Dimethyl Ether (DME) is not only an important chemical, but also can be converted into liquefied petroleum gas. Furthermore, DME is also an ideal substitute for diesel or liquefied petroleum gas. So, the application prospect of DME becomes wider. In recent years, the synthesis process of DME has attracted much attention in research fields and industrial field.The syngas, which is produced commercially by steam reforming of natural gas or coal can be converted into DME. As well known, coal resource in China is very rich, production of DME from coal is an important option for the efficient conversion of coal into clean fuel.The conventional process of DME production, named two-step method, has become more and more insufficient with the growing demand for DME as fuels for new applications. Lately, an original technique namedwas developed for the direct synthesis of DME from in a single reactor. Compared with the conventional method, the is attracting more and more industrial attention from industry because of its dramatically economic values and theoretical significance.The directly convert into by using fixed – bed and high – pressure flow apparatus. In this paper, the catalyst and process of from syngas were studied.Firstly, a series of catalysts were prepared with mechanical mixing method. These catalysts were investigated by means of XRD, BET and NH3-TPD. The methanol synthesis catalyst and methanol dehydration catalyst were tested, which resulted in the conclusion that the optimal catalyst is C207/HZSM-5=4:1 (weigh ratio), and the ratio of Si/Al of HZSM-5 is 50.Secondly, the effect of temperature, pressure, space velocity and reduction temperature were discussed, then the optimal reaction conditions were optained: T=275℃, P=5.0MPa, SV=1600h-1, reduced temperature is 300℃. The conversion of the CO is above 90%, the yield of the DME is above 70%.
As thematerial of milk manufacture, the quality control of raw milk is the substantial step in the whole quality control. If this step occurs problems, no matter how advanced the next control method is and how strict the control instrument is, we will only get half the result with twice the effort. Milk is a kind of well-fed food. These nutrition is extremely good for microbe’s growth and reproduction. Therefore, detect raw milk’s aerobic bacterial count is one of the most important indexes of milk quality’s detection. The traditional method of detecting aerobic bacterial count is agar counting which operate fussily, need 48 hours’detect time and count with naked eye can be easily influenced by environmental factors and influence economic efficiency of milk manufacture. In this thesis, research has been done about detecting aerobic bacterial count in the raw milk with homemade impedance detector. Introduce homemade impedance detector’s work principle, tester’s configuration and test parameter’s enactment; analyse the effect of the sample’s cubage, raw milk’s protein content, fat content and aerobic bacterial count on detect result of impedance detector; do research about the change rule of aerobic bacterial count and detect time in raw milk; detect the time when raw milk’s resistance and electromotive force achieve threshold, combine linearity regress theory and method, build linearity regress mathematical model and standard curve of aerobic bacterial count and detect time; make contrast experiment with impedance detector and the method of agar counting to detect aerobic bacterial count in raw milk, make compare analysis to the two results. The main conclusion as follows:(1)The homemade impedance tester is used to detect the bacterial totall of the milk which is placed different days in the room. Checking the electromotive force and resistance of the sample milk get DT1 and DT2. The conclusion as follow: 1) With the milk’s bacterial total increasing, the DT1 which checking the electromotive force gets is reduced gradually. The reason is that if the cow milk is polluted by the bacteria, along with oxygenic being consumed an the reductive metabolizable production coming out, the redox force is fallen down gradually. So along with the bacterial total of the cow’s milk increasing, its metabolism quickens gradually, the electromotive force reduces more quickly, the time when the value is reached is more short.2) With the milk’s bacterial total increasing, the DT2 which checking the electromotive force gets is reduced gradually. The reason is that when the bacteria reproduce ,the nutrition element (for example the lactose, the protein, the fattiness) of the raw milk, the big molecule substances is coverted to the small molecule substances (lact-salt or ammonia). The milk’s resistance gets reduced. So along with the bacterial total of the cow’s milk increasing, its metabolism quickens gradually, the resistance reduces more quickly, the time when the value is reached is more short.(2)The variety of lactose、fattiness、protein’s content in the raw milk is no influence for the detected results. The DT’s error is between±0.03-±0.07h. The reasons as follow:1) They aren’t quite sterilized, so they are likely to take bacterial. Or when the milk is shared, it is polluted outside. Consequently, the DT become short.2) When the milk is being detected, it is mixed other bacteria, or disturbed from environment(for example the tremble, too high sound). These are the reasons that the error come out.(3) The standard curvilinear is set up and validate experimentantion, the conclusion as follow:1) The research indicates that the detect time DT received by testing sample milk’s resistance and electromotive force with impedance detector is shortened gradually as the aerobic bacterial count increased, that is the high aerobic bacterial count is, the smaller DT is.2) The research indicate that according to the principle of electric impedance detect method, test the electromotive force and resistance in sample milk and receive detect time DT1, make regression analysis with these received data, build standard curve and the regression equation is y? = 10.3671?0.6924x. Make hypothetic test of significance to regression equation and regression coefficients using F detect method, the results are all marked. Receive correlation coefficient r1= -0.9590, that is the relation of aerobic bacterial count and DT1 is high negative correlation.3) The research indicates that according to the principle of electric impedance detect method, test the electromotive force and resistance in sample milk and receive detect time DT2, make regression analysis with these received data, build standard curve and the regression equation is y? = 10.2728?0.6745x. Make hypothetic test of significance to regression equation and regression coefficients using F detect method, the results are all marked. Receive correlation coefficient r2= -0.9481, that is the relation of aerobic bacterial count and DT2 is high negative correlation.4) The research indicates that by the 7 parallel test of three quantitative level, validate the two above regression equation, make hypothetic test by t detect method, the result shows that the aerobic bacterial count detected by the two methods is the same as detected by the method of agar counting. The innovation of this thesis is:Using homemade impedance detector to detect aerobic bacterial count in the raw milk;Using homemade impedance detector to test electromotive force and resistance in raw milk, build two standard curves.
