Lead là phần quan trọng nhất của bất kỳ tin bài nào, dù đó là tin vắn, tin tổng hợp, bài phân tích hay bài phóng sự. Lead tức đoạn văn đầu tiên (còn gọi là intro) có thể làm cho câu chuyện trở nên hấp dẫn nhưng cũng có thể khiến nó thất bại.
Cần dành nhiều thời gian cho lead: nó phải có khả năng đứng độc lập mà vẫn nêu được câu chuyện, nhưng cũng phải hấp dẫn và làm cho độc giả muốn đọc tiếp. Nếu không làm được điều đó thì không chỉ lead hỏng mà...
Since the maintenance-free sealed nickel/cadmium accumulator became of high importance in the market, in the middle of the 1950s (Figure 17.1), the German battery company Sonnenschein has invented the ﬁrst maintenance-free portable lead-acid batteries in small sizes in modules of 2 to 12 V between 1 and about 30 Ah. These batteries have been absolutely maintenance free and because of their immobilized electrolyte they could be used in any position without leakage.
Mỗi nhân viên sale chuyên nghiệp đều mong muốn có những hot lead, nhưng chỉ một vài người trong số họ là biết cách tìm chúng dễ dàng và thường xuyên. Thay vào đó, hầu hết các sale đều bắt đầu với danh sách của bộ phận marketing – đa phần là những danh sách không có tác dụng. Các nghiên cứu chỉ ra rằng trong những danh sách như thế, cứ 30 mẫu tin thì có 1 mẫu tin là có chất lượng (được khai thác từ khách hàng). Vì vậy, không nghi ngờ rằng hầu hết các sale...
The effect of polyaspartate (PASP) on the performance of the lead-acid negative plate has been investigated. It was established that this polymer additive controls the crystallization process of lead sulphate and modiﬁes the shape and size of PbSO4 crystals. The addition of PASP to the negative paste and to the electrolyte improves the utilization of the negative active material and reduces the internal resistance of the negative plates.
Some years ago a consortium of enterprises and a university from different European countries and industrial sectors was established
to work together in the development of lighter lead–acid batteries for electrical and conventional vehicles with new innovative materials
and process techniques, with the final goal of increasing the energy density by means of a battery weight reduction. Its main idea was to
substitute the heavy lead alloy grids mechanical support of the active masses and collectors of the current produced during the charge
and discharge reactions.
Primary chemically formed lead dioxide (PbO2 ) was used as positive electrode in preparation of lead–acid bipolar batteries. Chemical oxidation was carried out by both mixing and dipping methods using an optimized amount of ammonium persulfate as a suitable oxidizing agent. Xray diffraction studies showed that the weight ratio of -PbO2 to -PbO2 is more for mixing method before electrochemical forming.
In order to meet the increasing demand for valve-regulated lead–acid ŽVRLA. batteries, a new soft lead has been produced by Pasminco Metals. In this material, bismuth is increased to a level that produces a significant improvement in battery cycle life. By contrast, other common impurities, such as arsenic, cobalt, chromium, nickel, antimony and tellurium, that are known to be harmful to VRLA batteries are controlled to very low levels. A bismuth ŽBi.-bearing oxide has been manufactured ŽBarton-pot method. ...
The use of red lead in battery plates is not very well known to a large segment of the lead–acid battery industry. Historically, it was used in
pasted and tubular positive plates in order to improve their formation time and enhance deep-cycle performance. Although the use of red lead
has diminished over the last few decades, many companies are again considering the use of red lead in their plates. This article aims to give
manufacturers a solid knowledge of the properties of red lead, including production and handling methods.
