, and multiple constant current output power supply methods will be better in terms of cost and performance.
5. Surge protection function: LED's ability to resist surge is relatively poor, especially its ability to resist reverse voltage. For example, led lamps installed outdoors, due to the start-up of the grid load and the induction of lightning strikes, various surges can be invaded from the grid system, and some surges can cause damage to LEDs. Therefore, the LED drive power must have the ability to suppress the intrusion of the surge and protect the LED from damage.
6. Protection function: In addition to the normal protection function of the power supply, it is best to add negative feedback of LED temperature to the constant current output to prevent the LED temperature from becoming too high.
7. Protection: The type of the lamp is externally installed, the power supply structure should be waterproof and moisture-proof, and the shell should be resistant to sunlight.
8. The life of the drive power must be adapted to the life of the LED.
9. To meet the requirements of safety regulations and electromagnetic compatibility.
LED waterproof power supply supplies are mostly used to provide driving capabilities for various LED lamps, such as LED spotlights, LED street lights, LED underground lights, LED ceiling lights, and LED panel lights. The biggest feature of the led power supply is that it is waterproof and can be used outdoors. At the same time, it is not afraid of bad weather such as rain, fog and direct sunlight.