This paper applies project risk assessment theory to oil pipeline risk assessmentpractice. The development and current status of oil pipeline risk assessmenttechnology are generally introduced both at home and abroad. Especially, Kent indexassessment model is analyzed in detail, which nowadays is widely used in pipelinerisk assessment practices in China. Although the Kent model has many advantages,there are some shortcomings especially in weights for the first rank assessmentindexes. Inoriginalmodel,weightsofthefirstrankassessmentindexesaresetequally,which is not consistent with practical situation in China. Reliability engineeringtheory and statistic method are used to improve this shortcoming in this paper. Inordertomakethisimprovementmorefeasible,experts’opinionsshouldbeconsideredlater.In order to solve the problem that assessment results may be distorted by riskestimators’subjectivity, the grey evaluation model is used to assess project risk. Inthis paper, effect analysis on the two whiteness functions is conducted based oncomputer simulation, which are widely used in the grey evaluation model at present.The result shows there are drawbacks in both of them, which make the results of themodel incorrect. Thus, the paper proposes “three-step method” to set linear whitenessfunctions, and re-sets linear whiteness function. It is proved by computer simulationthat this improvement has made better effect. In further study, it is found thatevaluation effect of this model is relavant to power exponent of the whitenessfunction.Based on the study above, whiteness functions with different powerexponents are used when implementing grey evaluation model, which is called”improved grey risk evaluation model”in this paper. Finally, the paper demonstratesthe evaluation process of”improved grey risk evaluation model”through a case ofrisk assessment for gas pipeline, which shows improved model is more accurate andreliable.
From the midst of 1990s, facing the broad market and lower labor cost, many international tyre groups step into china to establish producing bases through the way of single-venture or joint-venture. With the quick increase of market share and development, the china tyre enterprises are facing unprecedent challenge. In such a situation, if a enterprise want to get competitive advantage, he must improve his holistic performance.Facts proves that as the key function of human resource management, performance management is a significant management way to improve enterprise’ s performance. but in fact, there are many problems in many tyre enterprises especially the small and medium-sized enterprises, which blocks their developing.With a full awareness of present Y Co., Ltd’ s operation state and the problems in performance evaluation method, this thesis puts forward a research subject centered on this company’ s key performance index system based on Balanced Score Card theory. In the process of this research, performance management related theories、value chain theory、competitive advantage theory and BSC theory are employed. Through analyzing the method of establishing performance index, the KPI based on BSC theory is put forward. Afterwards in order to implement this system, the process of establishing performance index system is explained.The theory-reality combination approach is utilized to analyze and explain the meaningfulness of designing a KPI system based on BSC theory for this company. Through a comparison analysis and the integration of the core thought of balanced scorecard method and critical success factors method, the key performance index system design method eventually comes to birth. In the design process of this key performance index system, quantitive and qualitative analysis method are introduced to affirm this company’ s differentia strategy through analyzing the company’s macro environment、industry environment and inner environment in order to know the company’s present external opportunities、external threats、internal advantages and disadvantages. The company should focus on the maintenance and exploit of radial tyre market, and keep up the sale on bias tyre. For the other tyre market, the company should exit. On such a position, the present strategy is to input research resource to accelerate the design of new products, which can satisfy the need of customers. Through the good market image and brand reputation, the company can be one of the famous tyre manufacturers. To confirm the company’ s present strategy objectives, the BSC is used to decompound the strategy. the strategy map is used to decompound the strategy objectives and finally the KPI of departments come birth. Through the research of index proportion and appraisal method, the index system is completed. The summary and suggestions are given at the end of the thesis.The thesis aims on designing a strategy-oriented performance management system to integrate the enterprise’s strategic objectives with employee’ s behavior, which will improve the core competency. Also it is expected to be model for other tyre enterprises to study and follow.