Đề tài Leading change nêu 6 phong cách lãnh đạo của Daniel Goleman (2000) ( Daniel Go leman (sinh ngày 7/1/1946) tại Stockton, California. Ông là một học giả nổi tiếng, một nhà tâm lý học, nhà báo và chuyên gia tư vấn kinh doanh. Goleman đang giảng dạy tại Đại học Harvard.) Daniel Goleman phát triển một bộ sáu phong cách lãnh đạo khác nhau thông qua nghiên cứu thực hiện trên 3.800 giám đốc điều hành trên toàn thế giới.
This study investigated the effects of Na 2 SO4 additive in the positive electrode on the performance of sealed lead-acid cells. The additive Na 2 SO4 in the cured plates can reduce the 4BS crystal size, which produces a smaller a-PbO 2 and b-PbO 2 crystal size in the formed plates, which will have a larger surface area. The plate’s chemical composition is independent of the amount of Na 2 SO4 additive in the positive electrodes. Plate composition relies only on the cure temperature conditions. ...
A new technology for production of 4BS pastes for the positive (lead dioxide) plates of lead-acid batteries has been developed based on an Eirich Evactherm1 mixer. The basic principle of this new technology is that 4BS crystals with dimensions between 20 and 25 mm are formed ®rst from a semi-suspension at a temperature higher than 908C and then the excess water is removed from the semi-suspension under vacuum until the desired paste density is obtained. During the vacuum treatment the temperature of the paste decreases and small 4BS and PbO crystals are formed. ...
Tribasic lead sulfate Ž3BS. and tetrabasic lead sulfate Ž4BS., used as precursors of the positive active material in the leadracid batteries, were prepared by a new method: reactive grinding. The effects of various experimental parameters Žstoichiometry, hygrometry of the starting compounds, duration of mechanical treatment. upon the nature and morphological features of the resulting phase were investigated.
Lead is a rare element present in the earth’s crust in a 1.4 Â 10À3% (w/w). It is a toxic heavy metal that exists only in a cubic close-packed metallic form. It shows the preference for the divalent state with electronic conﬁguration [Xe]4f145d106s2 and low stability of the Pb–Pb covalent bond. Lead(IV) in solution is unstable (electronic conﬁguration: [Xe]4f145d10). The most important Pb ore is galena (PbS). Other lead ores are anglesite (PbSO4), cerussite (PbCO3), mimetesite (Pb5(AsO4)3Cl), and pyromorphite (Pb5(PO4)3Cl). ...
Pb–Ca foil laminated on rolled sheet for positive grid of lead-acid battery is proposed to prevent premature capacity loss (PCL) during charge–discharge cycling. Batteries with Pb–Ca foil laminated on positive grid had longer life during charge–discharge cycle than conventional battery, which failed early by PCL. PCL is a phenomenon due to the increase of the interfacial resistance between the positive grid and the positive active mass (PAM) during discharging by PbSO4 formation in the corrosion layer....
The study looked at the use of red lead in the manufacturing of valve regulated lead acid (VRLA) miners cap lamp (MCL) batteries that were made with either ﬂat plate or tubular positive electrodes. A problem with using only grey oxide in the manufacture of thick ﬂat plate or tubular electrodes is the poor conversion of the active material to the desired lead dioxide.
The innovative solution proposed in this paper to improve both cycling life and performances of a very low cost lead–acid battery is the combination of the compression concept and the use of micro-porous additives added in the active mass.
Organic expanders play an important role in the lead–acid battery. This study presents the design of an electrochemical method which evaluates the influence of some commercial expanders on the performance of the negative plate. Examination is made of different commercial expander formulations which are prepared in the laboratory under carefully controlled conditions.
The effect of fast and three-step charge mode on the capacity and cycle life of lead±acid battery negative plates was investigated using a model mini electrode (ME). It has been found that the charge algorithm exerts a strong effect on the charge acceptance of the negative electrode. In the two-step charging mode I1, j2 with increase of the current at the ®rst step of charge, the capacity of the negative electrode decreases and the cycle life shortens. This phenomenon is reversible as it is probably due to the incomplete reduction of PbSO4 to Pb. The phenomenon is explained...
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