This complex dissociates to supply the Cu ions and the [Cu.sup.2+] ions combine with [S.sup.2-] produced from the hydrolysis to form CuS. From the different reaction time the CuS nanostructures need a longer reaction time of 24 hrs rather than 5 hrs.
In addition, a broad band extending into the near-IR region can be observed, which is characteristic for covellite CuS. The optical band gap is obtained by the following equation, with the help of absorption spectra :
According to the above equation, based on the direct transition as shown in Figure 6, the band gaps of as-obtained CuS are 1.64 eV, 1.65 eV, and 1.64 eV without CTAB for 5 hrs, with CTAB for 5 hrs, and with CTAB for 24 hrs, respectively.
Figure 3 describes an example of data transmission to the mth (m = 1, 2, ..., M) PU with the cooperation of K CUs. The transmit power at the kth CU for data transmission to the mth PU is denoted by [P.sup.m,k.sub.cu] x [[alpha].sub.m,k] and [[beta].sub.m,k], respectively, denote the instantaneous channel gains from the BS to the kth CU and from the kth CU to the mth PU.
In phase 1, the BS transmits a signal to CUs and the mth PU.
The first term of (3) is the received SNR at the mth PU in phase 1 and the second term represents the received SNR of the retransmitted signals from CUs in phase 2.
Our design objective is to minimize the sum of the outage probability of all CUs under the total power constraint.
Clearly, we should allocate equal power to each unit in order to make the sum of outage probability of all CUs minimum, i.e., [P.sub.i] = [P.sub.total]/K.
Interestingly, Smith (1988) extended Smith's (1984) stylized model of CU to incorporate uncertainty, but only considered risk neutral CUs to develop his entire model, thus ignoring the CU orientation/domination issue.
Other works such as Black and Dugger (1981) and Walker and Chandler (1977) have not developed formal analytical models of CUs, but still recognize that a CU orientation is likely to affect the manner it operates or behaves.
The Credit Union National Association, CUNA, provides a quarterly comparison of various savings and loan rates for CUs and banks.
In fact, CUs can influence their growth the most by increasing interest rates for share certificates.