The milk performance of yaks with different birth,the contents of protein, fat, lactose, dry matter and ash in the yaks’milk were measured;the content of fatty acid in yaks’ milk fat was tested by.The results were compared with the counterparts of holstein,scalper. The pasture yield of alpine pasture and the nutrient component of the pasture in Tianzhu Tibetan Municipality, Gansu,were studied, too.The milk yield increased with the increase of the yaks’ birth. After fifth birth; the milk yield tended to decrease; the milk yield of third to fifth birth yaks in Nannigou pasture was significantly higher than that of their congener in Daiqian pasture and Wushaoling pasture (P<0.05) ,and the mean milk yield of the former in July and August was higher than that of the two later;the pasture production in Nannigou was higher than those in Daiqian and Wushaoling .The higher milk performance of yaks in Nannigou was attributed to the higher pasture production in the pasture.The contents of fat and protein in yaks’ milk from the 3 pastures were not significantly different(P>0.05 ),while the contents of fat and protein in yaks’ milk were exetremly significantly higher than those of Holstein milk(P<0.01).The contents of fatty acids in yaks’ milk from the 3 pastures were not significantly(P>0.05),indicating that the conditions of the pasture have no effect on the contents of fatty acid in yaks’ milk.The contents of fatty acids in milk of 1 to 5 birth yaks were not significantly different(P>0.05),showing that the different birth yak has the same physiological mechanism of synthesizing fatty acid.Contrasted with the contents of fatty acids of Holstein milk,the contents of unsaturated fatty acids(USFA) in yaks’ milk were significantly higher(P<0.05) and the contents of saturated fatty acids(SFA) in yaks’ milk were significantly lower(P<0.05),resulting from different genes and feeding patterns.The contents of SFA and USFA and the ratio between SFA and USFA were 65.05%,34.95% and 1.86 in fading period. The contents of SFA and USFA and the ratio between SFA and USFA were 63.61%,36.39% and 1.75 in end of fading period. The contents of SFA and USFA and the ratio between SFA and USFA were63.09%,39.02% and 1.62 in buding period. The contents of SFA and USFA and the ratio between SFA and USFA were56.96%,43.04% and 1.32 in flourishing period.With the rising of temperature and the mature of pasture,the contents of SFA in yaks’milk were declining while the contents of USFA were increasing.
In this dissertation, by using the method ofin the lab condition, the domestic sewage was direct aerated in testing equipment. The was cultivated step by step by controlling the environment conditions. During the process of cultivating , the laws of change and biodegradation characteristics of microorganism population were emPH atically analyzed according to the experiment PHenomenon. Observed and analyzed large amount of zoogloeas which appeared during the process of cultivating. The influences of load on main microbe by changing the load were studied.The results showed that: 1. The activated sludge was cultivated successfully in lab by controlling the environment conditions. The microbe evolved from low-grade to high-grade during the process of cultivating. 2. During the process of cultivating, the effluent quality indexes changed with the change of main microbial community. At the early stage of cultivating, the free cells were the main microbe. The effluent effect was not good. The removal rate of COD is 40%, of BOD is 26.6%. The sludge settleability was not good enough in Aeration Tank, the value of SV30 is 1.3%.At the medium stage of cultivating, the swimming type of ciliates were the main microbe. The structue of sludge is compacter than at the early stage of cultivating. The effluent effect was improving. The removal rate of COD is 60%, of BOD is 64.5%. The sludge’s SV30 in Aeration Tank is 5%. At the late stage of cultivating, the Vorticella like protozoan appeared and became the dominant population. It marked the maturity of the activated sludge. The value MLSS achieved 1949.6mg/L. A large amount of branched zoogloeas made the flocs of activated sludge bigger. The removal rate of COD achieved 74%, of BOD achieved 74.2%. The sludge’s SV30 in Aeration Tank is 15%. The efficiency of sewage treatment is good.3. During the process of cultivating activated sludge, s appeared. The removal rate of COD increased remarkably. possesses stronger tolerance for water quality and shock loading ,which can enhance the reversibility of injured activated sludge.4. Observed the influences of changing organic load on main microbe, the results showed that high load can cause the nematode mass rearing, made the sludge abnormal and the effluent quality bad. Branched zoogloea possesses stronger tolerance for water quality and shock loading, so did not change.