The ABSTRAKTujuan penelitian ini adalah untuk mengetahui kemampuan gelatin, ferro sulfat dan aluminium sulfat serta kombinasi gelatin dengan ferro sulfat atau aluminium sulfat untuk pemisahan krom total (krom valensi 3 dan krom valensi 6) pada limbah cair industri penyamakan kulit. Pemisahan krom total pada limbah cair dilakukan dengan menggunakan gelatin dan ferro sulfat atau aluminium sulfat dengan rasio 4:0; 3:1; 2:2; 1:3; dan 0:4 (b/b). Hasil penelitian menunjukkan bahwa gelatin, ferro sulfat, dan aluminium sulfat, mampu memisahkan kandungan krom total pada limbah cair industri penyamakan kulit. Kombinasi antara gelatin dengan ferro sulfat atau aluminium sulfat sebagai flokulan dapat bersinergi untuk pemisahan kandungan krom total pada limbah cair industri penyamakan kulit. Kombinasi antara gelatin dan aluminium sulfat dengan rasio 3:1 (b/b) dapat memisahkan kandungan krom total sebesar 94,75%, limbah menjadi lebih jernih, dan derajat kekeruhan turun sebesar 74,47%. Kandungan krom total pada limbah pasca pemisahan menjadi sebesar 0,61 ppm. Keadaan ini telah memenuhi syarat baku mutu limbah cair bagi usaha dan khususnya untuk kegiatan industri penyamakan kulit.Kata kunci: gelatin, flokulan anorganik, limbah cair, krom total. PENDAHULUANKrom (Cr) merupakan bahan penyamak kulit yang paling banyak digunakan oleh industri penyamakan kulit dan sekitar 85% kulit dunia disamak menggunakan krom (Bacordit et al., 2014). Hal ini didasarkan pada kenyataan bahwa krom mampu bereaksi dan membentuk ikatan dengan asam amino protein kolagen kulit (Mustakim et al., 2010). Disamping itu, kulit yang disamak menggunakan krom memiliki beberapa keunggulan, antara lain cocok digunakan untuk produksi aneka ragam barang kulit dan kulit krasnya memiliki kesesuaian yang lebih baik dengan bahan kimia untuk proses retanning dan fatliquoring (Wu et al., 2014). Kulit
Conventional timing estimation schemes based on autocorrelation experience performance degradation in the multipath channel environment with high delay spread. To overcome this problem, we proposed an improvement of the timing estimation for the OFDM system based on statistical change of symmetrical correlator. The new method uses iterative normalization technique to the correlator output before the detection based on statistical change of symmetric correlator is applied. Thus, it increases the detection probability and achieves better performance than previously published methods in the multipath environment. Computer simulation shows that our method is very robust in the fading multipath channel. are supporting applications that run in a high speed mobility environment. Recently OFDM technique is also used for cognitive radio systems, which the use of frequency spectrum in the OFDM systems can be done as efficiently as possible [4]- [5]. However, OFDM systems need strict timing synchronization between transmitter and receiver, as an error in timing estimation give rise to InterSymbol Interference (ISI) and can decrease the overall performance of OFDM systems [6]- [7].For symbol timing estimation, Schmidl [8] used a preamble consists of two identical parts for symbol timing estimation. But, the timing metric of Schmidl's method has a plateau, which causes a large variance in the timing offset estimation. To decrease the plateau, Minn [9] proposed a new training symbol with four identical parts. It results a sharper timing metric than Schmidl's method, however, it still has ambiguity due to some side-lobes at a side of the peak correlation region, thus estimation variance is still large. In order to reduce the variance, Park [10] proposed a sharper timing metric using symmetric correlation property of the preamble. Yet, the timing metric of Park's method has two large side-lobes. To eliminate the side-lobes of Park's timing metric, Yi [11] proposed a new preamble structure that has symmetric correlation property. The performance of all the above-mentioned approaches decrease in multipath channel environments.To overcome this problem, Cho [12] proposed a method that exploits statistical change of symmetric correlator. It reduces the multipath channel effect, hence the variance of the timing offset estimation is small. However, Cho's method generates error detection if the correlation magnitude on the first arriving path is much smaller than the strongest path. To overcome this problem, we proposed an iterative normalization technique to the correlator output before the detection based on statistical change of symmetric correlator is applied. Considering the very small correlation magnitude on the first arriving path, we attempt to increase the correlation magnitude on the first arriving path to
Abstract. Spectrum sensing for cognitive radio is a challenging task since it has to be able to detect the primary signal at a low signal to noise ratio (SNR). At a low SNR, the variance of noise fluctuates due to noise uncertainty. Detection of the primary signal will be difficult especially for blind spectrum sensing methods that rely on the variance of noise for their threshold setting, such as energy detection. Instead of using the energy difference, we propose a spectrum sensing method based on the distribution difference. When the channel is occupied, the distribution of the received signal, which propagates under a wireless fading channel, will have a non-Gaussian distribution. This will be different from the Gaussian noise when the channel is vacant. Kurtosis, a higher order statistic (HOS) of the 4 th order, is used as normality test for the test statistic. We measured the detection rate of the proposed method by performing a simulation of the detection process. Our proposed method's performance proved superior in detecting a real digital TV signal in noise uncertainty.
Wastes in the form of skin derivatives from leather tanning industries remain serious problems if not managed properly and quickly, since they can cause environmental pollution. This research aimed at studying the influence of base type and concentration for the hydrolysis of trimmed collagen from pickled sheepskin to the yield and properties of gelatin, as well as the gelatin's potential as flocculant. The hydrolysis of trimmed collagen from pickled sheepskin was performed using KOH or NaOH solution, each with varied concentrations of 1, 2, 3, and 4% w/v, for 16 hours. The extraction of the resulting gelatin was performed using water (2.5 water part : 1 waste part), at 70-80 o C, for 3 hours. The results show that the yield of gelatin from hydrolysis using KOH (16.50-28.60%) is lower than that using NaOH (23.68-34.42%). The water and fat contents of the resulting gelatin were relatively similar, while the protein content from KOH treatment was higher than that from NaOH treatment. Hydrolysis with KOH 1% and NaOH 1% and 2% resulted in gelatin that can be used as flocculant. Hydrolysis with NaOH 2% was the best treatment to produce gelatin as flocculant.
Energy detection is among the most popular spectrum sensing method for spectrum sensing due its low complexity. Unfortunately, its performance is poor at low SNR. In this paper we proposed a spectrum sensing method for cognitive radio network that improves the performance of energy detection.
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